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Publisher: Elsevier   (Total: 3183 journals)

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Showing 1 - 200 of 3183 Journals sorted alphabetically
Academic Pediatrics     Hybrid Journal   (Followers: 38, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 26, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 102, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 28, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 40, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 7)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 6)
Acta Astronautica     Hybrid Journal   (Followers: 436, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 28, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 3)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 11, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 5, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 312, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 12, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1, SJR: 1.793, CiteScore: 6)
Acta Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
Acta Psychologica     Hybrid Journal   (Followers: 26, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access   (Followers: 1)
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 7, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 8)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 18, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 9, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 11, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 23)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 183, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 12, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 17, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 29, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 12, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 12, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 24, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 15, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 34, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 5)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 29, SJR: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 11, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 26, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 13)
Advances in Digestive Medicine     Open Access   (Followers: 12)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Ecological Research     Full-text available via subscription   (Followers: 43, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 29, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 51, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 65, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 21, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 10, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 7, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 26, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 25)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 3, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 37, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 10, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 9, SJR: 0.682, CiteScore: 2)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 21, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 14, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 8, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 24)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.182, CiteScore: 0)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 5)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 27, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 19)
Advances in Pharmacology     Full-text available via subscription   (Followers: 17, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 10)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 6)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 67)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 1, SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 6)
Advances in Space Research     Full-text available via subscription   (Followers: 421, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 13, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 37, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 20)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 15)
Advances in Virus Research     Full-text available via subscription   (Followers: 6, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 53, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 384, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 12, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 475, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 18, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 44, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 4)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 58, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 8, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 12, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 12)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 2, SJR: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 11, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 10, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 53, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 6, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 58, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 63, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 46, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 12)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 37, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 29, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 36, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 50)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 255, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 66, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 32, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 28, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 39, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 7)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 66, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 24, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription   (Followers: 1)
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 5, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 44, SJR: 1.512, CiteScore: 5)
Analytica Chimica Acta : X     Open Access  
Analytical Biochemistry     Hybrid Journal   (Followers: 209, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 13, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 14)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 25, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)
Animal Behaviour     Hybrid Journal   (Followers: 223, SJR: 1.58, CiteScore: 3)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 6, SJR: 0.937, CiteScore: 2)
Animal Reproduction Science     Hybrid Journal   (Followers: 7, SJR: 0.704, CiteScore: 2)

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Similar Journals
Journal Cover
International Journal of Adhesion and Adhesives
Journal Prestige (SJR): 0.926
Citation Impact (citeScore): 2
Number of Followers: 20  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0143-7496
Published by Elsevier Homepage  [3183 journals]
  • Static strength prediction of adhesive joints: a review
    • Abstract: Publication date: Available online 8 October 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): L.D.C. Ramalho, R.D.S.G. Campilho, J. Belinha, L.F.M. da Silva The use of adhesive joints has gathered increasing interest in recent years due to their advantages over conventional bonding techniques, namely lighter structures and decreased stress concentrations. Consequentially, the strength prediction of adhesive joints has been studied extensively. This review aims to describe and compare the most relevant methods for the strength prediction of adhesive joints. These methods can be divided into analytical and numerical methods. Analytical methods are generally limited to initial design evaluations or to simple joints. Numerical methods are more commonly used, especially when joint design is complex. Between the different numerical methods, Cohesive Zone Models (CZM) are the most popular method to predict the strength of adhesive joints. This approach is able to predict the strength of a wide range of joint designs with minimal errors. However, it requires the determination of cohesive laws that generally change depending on different geometrical parameters of the joints. Advanced numerical techniques, such as the eXtended Finite Element Method (XFEM) or Meshless Methods have been used to study adhesive joints, but their application needs improvements before they can be more extensively used.
       
  • Rheology and adhesive properties versus structure of
           poly(acrylamide-co-hydroxyethyl methacrylate) hydrogels
    • Abstract: Publication date: Available online 4 October 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Nadia Baït, Christophe Derail, Ahmed Benaboura, Bruno Grassl This study investigates the relationship between structure, rheological properties and adhesive performances of poly(acrylamide-co-hydroxyethyl methacrylate) P(AM-HEMA) hydrogels. The microstructure and, as a consequence the rheological behavior, of polyacrylamide-based hydrogels have been modulated by varying the precursory reaction mixtures composition. Elastic G’ and loss G’’ shear moduli measurements highlighted their inhomogeneous structure. Structural parameter values predicted by the rubber elasticity theory showed that P(AM-HEMA) networks are constituted by dense polymer regions interconnected by more dilute polymer ones as a result of multiple cross-linking reactions. We demonstrated that increasing the cross-linker composition allows to increase G’ values however the inhomogeneity degree of the networks is higher. Contrarily, HEMA introduction into the feed and the increase of monomers’ composition suppress the extent of PAM network inhomogeneity. Probe test tack experiments evidenced the effect of P(AM-HEMA) structure on the rheological properties and adhesion energy as well as the detachment type.Graphical abstractImage 1
       
  • Optimization and practical application of cottonseed meal-based wood
           adhesive formulations for small wood item bonding
    • Abstract: Publication date: Available online 4 October 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Zhongqi He, Huai N. Cheng, K. Thomas Klasson, Catrina Ford, Vladimir A.B. Barroso The interest in biobased wood adhesives has steadily increased in recent years. Our previous studies have shown that water-washed cottonseed meal (WCSM) could be used as low-temperature and high-solid content biobased wood adhesives for non-structural bonding as European Standard Class D1 adhesives. In this work, we optimized WCSM-based adhesive formulations with high solid contents up to 49% for bonding of small wood items at low temperatures (40 °C). Chemical denaturing reagents guanidine hydrochloride (GdmCl) and sodium dodecyl sulfate (SDS) were added to improve the bonding capability and viscosity of WCSM. Reviewing industry preferences, four formulations with 20% and 30% of WCSM as well as 9.6% and 19.1% of SDS were used to glue “real world” pencil slat sandwiches for pencil making. All the pencils made from these sandwiches bonded at 40 °C and 1 MPa for 120 min passed the Industrial Temperature Cycle test. The results indicated that WCSM could be used as a low temperature wood adhesive, possibly for the domestic furniture and small utensils niche markets. The pencil sandwich bonding represents a specific application that could benefit from the non-toxic glue and also be an example of an interior application.
       
  • A Study on Mixed Fracture Characteristics of Composite Single Lap Joint
           (SLJ) Combining Mixed Continuum Damage Model and Critical Zone Size Based
           Approach
    • Abstract: Publication date: Available online 1 October 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Myong-Ho Kim, Jun-Hyok Ri, Hyon-Sik Hong In this paper, authors present an improved method for predicting the mixed fracture characteristics of composite single lap joint using the mixed - mode continuum damage model and the critical zone size based approach. We apply a method based on the critical zone size to predict the failure of composite adherend and establish a procedure for more precisely calculating the critical zone size using the ABAQUS user subroutine. In addition, a bilinear/exponential mixed - mode continuum damage model is used to evaluate the failure of adhesive of single lap joint. The failure of adherend and the damage process of adhesives can be considered simultaneously by the method based on the critical zone size and the mixed - mode continuum damage model. For the validation of proposed model, the user subroutine of general purpose finite element software ABAQUS was used to simulate the failure process of single lap joint made of fiber reinforced composite materials and the obtained results were compared with the previous experimental results. The results obtained by the method presented in this paper are in good agreement with previous experimental results, and showed that the adhesive cohesive damage process before the global failure of the joint due to the failure of the adherend and the interlayer failure of the composite adherend can be predicted simultaneously.
       
  • Preparation of acrylic pressure-sensitive adhesives by UV/UV step curing
           as a way of lifting the limitations of conventional dual curing techniques
           
    • Abstract: Publication date: Available online 30 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Gyu-Seong Shim, Ji-Soo Kim, Jong-Ho Back, Seong-Wook Jang, Ji-Won Park, Hyun-Joong Kim, Jun-Sik Choi, Jin-Seok Yeom Pressure-sensitive adhesives (PSAs) and UV-curable acrylic systems are widely utilized in different industries, with particular attention currently directed at their use in the production of re-usable modules for smart devices. Herein, we developed a two-step UV/UV curing technique to overcome the limitations of dual curing methods conventionally used for PSA preparation and characterized the thus obtained acrylic adhesives by a range of techniques to determine the uncured marginal portion of the pre-polymer, viscoelastic properties, and adhesive properties (peel and tack). Insufficient primary curing resulted in marked physical property deterioration, while the expression of secondary curing was weak when excessive irradiation energy was supplied. Thus, it was concluded that the physical properties of acrylic PSAs could be controlled by adjustment of primary curing energy.
       
  • Glue wood veneer to wood-fiber–high-density-polyethylene composite
    • Abstract: Publication date: Available online 24 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Yanan Sun, Limin Guo, Yinan Liu, Weihong Wang, Yongming Song Wood-fiber-reinforced thermoplastic plastic composite is a type of environmentally friendly material. However, its application in furniture and interior decoration is limited due to its lack of wood texture. In this work, wood-veneer-facing decoration was explored to beautify the composite’s appearance. Surface planning and slight sanding were applied to wood-fiber–high-density-polyethylene (WF-HDPE) composite. Polyvinyl acetate emulsion was used as adhesive, and the veneer-faced WF-HDPE composite floor was prepared by the hot-pressing method. The bonding line was analyzed with Fourier-transform infrared spectroscopy and scanning electron microscopy. Planning plus sanding treatment removed the HDPE film on the composite surface and exposed the wood fibers to react with the adhesive. The rough surface provided all decorative samples bonding strengths higher than 0.9 MPa. The bond line could stand 63°C water soaking for 3 h without delamination. The hot-pressing temperature exhibited a significant effect on surface bonding strength. The optimized hot-pressing technique included a hot-pressing temperature of 80°C, a hot-pressing time of 10–20 min, and a hot-pressing pressure of 0.2 MPa. With this combination, the surface-decorative veneer retained the beauty of its original color.
       
  • Effect of the initial F/U molar ratio in urea-formaldehyde resins
           synthesis and its influence on the performance of medium density
           fiberboard bonded with them
    • Abstract: Publication date: Available online 24 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Mohsen Khonakdar Dazmiri, Mohammad Valizadeh Kiamahalleh, Ali Dorieh, Antonio Pizzi The formaldehyde to urea molar ratio (F/U) plays an important role on the properties of urea formaldehyde (UF) resins and of the medium density fiber board (MDFs) bonded with them. This work presents a hypothesis that besides the final F/U molar ratio in UF resin preparation, the initial F/U affects both the formaldehyde emission levels and the physico-mechanical properties of the boards. Three initial molar ratios F/U of 1.9, 2.1 and 2.3 in resin synthesis have been examined in this work. The structural changes and thermal curing behavior of UF resins were tracked by 13C NMR and DSC, respectively. At parity of final F/U molar ratio, the resin with initial F/U=2.1 yielded the highest proportion of linear methylol groups, resulted in the best internal bond strength and lowest thickness swelling of the board. A resin synthesized with the initial F/U= 1.9 provided the highest proportion of total methylene linkages, most methylene ether linkage and lowest free formaldehyde, consistently yielding the lowest formaldehyde emission. These results partially explained why UF resins with lower F/U molar ratios showed relatively poor adhesion when used to manufacture wood-based composites. MDFs bonded with a UF resin having the initial F/U= 2.3 had a relatively good performance with the exception of free formaldehyde, but also showed the best storage stability compared to the other resins having lower initial F/U molar ratios.Graphical abstractImage 1
       
  • Adhesion properties of DBD plasma treated nylon 66 fabric- Optimisation of
           plasma process parameters
    • Abstract: Publication date: Available online 19 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Shital S. Palasakar, Ravindra D. Kale, Rajendra R. Deshmukh Optimisation of DBD plasma process parameters for maximising the adhesion between nylon 66 and PU using Design-Expert 10.0. is reported in this paper. Out of various available designs, the Box-Beheken design (BBD) was adopted for optimisation of plasma process parameters and to evaluate the effect of their interactions on wicking, peel off strength and He intensity. Plasma process parameters such as power used for plasma generation, exposure time and distance between the electrodes were selected for optimisation. Analysis of Variance (ANOVA) was used to assess the quality of statistical model fit. Fisher’s F-test, the coefficient of determination and probability values were used to evaluate the quality and model terms. It was observed that plasma power and treatment time are the significant terms affecting the adhesion properties of the plasma treated nylon 66 fabric. Chemical species generated in the plasma zone were monitored online by an optical emission spectrometer (OES). Change in surface morphology was studied by scanning electron microscopy and atomic force microscopy (AFM) Chemical changes on the surface of the plasma treated samples were analysed by X-ray photoelectron spectroscopy (XPS) and the generation of hydrophilic reactive groups is reported.
       
  • Using the Surface Free Energy (SFE) Method to Investigate the Effects of
           Additives on Moisture Susceptibility of Asphalt Mixtures
    • Abstract: Publication date: Available online 18 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Derun Zhang, Rong Luo Conventional methods for evaluating the effects of additives on moisture damage resistance of asphalt mixtures are either empirical or unable to quantify the contributions of material component properties to the overall mixture performance. To overcome these drawbacks, this study proposes a surface free energy (SFE) method to investigate the effects of various additives on moisture susceptibility of asphalt mixtures. One neat asphalt and one acidic gravel aggregate are selected as the test materials along with 6 commonly-used additives: a warm mix asphalt additive, two nano-materials, a hydrated lime, a Portland cement and a non-amine liquid asphalt anti-stripping agent. All the additives are blended with the neat asphalt to fabricate modified asphalt binders. The SFE components of these modified asphalt binders and the gravel aggregates are measured with the Wilhelmy plate method and the vapor adsorption method, respectively. An energy ratio, defined as the ratio of adhesion of asphalt-aggregate to that of asphalt-aggregate-water, is calculated and used to rank the asphalt mixtures that consist of gravel and asphalt binders modified with different additives in terms of their moisture susceptibility performance. In order to validate the proposed SFE method, two mixture moisture susceptibility tests, the modified boiling water test and the indirect tensile strength test, are conducted on loose and compacted asphalt mixtures, respectively. A consistent moisture susceptibility ranking is obtained from the SFE method and the mixture moisture susceptibility tests, which validates the SFE method proposed in this paper can be used to accurately quantify the effects of additives on the moisture susceptibility of asphalt mixtures.
       
  • Effect of thermal cycling on the degradation of adhesively bonded
           CFRP/aluminum alloy joints for automobiles
    • Abstract: Publication date: Available online 18 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Guofeng QIN, Jingxin NA, Wenlong MU, Wei TAN Thermal cycling is one of the representative service environments of automobiles. As epoxy adhesive and resin matrix of CFRP (Carbon Fiber Reinforced Plastics) composites are polymer materials, their properties may change during long-term thermal cycling and thus affect the joint strength of adhesively bonded composites joints. To investigate the degradation mechanism of adhesively bonded CFRP/aluminum alloy joints subjected to thermal cycling, firstly, the chemical transformations of adhesive and CFRP were analyzed by FTIR (Fourier Transform Infrared Spectroscopy), DSC (Differential Scanning Calorimetry) and TG/DTG (Thermal Gravimetric/Differential Thermal Gravimetric), and changes in mechanical properties of adhesive and CFRP were also tested by quasi-static tests. Then the variations of failure strength and failure modes of adhesively bonded CFRP/aluminum alloy shear joints and butt joints after different aging time were investigated. Results show that the Tg (glass transition temperature), thermal stability, failure strength and Young’s modulus of adhesive improved after thermal cycling because of post-curing. The Tg and thermal stability of the CFRP decreased due to surface oxidation, resulting in the decline of surface adhesiveness of CFRP and the appearance of interface failure. Besides, the mechanical performance of the fiber/matrix interface also declined after thermal cycling, which was verified by SEM (Scanning Electron Microscope). The failure strength of shear and butt joints dropped by more than 40% after thermal cycling for 30 days. The degradation of shear joints was mainly caused by the combined effect of thermal stress and post-curing of adhesive as well as interface failure, while the butt joints were also affected by the fiber tear of CFRP.
       
  • Improving the adhesion of glass/polypropylene (glass-PP) and high-density
           polyethylene (HDPE) surfaces by open air plasma treatment
    • Abstract: Publication date: Available online 18 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Vidyarani Sangnal Matt Durandhara Murthy, Uday Vaidya The objective of this study was to investigate the bonding between glass reinforced polypropylene (glass-PP) and high-density polyethylene (HDPE) surfaces. As glass-PP and HDPE surfaces possess low surface energy inherently, atmospheric plasma treatment enhances the adhesion characteristics between the surfaces by increasing their surface energies. Both the materials were subjected to atmospheric/air plasma by varying parameters such as plasma intensity and number of treatments. Optimal plasma treatment conditions were determined based on the bond strength of the materials. Various characterization techniques such as FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), DSC (differential scanning calorimetry) and surface energy determination via wettability inks, were employed to understand the surface modification following plasma treatment. Furthermore, the effect of plasma treatment on glass-PP surface versus a neat polypropylene (neat PP) surface was characterized to understand and establish a baseline. Improvement in bond strength of glass-PP-HDPE panels was observed, (Mode 1 interlaminar fracture toughness) value of glass-PP- HDPE panels increased from 0.1 N/mm to 5.5 N/mm (after plasma treatment) whereas, the GΙc value of neat PP- HDPE panels increased from 0.4 N/mm to 2.8 N/mm (after plasma treatment). Enhancement in the surface energy of glass-PP and HDPE surfaces was observed, surface energy of glass-PP increased from 28 mN/m to 58 mN/m and the surface energy of HDPE surface increased from 28 mN/m to 72 mN/m.
       
  • Experimental investigation on strength of stepwise tailored single lap
           adhesive joint using second-generation acrylic adhesive via shear and
           low-cycle shear tests
    • Abstract: Publication date: Available online 18 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Y. Sekiguchi, M. Nakanouchi, K. Haraga, I. Takasaki, C. Sato Stress concentration in adhesively bonded joints, which is considered a major factor affecting their strength, can be avoided by tailoring the material properties of the adhesives using a functionally graded adhesive (FGA). The material properties of second-generation acrylic (SGA) adhesives can be simply changed by changing the mixing ratio of the agents. However, the superiority of FGA joints using SGA adhesives has not been experimentally clarified yet. Therefore, in this study, a shear strength test and a constant load low-cycle shear test were conducted on single lap joint (SLJ) specimens tailoring the adhesive layer stepwise. The FGA specimen was compared with the non-tailored specimens using stiff or flexible adhesives. The SLJ test results showed 16% improvement in the joint strength by stepwise tailoring of the adhesive layer. Additionally, the difference in the strain distributions among the different adhesive layers was investigated via a digital image correlation (DIC) method, and the shear strain at the edge of the FGA specimen was more than 40% decreased compared to the non-tailored specimen using the flexible adhesive. The low-cycle test results also showed the superiority of the FGA specimen to the other specimens. The FGA specimen held up more than 4 times the number of cycle of other specimens with an applied load of 18 kN or more. This was attributed to the suppressed plastic deformation at the edges of the adhesive layer owing to the introduction of FGAs.
       
  • Deriving 3-propanesulfonic-2-hydroxy substituents in the molecular chains
           for overcoming the drawbacks of oxidized cassava starch
    • Abstract: Publication date: Available online 18 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Wei Li, Jie Wu, Dayin Hou The objective of this study was to improve paste stability, adhesion-to-fibers and film performances of oxidized cassava starch (OCS) for ameliorating end-use issues in various applications. For this purpose, a starch derivative with 3-propanesulfonic-2-hydroxy (PSH) substituents was prepared by an etherification of OCS with a 3-chloro-2-hydroxy-1-propanesulfonic acid sodium salt. The etherified OCS (EOCS) granules were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy techniques. Viscosity stability was investigated by measuring the change of viscosity over a period of time. Adhesion was evaluated by a legal method (FZ/T 15001-2008). Film performances were also studied in terms of tensile strength, percentage elongation at break, flex-fatigue resistance and degree of crystallinity. The successful introduction of PSH substituents was not only able to improve the stability of OCS, enhance its bonding forces to cotton and polylactic acid (PLA) fibers, but was also capable of increasing the elongation and flex-fatigue resistance of the film and decreasing its tensile strength and degree of crystallinity, thereby obviously stabilizing paste viscosity, improving the adhesion and lessening film brittleness. With the increase in the etherification extent, the gradually increased stability and adhesion, and a reduced film brittleness were exhibited. The EOCS displayed potential in the applications of cotton and PLA sizing.
       
  • Small scale tests on the performance of adhesives used in cross laminated
           timber (CLT) at elevated temperatures
    • Abstract: Publication date: Available online 18 September 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Samuel L. Zelinka, Ken Sullivan, Shiling Pei, Noah Ottum, Nathan J. Bechle, Douglas Rammer, Laura E. Hasburgh This study is part of a research project examining fire risk in cross laminated timber (CLT) buildings. “Delamination”, a major concern for CLT fire safety, can occur when the adhesive bondline fails in the panel before it chars which can lead to additional fuel for fire regrowth. Understanding the mechanical strength and stiffness of the adhesive bond under elevated temperature is one of the fundamental steps towards better understanding delamination. In this study, the material properties of wood and wood adhesive bonds are studied at various temperatures levels below the char temperature of wood (300°C) to characterize the loss in strength and stiffness as a function of temperature. Four adhesives, three of which are commonly used in CLT production, were studied: two formulations made from polyurethane, one made from melamine formaldehyde, and one made from phenol-resorcinol formaldehyde. Tests were performed in a half-lap shear joint and compared against a specimen with identical geometry made from a solid piece of wood with no joint. The phenol-resorcinol formaldehyde joint had approximately the same shear strength as solid wood at all temperatures, whereas the other adhesives had noticeable reduction in strength at high temperatures. The method presented herein is unique among other CLT adhesive tests as it measures the performance of the adhesive under heat and load.
       
  • Effect of surface contamination on the durability and strength of
           stainless steel – polyisobutylene pressure-sensitive adhesive bonds
    • Abstract: Publication date: Available online 29 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Anna V. Kostyuk, Viktoria Y. Ignatenko, Sergey V. Antonov, Sergey O. Ilyin Cleaning of substrate’s surface with a solvent is a standard step in a procedure of adhesive joints preparation while carrying out adhesion tests. However, is cleanliness of substrates really so important' The effect of contamination of substrate’s surfaces with vegetable (sunflower) and mineral (naphthenic) oils on the strength and durability of adhesive joints formed by neat and organoclay-filled polyisobutylene-based PSAs with a stainless steel substrate was studied. For the filled composition, the strength of the adhesive joints was higher, even with the contaminated surface, than for the system with the neat PIB. Contamination of the surface leads to the formation of a weak layer of plasticized polymer, which contributes to decreasing of the adhesion strength and durability. These parameters, however, are restored over time, which could be connected with the absorption of the contaminants by the adhesive material, as a result of polymer swelling, and their migration to the bulk of the adhesive. The ability of contaminants that can be absorbed and removed from the surface into the bulk of the adhesive is determined by their solubility in the adhesive. It was demonstrated using laser microinterferometry method that PIB is miscible with naphthenic oil, whereas PIB − sunflower oil system exhibits upper-critical-solution-temperature behavior. These observations provide an explanation to the growth trends of durability and strength of the joints over time in the cases of sunflower and naphthenic oil contamination of the substrate’s surface.
       
  • Preparation and characterization of a polyester-etheramide hot melt
           adhesive system from renewable resources
    • Abstract: Publication date: Available online 27 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Karan Chugh, Ganesh Phalak, Shashank Mhaske A polyester-etheramide (PEEA) based hot melt adhesive (HMA) was successfully designed containing a high content of renewable mass. The PEEA HMA was synthesized based on dimer acid (DA), ethylenediamine (EDA), karanja oil and resorcinol. Karanja oil was reacted with diethanolamine to prepare N-N-bis (2-hydroxyethyl) karanja oil fatty amide (HEKA). Resorcinol was reacted with DA with varying concentrations of resorcinol of 0%, 5%, 10% and 15% on a molar basis. The effects of resorcinol and HEKA on the properties of the hot melt were investigated. The synthesized products were characterized by end group analysis, FTIR, DSC, XRD and the rheological, adhesion and mechanical properties assessed. It was observed that the mechanical and thermal properties increased with increasing concentration of resorcinol. These HMA materials could hold potential for sustainability and high adhesive performance.
       
  • Mechanical performance and failure behavior of miniature aluminium joints
           with novel interlocking reinforcement
    • Abstract: Publication date: Available online 27 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): M. O'Brien, D.J. Mortell, M.C. Corbett, R.M. O'Higgins, C.T. McCarthy A novel hybrid joining method is proposed which consists of adhesive joints reinforced with mechanically interlocking surface features. The present work focuses on single interlocking features formed in the centre of the bond region of miniature single lap joints. The joints were loaded under single lap shear conditions to examine the interlocking feature’s effect on joint failure load and work to failure. Results indicate that significant improvements of up to 27% and 542% are obtained in joint failure load and work to failure, respectively. These improvements are caused by the feature altering the stress states present in the adhesive, impeding crack propagation through the bond line and creating a more progressive failure path as compared to a standard flat bonded joint.
       
  • Polybenzimidazole adhesive bonded aluminum-2024 joints for structural
           applications
    • Abstract: Publication date: Available online 27 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): M.F. Shahzad, M.P. Mughal, H.M.S. Iqbal, N.A. Mufti, M.Q.Saleem In the present research, efforts are made to optimize the curing process and bonded joint strength of aluminum 2024 alloy (Al 2024-T3) using polybenzimidazole (PBI) adhesive. Substrate surfaces were prepared using P120 and P1000 sand papers followed by cleaning with ethanol. Substrate surfaces were also prepared using tri-Sodium phosphate (TSP) and the Forest Product Laboratory (FPL) method. Contact angle measurements of untreated surfaces revealed that ethanol cleaned Al 2024-T3 strips exhibited a water contact angle of 86o. A significant decrease in the water contact angle for Al 2024-T3 was noticed with P1000 sanding followed by TSP treatment. The water contact angle of Al 2024-T3 was reduced from 86o to 52o using a combined surface treatment of P1000 sand paper and TSP solution. Lap shear tests were performed to evaluate the single lap shear strength of PBI bonded Al 2024-T3 joints. A maximum lap shear strength of 11.9 MPa was achieved for samples which had received a combined surface treatment of P1000 sand paper and TSP solution. A lap shear strength of 12.1 MPa was achieved using the FPL treatment method. This lap shear strength is almost similar as attained with TSP treated bonded joints. Therefore, the current work also proved TSP as an effective alternative to the hazardous chromate based FPL method for the surface pre-treatment of Al 2024-T3. Fractured surfaces of adhesive bonded joints revealed both adhesive and cohesive failure.
       
  • PEG-based epoxy and epoxy/silica networks: Thermal, mechanical, and
           thermo-mechanical investigations
    • Abstract: Publication date: Available online 27 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Aziz Ahmadi-Khaneghah, Mehrdad Omidi-Ghallemohamadi, Hossein Behniafar A diglycidyl ether resin and an amine hardener, both based on polyethylene glycol (PEG) were synthesized and utilized for preparing new epoxy thermosetting materials. Two popular monomers, i.e. diglycidyl ether of bisphenol A (DGEBA) and/or isophorone diamine (IPDA) were also utilized. Three transparent and rubber-like films were fabricated through one combinational and two non-combinational manners. In the combinational manner, diglycidyl ether of PEG (DGEPEG) and DGEBA with equal moles were cured with equal moles of amine-functionalized PEG (APEG) and IPDA. In the non-combinational manners, at one time, the PEG-based resin was cured with IPDA hardener, and at the other time, DGEBA resin was cured with PEG-based amine hardener. Stoichiometric amounts of epoxy resin and amine hardener were used in all of the curing processes. Three epoxy/silica nanocomposites with silica-loading of 5.0 wt.%, and with the same epoxy matrices were also synthesized similarly. Silica nanoparticles were organically modified and amine-functionalized prior to use. The neat epoxy networks and their silica-loaded nanocomposites were characterized by FT-IR, and FE-SEM techniques. The structure and composition of the six networks obtained significantly affect their thermal, mechanical, and thermo-mechanical behaviors. These influencing factors were fully investigated by thermogravimetric analysis, tensile testing, and dynamic mechanical analysis.
       
  • Peel testing of a packaging material laminate studied by in-situ X-ray
           tomography and cohesive zone modeling
    • Abstract: Publication date: Available online 24 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Simon Pettersson, Jonas Engqvist, Stephen Hall, Nils Toft, Håkan Hallberg Peel testing is used to study adhesive fracture in packaging material laminates. The focus is on improved understanding of the mechanisms that provide a laminate’s adhesive properties, as measured by standard macroscopic tests. Using a specially-designed peel test load rig, peel tests are performed in-situ in a laboratory X-ray tomograph. The peel test results are analyzed using a combination of theoretical models for the adhesive fracture and 3D finite element simulations based on a cohesive zone model approach. Complementary experiments are performed to characterize the properties of the peel arm material. Relaxation of the material is found to occur during image acquisition in the in-situ tests. Despite this, it is possible to obtain 3D reconstructions with good quality during peeling. Peel test properties like the peel arm’s root rotation angle and peel arm thinning are quantified. In the present 90° peel tests, it is found that the delamination progresses in an inhomogeneous manner, with the edges delaminating before the center. A number of issues and mechanisms during the peel test are identified. As an example, the peel arm itself can sometimes split, leaving residues of adhesive on the substrate surface. Such phenomena indicate the ambiguities involved in assessing adhesion properties from standard macroscopic force-displacement measurements, without accounting for the mechanisms involved on finer length scales.
       
  • Synthesis and characterization of lignin-polyurethane based wood adhesive
    • Abstract: Publication date: Available online 23 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Ravindra V. Gadhave, Pratik SanjivKasbe, Prakash A. Mahanwar, Pradeep T. Gadekar The present work aims to evaluate the influence of addition of kraft lignin in moisture curing polyurethane (PU) based wood adhesives. The mechanical, thermal properties and chemical structure of the adhesive were studied. The lignin-PU adhesives were obtained by replacing 1%, 3% and 5% of polypropylene glycol (PPG) by Kraft lignin and further reacted with monomeric diphenylmethanediisocyanate (MDI). The aliphatic hydroxyl level of lignin was not taken into consideration in the stoichiometry, in order to find out effect on % free NCO of the final product. The chemical structure of the synthesized lignin-PU adhesives were analyzed by Fourier transform infrared spectroscopy (FTIR). The lap shear strength of the adhesives was tested by bonding canarium wood substrates. The results illustrated that by increasing the weight % of lignin in such lignin-PU adhesives, a decrease in the free isocyanate content, leading to slower setting time but higher shear strength values, were observed. Similarly, the thermal properties of lignin-PU adhesive were also studied, showing an increase in glass transition temperature (Tg) with increase in lignin content.
       
  • Investigation of an ambient temperature-curable soy-based adhesive for
           wood composites
    • Abstract: Publication date: Available online 23 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Peitao Zheng, Qinzhi Zeng, Qiaojia Lin, Mizi Fan, Jianhui Zhou, Jiuping Rao, Nairong Chen Soy-based bio-adhesives are considered as potential substitutes for formaldehyde-based wood adhesives due to their environmental safety and broad availability. However, high curing temperatures (120-180°C) makes them less energy efficient for wood processing. In the present study, an ambient temperature-curable soy-based adhesive was prepared via the emulsion polymerization of soy flour and styrene. The results of Fourier-transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1HNMR) confirmed that N-methylolacrylamide had grafted onto the soy flour components, and subsequently copolymerized with styrene. The developed soy-based adhesive achieved a wet shear strength of 1.04 MPa with 5% styrene and 8% pMDI, which exceeded the bonding strength requirements of plywood for exterior applications. Soy flour components are essential for this ambient temperature-curable adhesive system. The emulsion soy-based adhesive facilitates moisture evaporation at ambient temperature, and polymeric methylenediphenyl diisocyanate (pMDI) was introduced to produce a crosslinked structure with high water resistance and thermal stability. The soy-based adhesive developed in this study showed great potential in wood composites thanks to its high performance and low curing temperature.
       
  • Evaluation of a structural epoxy adhesive for timber-glass bonds under
           shear loading and different environmental conditions
    • Abstract: Publication date: Available online 19 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Ziga Unuk, Andrej Ivanic, Vesna Zegarac Leskovar, Miroslav Premrov, Samo Lubej This article presents a study of timber-glass adhesive joints. It examines the shear specimen and shear tools preparation process and the evaluation of the results backed up with an overview of existing similar studies. The chosen adhesive was a cold-curing two-component structural bonding epoxy resin (Mapei Adesilex PG1). The shear tests were performed under different temperatures and the timber samples had different moisture contents. A simple shear test tool was designed and was clamped into a universal testing machine for the shear test. The force and crosshead displacement values from the universal testing machine were used for evaluating the results. The environmental conditions of 20 °C and 5 % timber moisture content resulted in the highest average shear strength obtained from the shear tests of the analysed joints (9.89 MPa), whereas the environmental conditions of 50 °C and 20 % timber moisture content resulted in the lowest average shear strength (3.42 MPa). It was found that the joint strength is dependent on the environmental temperature and timber moisture content. Moreover, the shear specimen load-displacement behaviour at the environmental temperature of 50 °C was linear and nonlinear – depending on the timber moisture content. The most frequent failure type was timber failure. Additionally, a nonlinear contact finite element analysis was performed to demonstrate the additional shear specimen rotation due to the clearance between the shear specimen and shear tools. This impact was evaluated regarding the stress distribution in the bond line. The evaluated epoxy resin adhesive was proved to be suitable for timber-glass bonds.
       
  • Tensile behavior of hybrid multi-bolted/bonded joints in composite
           laminates
    • Abstract: Publication date: Available online 19 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Farid Gamdani, Rachid Boukhili, Aurelian Vadean In composite structures, the strength of a standard single-lap joint with multiple bolts at best matches the strength predicted by the standard open-hole tension (OHT) test, which is about 50% of the tensile strength of the unnotched material. Although bonded joints do not have such limitation, they carry other drawbacks. The advantages of bolting and bonding may be combined in hybrid/bonded-bolted (HBB) joints. This study investigates HBB joints using carbon and glass-fiber reinforced composites with up to three bolts. It is found that multi-bolt specimens with or without adhesive fail in net-tension at the outer bolts like in OHT tests. However, HBB joint is not anymore limited by the OHT strength. The addition of the adhesive increases the strength of a three bolts joints by 70% for cross-ply laminates and 30% for quasi-isotropic laminates. The synergy between the bolts and the adhesive in the HBB system is interpreted by the fact that the outer bolts limit peel stresses and concurrently, the adhesive reduces the stress concentration around the bolts. This is particularly important for the cross-ply configuration where the stress concentrations around the holes are high. Other features observed suggest that for multi-bolted HBB joint, only external bolts are needed. Such joint configuration combines the safety provided by the bolts and the efficient load transfer provided by the adhesive.
       
  • Thermo-fracture analysis of composite-aluminum bonded joints at low
           temperatures: Experimental and numerical analyses
    • Abstract: Publication date: Available online 15 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): A. Rahmani, N. Choupani, H. Kurtaran Adhesive joints have found extensive applications in aerospace structures, because of important advantages such as uniform stress distribution, thermal, acoustic and electrical insulation as well as capability of joining dissimilar materials. These joints in aerospace structures frequently experience severe low temperatures. Lack of experimental data in this field motivated the study of the fracture of adhesive joint at low temperatures in this paper. Fracture parameters of carbon-fibre-reinforced polymer-based composites (CFRP) and aluminum bonded joints were investigated in a temperature range of –80 to +22°C. In order to understand the mechanical behaviour of different components of the bonded joint, firstly, the components (adhesive, composite, and aluminum) were characterized by conducting tensile tests. Subsequently, specimens of cracked bonded joint were tested at low temperatures in different loading modes (mode I, mode II, and mixed mode I/II). The finite element model of the bonded joint was developed in order to obtain the dimensionless functions of stress intensity factors at lower temperatures. The results showed that a reduction in temperature down to a particular value contributes to improved critical stress intensity factors, while any further reduction in the temperature tends to lower the critical stress intensity factors, eventually leading to decreased fracture energy absorption capacity of the structure. In the final section of this paper, a study on fracture surfaces and fracture mechanisms was performed via macroscopic and scanning electron microscopic (SEM) analyses.
       
  • Influence of addition curing silicone formulation and surface aging of
           aluminum adherends on bond strength
    • Abstract: Publication date: Available online 12 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Artur Kochanke, Julian Nagel, Christoph Üffing, Andreas Hartwig In spite of many studies, knowledge about the fundamental factors influencing adhesion between addition curing silicones and aluminum substrates is very limited. The aim of this publication is to evaluate the influence of the formulation and the surface state of the adherend on bond strength. For this purpose, the composition of an addition curing silicone was systematically varied and the effects on both material and bond properties were examined. Additionally, the influence of surface aging at different humidities (0 % r.h., 34 % r.h., 82 % r.h.) of acid etch pretreated aluminum substrates was considered. It is shown that the mechanical properties of the silicone material can be easily adjusted over a wide range by changing the formulation. Although high tensile strengths up to 9.2 MPa for the silicone material can be achieved, lap-shear strengths remain moderate at approximately 3.5 MPa. Predominant adhesive failures show the limited adhesive strength of the basic formulation without additives. Basic ingredients of addition curing silicones without additives are able to reach a certain adhesive strength. However, this strength was quite limited and adhesion promoters are required to further improve adhesion. The humidity at which the pretreated substrates are stored has an overall minor influence on bond strength. Surprisingly, bond strength tends to increase with the storage time of aluminum substrates despite lower surface energies in comparison to freshly pretreated substrates. All in all, the storage conditions of aluminum had a rather small influence on adhesion, whereas the composition of the silicone adhesive strongly influences bond strength.
       
  • Properties and characteristics of novel formaldehyde-free wood adhesives
           prepared from Irvingia gabonensis and Irvingia wombolu seed kernel
           extracts
    • Abstract: Publication date: Available online 8 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): A.O. Alawode, P.S. Eselem Bungu, S.O. Amiandamhen, M. Meincken, L. Tyhoda1. There is renewed interest in the domestication of Irvingia tree species due to the potential use of various parts of the tree as raw materials for a wide range of applications such as biodiesel production, cosmetics, perfumes, soap, weight-loss supplement etc. The current study investigates the properties of extracts from the seed kernels of two Irvingia species – Irvingia gabonensis (IG) and Irvingia wombolu (IW) as natural wood adhesives. Three extraction methods using various solvent/solute media were compared in terms of yield, composition and mechanical properties. Statistically, the analysis revealed significant differences between the different extraction methods. The adhesion properties of the extracts were tested on wood veneers according to the American Society for Testing and Materials standard (ASTM D – 906-64). The shear strength of the extracts ranged from 0.55 to 1.5 MPa and 0.86 to 1.7 MPa for IG and IW, respectively. The initial decomposition temperature of all Irvingia Kernel extract ranges from 138.3 – 149.11 oC for IG and 129.5 – 145.3 oC for IW. As a result, the hot melt temperature for the adhesive experiments was set around 150 oC. The results indicate that Irvingia kernel extract is a more promising source of non-formaldehyde based adhesives in wood composite production.
       
  • Effect of Sodium Hypochlorite on Adhesive Charactersitics of Dentin: A
           Systematic Review of Laboratory-Based Testing
    • Abstract: Publication date: Available online 6 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Ensanya A. Abou Neel, Jonathan C. Knowles, Laurent Bozec ObjectiveThe purpose of this review was to systematically summarize the outcomes of laboratory-based studies investigated the effect of sodium hypochlorite application on bond strength of dentin to various materials.DataA comprehensive literature search was conducted using PubMed, Google Scholar, Cochrane Library and OpenThesis database. Then a manual search was also carried out for references from identified articles.SourcesThe search followed the “Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)” statement. Two independent reviewers evaluated the collected studies for their eligibility according to the inclusion and exclusion criteria. Data abstraction and evaluation of risk of bias was then performed.Study SelectionA total of 164 articles were assessed for eligibility. Only 69 met the inclusion criteria. Most included studies presented a low (15.9%) to medium (68.1%) risk of bias. Only 15.9% presented high risk of bias. Because of heterogeneity of the included studies, Meta-analysis was not performed.ConclusionThe outcome from low or high risk of bias studies revealed that sodium hypochlorite has no effect on bond strength of coronal or root canal dentin. While that from medium risk studies showed a reduction in bond strength of dentin.
       
  • Intensity of singular stress field (ISSF) variation as a function of the
           Young’s modulus in single lap adhesive joints
    • Abstract: Publication date: Available online 6 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Pedro Galvez, Nao-Aki Noda, Rei Takaki, Yoshikazu Sano, Tatsujiro Miyazaki, Juana Abenojar, Miguel Angel Martínez Employing mixed adhesive joints has been proven to be very useful. This type of joint leads to improved performance by increasing strength and decreasing stresses in critical areas of the joint. In the same way, the use of the Intensity of Singular Stress Field (ISSF) has been shown to be suitable for adhesive joint calculation, since the adhesive strength can be controlled by the ISSF at the interface end. Four finite element models have been created by combining two epoxy adhesives with different mechanical properties, and therefore with different Young’s moduli. New mixed adhesive joints have been compared with respect to only-one adhesive joints in terms of the ISSF. The results show a clear improvement with one of the configurations of mixed adhesive joints. A significant decrease of 35.64% in the ISSF is obtained compared to the only-one adhesive configuration.
       
  • Metallic Multi-Material Adhesive Joint Testing and Modeling for Vehicle
           Lightweighting
    • Abstract: Publication date: Available online 5 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Brock Watson, Yogesh Nandwani, Michael J. Worswick, Duane S. Cronin While adhesive bonding has been shown to be a beneficial technique to join multi-material automotive bodies-in-white, quantitatively assessing the effect of adherend response on the ultimate strength of adhesively bonded joints is necessary for accurate joint design.In the current study, thin adherend single lap shear testing was carried out using three sheet metals used to replace mild steel when lightweighting automotive structures: hot stamped Usibor® 1500 AS ultra-high strength steel (UHSS), aluminum (AA5182), and magnesium (ZEK 100). Six combinations of single and multi-material samples were bonded with a one-part toughed structural epoxy adhesive and experimentally tested to measure the force, displacement across the bond line, and joint rotation during loading. Finite element models of each test were analyzed using LS-DYNA to quantitatively assess the effects of the mode mixity on ultimate joint failure. The adherends were modeled with shell elements and a cohesive zone model was implemented using bulk material properties for the adhesive to allow full three-dimensional analysis of the test, while still being computationally efficient.The UHSS-UHSS joint strength (27.2 MPa; SD 0.6 MPa) was significantly higher than all other material combinations, with joint strengths between 17.9 MPa (SD 0.9 MPa) and 23.9 MPa (SD 1.4 MPa). The models predicted the test response (average R2 of 0.86) including the bending deformation of the adherends, which led to mixed mode loading of the adhesive. The critical cohesive element in the UHSS-UHSS simulation predicted 85% Mode II loading at failure while the other material combinations predicted between 41% and 53% Mode II loading at failure, explaining the higher failure strength in the UHSS-UHSS joint.This study presents a computational method to predict adhesive joint response and failure in multi-material structures, and highlights the importance of the adherend bending stiffness and on joint rotation and ultimate joint strength.
       
  • Influencing factors, repeatability and correlation of chamber methods in
           measuring formaldehyde emissions from fiber- and particleboards
    • Abstract: Publication date: Available online 5 August 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Venla Hemmilä, Bettina Meyer, Annelise Larsen, Harald Schwab, Stergios Adamopoulos Recently, there has been focus on lowering emission levels of wood-based boards. However, the accuracy and correlation between EN 717-1 and ASTM D 6007 chamber methods at emission levels below 0.05 ppm are not well investigated, and information about their correlation to the EN 16516 method is limited. In this paper, the low emission level of interest was determined by measuring emissions from particles, fibers and pressed boards without glue. The effect of analytical methods and edge-sealing on chamber emissions was determined, and accuracies and correlations of the EN 717-1 and ASTM D 6007 chambers were defined at low emission levels (
       
  • Preparation and characterization of self-crosslinking fluorinated
           polyacrylate latexes and their pressure sensitive adhesive applications
    • Abstract: Publication date: Available online 29 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Cheng Fang, Kai Zhu, Xinbao Zhu, Zhongxiang LinABSTRACTSelf-crosslinking fluorinated polyacrylate latexes based on butyl acrylate (BA), fluorine monomer octafluoropentyl methacrylate (OFPMA), self-crosslinking functional monomers acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) were synthesized by a monomer-starved seeded semi-continuous emulsion polymerization process. The latexes and their corresponding films were characterized by laser particle size analyzer, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle goniometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results indicated that the particle size of the latexes and the gel content of the films were both independent of the amount of OFPMA employed. On the other hand, the particle size of the latexes decreased and the gel content of the films increased with the incorporation of AA and HEA as expected. Glass transition temperature (Tg) and the thermal stability of the copolymer were both improved gradually as OFPMA content increased. XPS, AFM and water contact angle measurement indicated that the fluoroalkyl groups had a tendency to enrich on the surface of the films. However, this enrichment of fluorine on the film surface was reduced after the introduction of self-crosslinking functional monomers into the system. Finally, the adhesive property of the latexes was evaluated for application as a pressure sensitive adhesive (PSA).
       
  • Effect of Zinc Chloride Added to Self-Etching Primer on Bond Strengthto
           Caries-Affected Dentin and Chemical-Physical-Mechanical Properties of
           Adhesives
    • Abstract: Publication date: Available online 10 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Campos RMP, Oliveira CAR, Macedo JPC, França FMG, Basting RT, Turssi CP, Silva TM, Gonçalves SEP, Amaral FLB The aim of this in vitro study was to evaluate the effect over time of zinc chloride (ZnCl2) incorporated into the primer of a two-step self-etching adhesive system (Clearfil SE Bond, Kuraray - SE) on long-term microtensile bond strength (μTBS) to caries-affected dentin (CAD), and on flexural strength (FS) and conversion degree (CD) of the adhesive. First, the CD of SE with and without 2% (wt) ZnCl2 solution was evaluated by Fourier transform infrared spectroscopy (FTIR). Then, beam-shaped samples (7mm x 2mm x 1mm) were prepared with the SE primer containing the ZnCl2 solution, to perform flexural strength (FS) tests. For μTBS testing purposes, CAD surfaces were randomly divided into two groups, according to the presence of ZnCl2 powder (2wt%) incorporated into the adhesive system (ZnCl2), or its absence (NT). An additional group consisting of dentin pretreated with a 2% chlorhexidine digluconate (CHX) solution was proposed as a positive control (n = 10). A two-step self-etching system (SE) was applied following the manufacturer's instructions, and restorations of composite resin were built up on the dentin. After 24 hours, the resin-dentin blocks were sectioned into specimens that were submitted to μTBS testing immediately following, or after 12 months of water storage (WS). Both μTBS and FS tests were performed using a universal testing machine (0.5 mm/min). FS and CD data were submitted to the Student t-test, and μTBS data were submitted to two-way ANOVA and Tukey's test (α=0.05). ZnCl2 incorporation had no statistically significant influence on flexural strength (p = 0.88) or conversion degree (p = 566). Regarding μTBS, no significant effect of the double interaction of “dentin treatment” versus “WS period” (p = 0.546) was observed. The bond strength was not affected by the WS period (p = 0.805). The highest mean bond strength was observed for the NT group, which did not differ from the ZnCl2 group. The lowest mean bond strength was observed for the CHX group, which differed statistically from the NT group (p = 0.053). It was concluded that incorporation of ZnCl2 into the SE self-etching primer did not interfere in the bond strength of caries-affected dentin, in regard to failure mode, flexural strength or CD, and had no other beneficial effects.
       
  • Enhancing adhesive joints between commercial rubber (SBS) and polyurethane
           by low-pressure plasma surface modification
    • Abstract: Publication date: Available online 8 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): R. Kapica, J. Tyczkowski, J. Balcerzak, M. Makowski, J. Sielski, E. Worwa The paper presents research on the two-stage process of low-pressure plasma surface modification of a commercial SBS rubber, improving its adhesion to both the polyurethane adhesive in an organic solvent (PU) and the aqueous polyurethane adhesive dispersion (ADPU). The plasma surface modification process was carried out in a flow reactor with parallel plate electrodes, in which plasma was generated by an RF glow discharge (13.56 MHz). In the first stage of the process, the Ar or O2 plasma was used, and then, as the second stage of the modification process, the treatment was performed in H2O plasma. The adhesive properties of the plasma-modified SBS rubber surface were determined using the 180o-peel strength test (PS). These results were correlated with surface properties investigated using contact angle (CA) measurements, FTIR-ATR spectroscopy, XPS spectroscopy and scanning electron microscopy (SEM). The observed improvement in wettability of the plasma modified surface was attributed to the formation of hydroxyl groups, which was confirmed by spectroscopic methods (FTiR-ATR and XPS). The results of the 180o-peel strength test showed, in turn, a clear relationship between the capacity of adhesive bonding and the amount of oxygen groups (mainly the hydroxyl groups) as well as the surface roughness, determined by SEM microscopy. It was also found that the effects of the plasma surface modification of the SBS rubber were stable for at least 72 hours. The results of this work prove that cleaning and etching of the commercial SBS rubber surface in the first stage of its plasma treatment, followed by chemical modification in the second stage, lead to very strong adhesive joints.
       
  • Cure and performance of castor oil polyurethane adhesive
    • Abstract: Publication date: Available online 6 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Nuno Gama, Artur Ferreira, Ana Barros-Timmons Aiming at the development of sustainable materials, in this study, a biobased wood polyurethane adhesive (PUA), derived from castor oil (CO), was synthetized and its properties were compared with a conventional wood adhesive. Different NCO/OH ratios have been used to assess its effect on the properties of the ensuing adhesives. FTIR, and DMA were used to monitor the extent of reaction and the glass transition temperature of the adhesive respectively. In turn, the wood bonding properties of the PUA over time were assessed by lap shear using pine wood specimens. Is was observed that the lap shear strength increases with the increase of the RNCO/OH up to RNCO/OH =2.50. Above this ratio, the adhesive performance decreases slightly, due to the rigidity of the PUA. Comparison with a conventional wood adhesive showed that CO derived adhesives presented similar strength properties but required less time to develop the ultimate bonding strength. The chemical and thermal stability of the most promising CO adhesive was also assessed. Despite being sensitive to the chemical environment, the castor oil derived adhesives presented higher thermal stability than conventional wood adhesives.Finally, the cure process of CO derived adhesives was studied by differential scanning calorimetry and the Kissinger and Ozawa methods were used to determine the activation energy (Ea). The former afforded a value for Ea= 80.55 and the latter Ea=87.07 kJ.mol-1. Moreover, it was observed that the activation energy is dependent on the degree of cure, increasing slightly up to 0.6 and decreasing significantly afterwards.
       
  • Investigation on the effectiveness of silane-based field level surface
           treatments of aluminum substrates for on-aircraft bonded repairs
    • Abstract: Publication date: Available online 6 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Sang Yoon Park, Won Jong Choi The aim of this study was to assess the role of silane-based field level surface treatment processes on aluminum substrate with a film-type epoxy adhesive. Two silane-based surface treatment compositions based on a dilute aqueous solution of GPS (3-glycidoxypropyltrimethoxy silane) and a hybrid sol-gel solution of TPOZ (zirconium n-propaxine) and GPS were used. The surface morphology of the treated aluminum substrates was characterized by profilometry. Contact angle measurement and X-ray photoelectron spectroscopy were carried out to analyze surface wettability, which in turn is related to the surface chemistry and cleaning efficiency for bond performances. Quantitative evaluation of the joint strength and environmental durability presented that two GPS- and TPOZ-GPS based sol-gel coatings improved the initial adhesion and environmental durability, and hence can be considered promising alternative surface treatment techniques to the existing on-aircraft anodizing process for bonded repairs. Finally, observation of the fracture surfaces revealed that a loss of interfacial integrity between the adhesive and aluminum substrate was the dominant mechanism behind the permanent loss of adhesion; the loss of interfacial integrity induced the low-strength interfacial adhesion failure mode.
       
  • The role of chemical surface modification for structural adhesive bonding
           on polymers - washability of chemical functionalization without reducing
           adhesion
    • Abstract: Publication date: Available online 6 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Elisa Arikan, Jens Holtmannspötter, Felix Zimmer, Timo Hofmann, Hans-Joachim Gudladt This study investigates the role of surface functionalization to increase adhesion forces on polymers. The effects of two different physical pre-treatment methods (oxygen low-pressure plasma - LPP, vacuum-UV - VUV) are investigated on four different polymer matrices (polyetheretherketone - PEEK, polyetherimide - PEI, polyethersulfone - PES and the epoxy resin RTM6). Polymer surfaces were additionally washed after surface treatment with different polar solvents. Surface chemistry, wettability, and topography were investigated before pre-treatment, after pre-treatment and after washing of the samples using x-ray photoelectron spectroscopy (XPS), contact angle measurements and atomic force microscopy (AFM).The results show, that washing of the samples after pre-treatment lead to a chemical surface condition similar to the initial surface. Interestingly, the tensile bond strength of centrifugal adhesion tensile test (CATT) specimens however remained high. In consequence, the thus far widely accepted understanding of surface functionalization as the dominating factor for adhesion promotion on polymers has to be re-evaluated.
       
  • Lignin-based copolymer adhesives for composite wood panels – A
           review
    • Abstract: Publication date: Available online 5 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Aik Fei Ang, Zaidon Ashaari, Seng Hua Lee, Paridah Md Tahir, Rasmina Halis Lignin is a natural and renewable organic compound that can be easily obtained from spent pulping liquors. It can be used as feedstock for making wood adhesives. Nonetheless, lignins need to be modified to enhance reactivity prior to being used as feedstock for making wood adhesives. Appropriate crosslinkers are also needed to ensure the bonding quality of the lignin-based wood adhesives. In the present review, the drawbacks of using lignins alone as wood adhesives, modifications to enhance the reactivity of lignins and production of lignin-based copolymer adhesives for composite wood panels are reviewed and discussed. The objective of this review is to provide background information about the recent status on the development of lignin-based copolymer adhesives for the production of composite wood panels as well as the future prospects of these adhesives in industry. Several modifications such as demethylation, oxidation, methylolation, phenolation, reduction and hydrolysis have shown promising results for enhancing the reactivity of lignins. Several crosslinkers such as phenolic resin, tannin, polymethylene polyphenyl isocyanate (pMDI), furfural and ethylenimine are capable of copolymerizing with lignins to produce lignin-based wood adhesives. The performance of composite wood panels bonded with modified lignin-based copolymer adhesives have been shown to meet the requirements of relevant standards. The main obstacles for the composite wood panels industry to widely adopt to lignin-based copolymer adhesives are the economic and technical issues. Nevertheless, lignin modification methods are proving to enhance the reactivity of lignins and the optimization in such modification methods would justify the economic issue. Together with the public awareness on the safety, health and environment concerns, the utilization of lignin-based adhesives in the composite wood panels industry is feasible.
       
  • Investigation of a pulsed laser ablation process for bonded repair
           purposes of CFRP composites via peel testing and a design-of-experiments
           approach
    • Abstract: Publication date: Available online 2 July 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): T.H. Loutas, G. Sotiriadis, E. Tsonos, S. Psarras, V. Kostopoulos The present study aims to investigate an automatic material ablation process performed by a pulsed Ytterbium green fiber laser for bonded repair purposes of carbon fibre reinforced composites. The investigated process parameters are the scanning speed, the pulse frequency, the hatching distance and the hatching pattern whereas the targeted objectives are the material removal rate as well as the quality of adhesion as characterized by a novel composite peel test. The use of a green laser, if properly implemented and optimized, turns out to offer a series of advantages. Not only it allows the precise, controllable and automatic -without human intervention-material ablation but it can change the morphology of the CFRP surface through micro-machining effects such as the creation of novel highly regular micro-structural formations that significantly enhance bonding. We provide with experimental evidence that this is not always the case but happens only for specific levels of the process parameters. A design of experiments approach is implemented to search as effectively as possible the process parameters space. We utilize a Box-Behnken four-level factorial design to define the minimum number of experimental trials and build an appropriate test matrix. Analysis of variance is finally implemented to assess the influential parameters. Finally, the set of parameters that optimize the objective of simultaneously high peel strength and material removal rate are identified following a response surface methodology.
       
  • Characterization of odorants in waxes for hot melt adhesives using sensory
           and instrumental analyses
    • Abstract: Publication date: Available online 26 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Philipp Denk, Eva Ortner, Andrea Buettner Waxes are important additives in hot melt adhesives for improving the properties of the final product such as the melting point or viscosity. Up to one third of the formulation of the final product consists of waxes. For this purpose usually polyethylene (PE) waxes or Fischer-Tropsch (FT) waxes are used. Waxes affect the overall smell of hot melt adhesives, and often in a negative way. In our study the overall odor of five different waxes made by different manufacturing methods was characterized in order to classify the samples according to their overall smell. First of all the samples were evaluated by a trained sensory panel at room temperature and after heating to 80°C using descriptive analyses. Then the volatiles responsible for the overall smell of the samples were directly extracted using thermal desorption in combination with cryo-focusing and analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS/O). Moreover, the volatiles in the waxes were recovered using solvent extraction and isolated by solvent assisted flavour evaporation (SAFE). The most dominant odorants were then characterized by GC-O and odor extract dilution analysis (OEDA). Using these approaches 39 odorants having different chemical structures were successfully identified for the first time in waxes used as additives in hot melt adhesives. These odorants included alcohols with tallowy, soapy odor qualities such as 2-methyl-2-decanol, 2-methyl-2-dodecanol, and 1-undecanol, as well as a range of lactones such as γ-decalactone and γ-undecalactone having soapy, peach-like odor descriptions. The attributes of the odorants detected using GC analyses correlated with the descriptive analyses of the human sensory panel. This study indicates that the odor impact of waxes to hot melt adhesives depends on the manufacturing method of each single wax and that there is no clear trend for the preferential usage of PE or FT waxes.
       
  • Time and space dependence of large-scale synthesis of colloidal particle
           with special morphology and tuneable polymer film architecture
    • Abstract: Publication date: Available online 26 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Zheng Su, Hua Wang, Xingyou Tian This paper describes a facile method to control the morphology of polymer colloids and the architecture of polymer film via miniemulsion polymerization. By taking advantage of cyclization between the symmetrical diacrylate cross-linker hexamethylene diacrylate (HDDA) and the pendent vinyl in colloidal particles, the morphology of polymer colloids and the architecture of the after-formed polymer film were able to be well controlled by tuning the loading of cross-linker HDDA and crosslinking time. Four kinds of polymer colloid morphologies and four kinds of film architecture (honeycomb, close-packed, loose-packed, and enhanced-honeycomb) were characterized by TEM. The film formation mechanisms behind them were proposed based on the special and interesting results including Z-average size of the colloidal particles, Mc (molecular weight between crosslinking points) and mechanical properties of polymer film. Our results highly suggested that the morphology of polymer colloids and the polymer film architecture together determine the adhesive properties of the colloidal polymer film. The best of 180°-peel resistance, T-peel resistance and shear resistance of the polymer films were 138.12 N/25mm, 40.98 N/25mm and 25.72 N/cm2 at 2.0 phm, 2.0 phm and 0.4 phm with the same crosslinking time of 90 min, respectively. The proposed method is promising to be scaled up for industrial production due to its well adaptability.Graphical abstractImage 1
       
  • Synthesis and mechanical properties of bio-sourced polyurethane adhesives
           obtained from castor oil and MDI-modified cellulose acetate: influence of
           cellulose acetate modification
    • Abstract: Publication date: Available online 20 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Adrián Tenorio-Alfonso, M. Carmen Sánchez, José M. Franco In this study, cellulose acetate and castor oil have been used to synthesize new eco-friendly alternatives to traditional polyurethane adhesives. First, cellulose acetate (CA) was modified with diphenylmethane-4,4’-diisocyanate (MDI) at different NCO:OH molar ratios, ranging from 2 to 4.53, and then the resulting biopolymers were mixed with castor oil (CO) at 1:1 weight ratio. The fully cured bio-sourced adhesives were rheologically characterized by applying dynamic oscillatory torsional tests at different temperatures (from -30 up to 200 ºC). Furthermore, their adhesion performance on stainless steel and poplar wood substrates was analyzed, by conducting standardized mechanical tests, namely single-lap shear and 180º peel strengths, at room temperature and 100 ºC. Fourier transform infrared spectroscopy-attenuated total reflectance along with differential scanning calorimetry and thermogravimetric analysis were also performed. Above a critical NCO:OH ratio, a thermo-rheological simplicity was found within the whole temperature range considered, being able to apply the t-T superposition principle. However, an increase in the temperature led to a depletion in their mechanical performance, thus reducing their temperature range of application. Thermal and spectroscopic analysis corroborated the complete disappearance of free isocyanate during the first few days of curing, and a segmented structure, typical of polyurethanes. Optimum thermo-rheological behaviour and adhesion performance on wood and stainless steel of the bio-sourced polyurethanes studied were found for NCO:OH molar ratios higher than 3.5, which was related to the higher compatibility between hard and soft microdomains.
       
  • The effect of atmospheric pressure plasma treatment (APPT) on the adhesive
           bonding of poly(methyl methacrylate) (PMMA)-to-glass using a
           polydimethylsiloxane (PDMS)-based adhesive
    • Abstract: Publication date: Available online 20 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): V.Bagiatis, G.W. Critchlow, D. Price, S. Wang In the present study, the effect of atmospheric pressure plasma treatment (APPT) on polymethyl methacrylate (PMMA) substrates was investigated in terms of both the chemical and topographical changes introduced to the polymer surface and its influence on PMMA-to-glass adhesion. The use of a silane-based primer in this bonding system was also studied. The changes introduced to the PMMA surface, as a result of plasma processing, were identified using a combination of: X-ray photoelectron spectroscopy (XPS); atomic force microscopy (AFM), and; contact angle analysis (CA). Degreased only and APPT treated PMMA was then bonded to glass using a polydimethylsiloxane (PDMS)-based adhesive and the influence of plasma processing on adhesion performance was determined using the single lap shear (SLS) test geometry. SLS testing of the as-bonded PMMA-to-glass structures was performed as a function of various PMMA surface treatment conditions, and, after exposure of the bonded joints to multiple temperatures in order to assess the effect of the surface treatment on the strength of these joints. It was found that APPT treatment, with various gas mixtures, lowers the water contact angle of PMMA, and increases its surface free energy. The plasma gases used were argon, helium and oxygen, either on their own or in combination. The chemical composition of the plasma modified PMMA surfaces showed an increase in the level of oxygen present and a corresponding decrease in carbon content, as observed by XPS. Furthermore, AFM indicated a significant change in the topography of the PMMA surface after APPT exposure with a 100-200% increase in mean roughness values with optimised plasma conditions.The above-mentioned physicochemical changes to the PMMA surface led to much improved adhesion of the PMMA-to-glass. APPT treatment improved the strength of the SLS joints from 0.28 MPa to 0.58 MPa. In addition, plasma treated PMMA used in combination with a silane-based primer gave a significant further enhancement in observed adhesion levels with SLS values increasing up to 1.56 MPa. Moreover, the adhesion strength of the bonded samples remained stable after both high temperature exposure at 70°C and temperature cycling with exposure of the bonded joints from -50°C to 70°C. This temperature range had negligible effect on the strength of the adhesive joints after 30 thermal cycles.
       
  • Experimental and numerical investigations of adhesively bonded CFRP
           single-lap joints subjected to tensile loads
    • Abstract: Publication date: Available online 15 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Ligang SUN, Cheng LI, Ying TIE, Yuliang HOU, Yuechen DUAN In this article, both experimental study and numerical simulation are implemented to investigate the tensile performance of adhesively bonded CFRP single-lap joints (SLJs). The study considers 7 different overlap lengths, 5 adherend widths and 3 stacking sequences of the joints. Three-dimensional (3D) finite element (FE) models are established to simulate the tensile behavior of SLJs. The failure loads and failure modes of SLJs are investigated systematically by means of FE models and they are in good agreement with those of experiments, proving the accuracy of finite element method (FEM). It is found that increasing the adherend width can improve the load-carrying capacity of the joint better than increasing the overlap length does and choosing 0° ply as the first ply is also beneficial for upgrading joint’s strength. With respect to failure modes, cohesive failure in adhesive and delamination in adherend take dominant, while matrix cracking and fiber fracture only play a small part. With overlap length increasing or adherend width decreasing, cohesive failure takes up a smaller and smaller proportion of whole failure area, but the opposite is true for delamination. SLJs bonded with [0/45/-45/90]3S adherends are prone to cohesive failure, and [90/-45/45/0]3S adherends are easy to appear delamination. Both shear and peel stress along the bondline indicate symmetrical and non-uniform distributions with great stress gradient near the overlap ends. As the load increases, the high stress zone shifts from the end to the middle of the bondline, corresponding to the damage initiation and propagation in the adhesive layer.
       
  • Strength Improvement in Single Lap Adhesive Joints by Notching the
           Adherends
    • Abstract: Publication date: Available online 12 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): B. Bahrami, M.R. Ayatollahi, M.J. Beigrezaee, L.F.M. da Silva In this study, an easy procedure is proposed to improve the strength of Single Lap Joints (SLJs) by introducing a notch in the adherends right after the overlap length. At first, the effect of different notch parameters on the peel, shear and von Mises stress distributions of the adhesive mid-plane layer is investigated by using the Finite Element (FE) method. The considered parameters are the notch angle, the notch width, the notch depth, and the notch distance from the overlap length. Afterwards, a simple 90-degree notch angle which can be easily manufactured is selected for adherend notching based on the numerical results. In addition, in order to experimentally investigate the effects of different notch parameters on the failure load of adhesive joints, five various notch depths with two different adhesive curing methods are considered. Finally, the experimentally obtained fracture loads are compared with the theoretical ones which are based on the predictions of von Mises stress and peel. The results show that using the adherend notching can significantly improve the load bearing capacity of SLJs. For instance, a simple notch with 20% notch depth ratio can improve the load bearing capacity of the SLJ about 60%.
       
  • Biomimetic approach to tunable adhesion of polyurethane adhesives through
           Fe3+ crosslinking and hydrophobic tween units with balance of
           adhesion/cohesion forces
    • Abstract: Publication date: Available online 11 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Burhan Ates, Suleyman Koytepe, Sevgi Balcioglu, Merve Goksin Karaaslan, Unzile Keleştemur, Selam Gulgen, Onural Ozhan Biocompatible adhesives have some limitations such as weak adhesion and low flexibility. To overcome these limitations, we described multiple strategies to provide strong adhesion and high flexibility through Tweens, chlorogenic acid (CLA) and polyethylene glycol (PEG) by reducing excessive interaction between tissue and the adhesive. We synthesized polyurethane-based adhesives using aliphatic 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI), PEG, CLA and Tween units. Hydrophobic side chains in polymer resulted in lower Tg (-36.95-30.36 °C) which indicated more flexibility. The highest adhesion strengths were found as almost 346 kPa for bare polyurethane and 492 kPa for chelated polymer (PU-T40-CLA-15% (5% Tween 40, 15% chlorogenic acid and 80% PEG 200 containing polymer)) with FeCl3. The addition of Tween units provided more stable structure to polymers which proved with in vitro erosion studies. Relatively low erosion values were seen as 5.7, 5.6 and 8.2% in PU-T40-CLA-5% (15% Tween 40, 5% chlorogenic acid and 80% PEG 200 containing polymer), PU-T40-CLA-10% (10% Tween 40, 10% chlorogenic acid and 80% PEG 200 containing polymer), and PU-T40-CLA-15% (5% Tween 40, 15% chlorogenic acid and 80% PEG 200 containing polymer), respectively. In vitro biocompatibility results showed high cell viability in PU-T40-15% as more than 100%. Overall, our findings indicated that these material designs (PU-T-CLAs) provided to overcome the significant challenges of tissue adhesives by improving the flexible character and adhesive strength of the adhesives.
       
  • Uniaxial ratchetting and low-cycle fatigue failure behaviors of adhesively
           bonded butt-joints under cyclic tension deformation
    • Abstract: Publication date: Available online 8 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Jun Zhang
       
  • Uniaxial ratchetting and low-cycle fatigue failure behaviors of adhesively
           bonded butt-joints under cyclic tension deformation
    • Abstract: Publication date: Available online 8 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Jun Zhang, Hui Li, Hai-Yu Li, Xi-Li Wei Ratcheting and low-cycle fatigue failure behaviors of the adhesively bonded hollow cylindrical butt-joints has been experimentally investigated. A series of uniaxial cyclic tension experiments were carried out under stress-controlled mode. The effects of stress amplitude, mean stress and cycle time on the uniaxial ratcheting response, fatigue damage variable evolution and fatigue life of the adhesively bonded butt-joints were analyzed. The results show that the ratcheting strain, ratcheting strain rate and fatigue damage variable all increase with the increase of stress amplitude and mean stress. The shorter cycle time results in the increase of fatigue damage variable and the degradation of the stiffness of the adhesive material. It is also found that the increase of stress amplitude and mean stress can reduce the low-cycle fatigue life. Meanwhile, the fatigue life increases with the increase of cycle time for the adhesively bonded butt-joints.
       
  • Study on the effect of post curing on the Mode II fracture energy of
           structural adhesive using a parameter identification approach
    • Abstract: Publication date: Available online 8 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Xiao Han, Yuexing Chao, Wei Zhang, Yuezhen Chao, Chengwei Wu In this work, a parameter identification approach was developed based on a combined experimental-numerical approach to determine the optimal set of adhesive parameters in adhesively bonded specimen subjected to various post curing treatments. End-Notched Flexure (ENF) testing was conducted to characterise the Mode II fracture property under both recommended and post curing conditions, providing benchmark data for the numerical analysis stage. Experimental results revealed that Mode II fracture energy was effectively affected by the post curing history, with higher temperature and longer curing duration leading to enhanced fracture resistance. The numerically identified Cohesive Zone Model (CZM) parameters using multi-island genetic algorithm provided good correlation in Mode II fracture energies between Finite element (FE) modelling and experimentally measured values, thus extensive experimental characterisation work to determine the adhesive parameters can be effectively eliminated.
       
  • Influence of a wollastonite microfiller and a halloysite nanofiller on
           properties of thermally curable pressure-sensitive structural adhesives
    • Abstract: Publication date: Available online 5 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Agnieszka Kowalczyk, Krzysztof Kowalczyk, Konrad Gziut, Dominik Nowakowski, Michał Sałaciński A thermally curable pressure-sensitive structural tape (SAT-0) was prepared using an epoxy acrylate copolymer and an epoxy resin and modified with a wollastonite microfiller (SAT-W) and a halloysite nanofiller (SAT-H). Influence of the minerals on self-adhesive features and curing behavior of the tapes as well as on shear strength of aluminum/SAT/aluminum joints has been investigated. Thermally uncured SATs containing the fillers exhibited higher Tg (+5 °C for SAT-H), adhesion (+64% for SAT-H) and tack (+10% for SAT-W) while their cohesion was lower (-22% for SAT-W and -86% for SAT-H) in relation to SAT-0. Moreover, filler addition reduced the shear strength of the Al/SAT/Al overlap joints (-6% for Al/SAT-H/Al and -22% for Al/SAT-W/Al), however, the microfiller-based systems exhibited better crack and fatigue resistance, and higher shear strength after ageing tests than SAT-0 and SAT-H (+100% after thermal ageing, +85% after exposure in a climatic chamber, and +27% after immersion in a fuel).
       
  • Experimental investigation and numerical modelling of the mechanical
           response of a semi-structural polyurethane adhesive
    • Abstract: Publication date: Available online 4 June 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): John Fredrick Berntsen, David Morin, Arild Holm Clausen, Magnus Langseth The use of adhesives in load-carrying structures and components has increased recently, especially in the automotive industry. There has been many studies on structural adhesives, but when it comes to semi-structural adhesives, there is a lack of literature. In this article, a semi-structural two component polyurethane adhesive has been studied experimentally and modelled numerically. It was performed uniaxial tension tests at rates ranging from 10-3s-1 to 10-1s-1. The tests were monitored by two perpendicular digital cameras and a thermal camera. Similarly, uniaxial compression tests were performed at rates ranging from 10-3s-1 to 350s-1, where a split Hopkinson pressure bar (SHPB) was used for the highest rates. The low-rate tests were recorded with high-resolution digital cameras, while a high-speed camera and a thermal camera were used for the SHPB tests. In addition, it was performed notched tensile tests at a low rate to study failure. These tests also served as a validation case for the numerical simulations. A high-resolution camera was used, such that the local strains in the notch could be captured using digital image correlation. The experiments indicated that the adhesive behaved similar as rubbers. Therefore, the Bergström-Boyce constitutive model was applied in the numerical simulations. The overall prediction of the test results was seen to be satisfactory, but the initial stiffness was too high compared to the response measured from the experiments. An investigation of the numerical results indicated that this mismatch was likely linked to the formulation of the inelastic shear rate.
       
  • Analysis of methyl methacrylate adhesive (MMA) relaxation with non-linear
           stress–strain dependence
    • Abstract: Publication date: Available online 24 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Arkadiusz Bula, Marcin Kozłowski, Jacek Hulimka, Błażej Chmielnicki One of the problems regarding high strength and stiffness adhesive connections is the concentration of stresses on the edges of the bond. The use of adhesives characterized by high strength but also greater flexibility would avoid this effect and prevent brittle failure. Therefore, the results of a series of laboratory tests are presented in the paper for a semi-rigid methyl methacrylate adhesive (MMA). The research included quasi-static tensile and relaxation tests of the adhesive at a temperature of 23°C and 50% humidity. Based on the test results, the complex characteristics of the viscoelastic material parameters of the adhesive for different stress levels were determined. The Maxwell model was used to describe the material model of the adhesive during relaxation, for which Prony series were calculated. The work also indicates the approach to numerical modelling using the Finite Element Method (FEM) for selected adhesive, ensuring good convergence of results in the elastic work of the material. Numerical analyses were performed in the ABAQUS software, using material models such as hyperfoam and viscoelasticity. Finally, the relaxation function values obtained during the laboratory tests and numerical analyses were compared and a forecast for longer term function values was presented. The presented results can be used for numerical analysis of adhesive joints with the use of a selected methacrylate adhesive, in the scope of the elastic range subjected to short- or long-term loads.
       
  • Electromechanical admittance based integrated health monitoring of
           adhesive bonded beams using surface bonded piezoelectric transducers
    • Abstract: Publication date: Available online 24 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Mahindra RAUTELA, C.R. Bijudas Adhesive bonded structures are gaining attention in engineering and research communities due to their advantages over conventional joining methods. Non-destructive testing and health monitoring of adhesive bonded structures are challenges requiring focused research. Piezoelectric transducers are used for the actuation and sensing purposes in structural health monitoring procedures. These transducers which are adhesive bonded, get disbonds from the host structure during their service period. Presence of a transducer disbond between the transducer and host structure can be inferred as structural disbond and may produce false alarms. It is necessary that both the types of disbonds are distinguished from each other so that an integrated health monitoring procedure can be developed. This paper presents the use of electromechanical admittance technique for the integrated health monitoring of adhesive bonded beams using surface bonded piezoelectric patches. Electromechanical admittance model for one degree of freedom system is revisited and used as a governing model for the adhesive bonded beams. The analytical results are validated with simulations and experimental results. Conventional non-destructive techniques like X-ray and ultrasonics testing are also employed to justify the use of the electromechanical admittance scheme for disbond detection in the adhesive bonded structures. The electromechanical admittance values (both real and imaginary parts) for three levels of transducer and structural disbonds along with the combination cases are collected from the precision impedance analyzer in a frequency range of 1-30 kHz. Numerical study of coupled-domain harmonic analysis is utilized to study the disbond cases. It is shown that the directional shifting of the electromechanical admittance spectrum distinguishes both the types of disbonds. In addition, artificial neural networks are also employed on electromechanical admittance data from simulations and experiments to predict disbond type and the severity levels.
       
  • Bond integrity of cross laminated timber from Acacia mangium wood as
           affected by adhesive types, pressing pressures and loading direction
    • Abstract: Publication date: Available online 23 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Norwahyuni Mohd Yusof, Paridah Md Tahir, Adlin Sabrina Roseley, Lee Seng Hua, Juliana Abdul Halip, Redzuan Mohammad Suffian James, Zaidon Ashaari Cross laminated timber (CLT) was fabricated from Acacia mangium wood by using phenol resorcinol formaldehyde (PRF) and one component polyurethane (PUR) as binders. The purpose of the study was to evaluate the bond integrity of A. mangium CLT produced using different working parameters. The assemblies were pressed at 30°C for 30 min using three pressing pressures (0.9 N/mm2, 1.2 N/mm2, and 1.5 N/mm2). Delamination and block shear tests were conducted on the CLT according to European Standards, EN 391 and EN 392, respectively. The results revealed that PRF-bonded CLT experienced lower percent delamination compared to that bonded with one component PUR. It appears that a higher clamping pressure i.e. 1.5 N/mm2, is needed to sufficiently bond A. mangium lumbers as indicated by a marked increase in bond shear strength with an increase of pressing pressure. PRF was found to be a more superior adhesive than PUR irrespective of cramping pressure and loading direction. A. mangium wood is relatively dense thus requires quite high pressure, 1.5 N/mm2, irrespective of adhesive used. PRF appears to bond A. mangium wood better compared to PUR with shear bond strength of 21% and wood failure percentage of 220% higher.
       
  • Effect of different aging conditions on the shear performance of joints
           made between GFRP and glass with a UV absorbance coating
    • Abstract: Publication date: Available online 23 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Tiziana Alderucci, Marco Rossi, Gianluca Chiappini, Placido Munafò In this experimental study, a series of tensile tests were conducted on double-lap specimens, where UV absorbance laminated glass was adhesively bonded on GFRP polyester pultruded support. Three different types of adhesives were compared, two epoxy and one polyurethane, and both un-aged and aged conditions were investigated. Three ageing conditions, simulating the external environment exposure, were investigated, i.e. temperature/moisture changes (continuous condensation), UV exposure, temperature/moisture changes and UV exposure, in order to test the effectiveness of the UV absorbance film and the durability of the bonding system. This experimental campaign aimsto verify if the UV film affects the compatibility of the bonding system between GFRP and glass to be used for structural applications.The experiments showed that the PU adhesive is not the most suitable for structural applications, since it shows a great deformability of the joint with a very small stiffness, if compared with the epoxy ones. With regard to artificial aging, the experiments showed that aging has a different impact on different types of adhesives; in particular a slight effect on the mechanical performances or sensitive reduction of the load carrying capacity and of the joint elongation are observed. In general the continuous condensation produces the worst effects on the specimens, while better results were observed after the UV radiations, even though the beneficial effect of the UV rays, which improve the mechanical behavior of the joint for a further polymerization of the adhesive, are impeded by the UV absorbance film.
       
  • Effect of temperature on the probability and cost analysis of mixed-mode
           fatigue crack propagation in patched aluminium plate
    • Abstract: Publication date: Available online 22 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): N. Deghoul, Errouane H., Z. Sereir, A. Chateauneuf, S. Amziane By the present paper, a numerical model for cost and probability analysis of mixed mode fatigue crack propagation in a patched 2024-T3Aluminium plate is developed. The finite element method is used to analyse the temperature effect on the bonded composite repair performance of the Aluminium plate. Using a fine mesh, mid-plane finite element results are in good experimental results given by literature. Different patch shapes are proposed like; circle, rectangle, square, ellipse, regular octagon, and prolonged octagon. The stress intensity factors at the crack tip are chosen as fracture criteria in order to estimate the repair performance. According to the temperature variation, the lifespan of the repaired fatigue crack growth is estimated using Paris law. The repair done on a central inclined crack with a single-side composite patch show that, best results are given by prolonged octagon and patch is damaged under at elevated temperature. The life-cycle of the patched Aluminium plate is obtained by Monte Carlo simulation, and the probability of failure is quantified according to various geometrical and mechanical parameters. At elevated temperature, the most dominant input parameters are thicknesses of adhesive and patch. In sensitivity analysis effect of thickness of the adhesive layer reaches 35%.Finally, a code source has been developed and implanted in ANSYS software, to consider the manufacturing process and optimal maintenance costs to prove the performance of patch operation from both safety and economical point of view.
       
  • Dry adhesion study of polyester/melamine clear coats on galvanized steel
    • Abstract: Publication date: Available online 22 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): T. Greunz, C. Lowe, M. Schmid, G.M. Wallner, B. Strauß, D. Stifter The dry adhesion strength of polyester/melamine clear coats varying in their branching degrees were applied on galvanized steel panels and investigated by pull-off and T-bend testing. It was found that pull-off tensile adhesion is mainly dominated by the type of coating and less influenced by the pretreatment of the substrate. In contrast, the critical T-bend strain is mainly affected by the surface treatment of the galvanized layer with higher stiffness but lower ductility compared to the clear coat. Pull-off tensile strength at room temperature is correlating with the glass transition temperature Tg and a strong viscoelastic contribution is ascribed to the work of adhesion. Samples with adhesive as well as cohesive failure modes were further investigated by X-ray photoelectron spectroscopy (XPS) to determine the interfacial chemistry. Angle-resolved XPS data suggest that the nitrogen from the melamine crosslinker plays a decisive role for the adhesion of the coatings. Regarding the melamine distribution a micro- and a nanostructural effect has to be considered: while maximum melamine concentrations over coating depth are usually found in the bulk region of these clear coats, this work proposes that the remaining melamine at the interface segregates towards the metallic substrate.
       
  • Comparison of J-integral methods to experimentally determine cohesive laws
           in shear for adhesives
    • Abstract: Publication date: Available online 22 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Anders Biel, Ulf StighAbstractHigh-quality simulation methods demand accurate material models. In simulations an adhesive can be represented by a cohesive layer. A cohesive layer model utilizes a cohesive law to represent the homogenized mechanical behaviour of a layer with a thickness. In the current paper we use three experimental methods to measure the cohesive law in shear using the ENF-specimen; one of the methods is novel and is also useful for evaluation of experiments with the ELS-specimen. Two sets of experiments are performed, one with elastic substrates and one with plastically deforming substrates. Each experiment is evaluated using all three methods. The evaluation shows that all methods provide reasonable data; the results are similar if the substrates are elastic. With smaller specimens, the substrates deform plastically and one of the methods is identified as the most accurate.
       
  • Decorated wood fiber/high density polyethylene composites with
           thermoplastic film as adhesives
    • Abstract: Publication date: Available online 22 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Yinan Liu, Xuemin Li, Weihong Wang, Yanan Sun, Haigang Wang It is difficult for wood fibers/high density polyethylene (WF/HDPE) composites to laminate with poplar (Populus tomentosa) wood veneer due to its nonpolar and imporous surface. In present study, four types of thermoplastic films, include two sorts of chlorinated polypropylene (CPP32 and CPP22) film and a mixture film of maleic anhydride grafted polyethylene (MAPE) and HDPE, were developed to glue poplar wood veneer onto WF/HDPE composite board under heat-pressing. The intermediate layer has well water resistance when used aforementioned films. Optical microscopy and scanning electron microscopy (SEM) results show that CPP32 with higher melt flow rate had the higher permeability into poplar wood and fitness with WF/HDPE surface than CPP22; accordingly, the bonding strength of CPP32 was higher than CPP22. MAPE/HDPE film formed the strongest bonding layer for the high compatibility with the WF/HDPE surface which confirmed using SEM, and the covalent bonding between the poplar veneer and MAPE were confirmed using fourier transform infrared (FTIR). Compared to the high heat-press temperature of MAPE/HDPE, CPP32 has the lower processing temperature and acceptable bonding strength. CPP32 and MAPE/HDPE film both suited as the bonding intermediary to substitute traditional adhesive to manufacture veneered wood-plastic composite boards.
       
  • GFRP-To-Timber Bonded Joints: Adhesive Selection
    • Abstract: Publication date: Available online 22 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Chuang Miao, Dilum Fernando, Michael T. Heitzmann, Henri Bailleres Recent research at the University of Queensland (UQ) has led to the development of a new type of structures called “Hybrid Fiber Reinforced Polymer (FRP)-Timber structures” (“HFT”). In HFT structures, FRP is combined with timber veneers to create high-performance, lightweight, easy-to-construct structural members. These HFT members take advantage (i) of the orthotropic properties of both, timber and FRP to orientate the fiber direction to produce optimal composite properties, and (ii) of the geometry of the cross sections to maximize the load bearing capacity for a given amount of material. While preliminary experimental work has revealed as such the effectiveness of HFT structural members, no work has been carried out so far to investigate the behavior of these HFT structures. Performance of these new HFT members relies significantly on the bond between FRP and timber. This paper presents the results of an experimental study aimed at selecting a suitable commercially available adhesive for glass fiber reinforced polymer (GFRP)-to-timber bonded joints. The experimental program included 393 single lap joint tests covering four different commercially available adhesives, two different curing temperatures, and two test methods (dry and moisture cycle tests). The test results revealed that both, polyurethane (PUR) and cross-linking polyvinyl acetate emulsion (PVAx) performed as the best under dry conditions, while PUR was shown to be superior to all other adhesives when subjected to moisture cycles. Epoxy and phenol resorcinol formaldehyde adhesive (PRF) commonly used in FRP structures and laminated timber structures, resp., were found to be less performing structural adhesives for HFT structures.
       
  • ssTannin-based adhesive cross-linked by furfuryl alcohol-glyoxal and epoxy
           resins
    • Abstract: Publication date: Available online 21 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Jun Zhang, Xuedong Xi, Jiankun Liang, Antonio Pizzi, Guanben Du, Shuduan Deng To prepare a natural tannin-based adhesive with good water resistance, an environment friendly furfuryl alcohol-glyoxal resin (FG) synthesized in the laboratory was developed as a cross-linker for tannin-based adhesives. 13C Nuclear Magnetic Resonance (NMR) and Matrix-Assisted Laser Desorption-Ionization Time-of-Flight (MALDI-TOF) mass spectroscopy results indicated that furfuryl alcohol and glyoxal reacted under acidic conditions and that the -CH-(OH)- groups could be shown to be the ones involved in the cross-linking of the tannin-furfuryl-glyoxal adhesive (TFG). The results for the wet shear strength of TFG-bonded plywood showed that the cured TFG was improved and better than that bonded with a tannin-furfuryl alcohol (TF) adhesive. Moreover, the TFG adhesive cross-linked with 12% epoxy resin (EPR) presented a good water resistance. It had a modulus of elasticity (MOE) higher than that of tannin-furfuryl alcohol-formaldehyde (TFF), TF and phenol-formaldehyde (PF) adhesives.
       
  • Effect of surface cold ablation on shear strength of CFRP adhesively
           bonded joint after UV laser treatment
    • Abstract: Publication date: Available online 21 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Xiaohong Zhan, Shuai Chen, Yun Li, Hongen Wang, Yang Yang Ultraviolet(UV) laser treatment on the surface of the carbon fiber reinforced polymer (CFRP) laminate becomes an effective method to benefit the bonding strength of adhesively bonded joint in aerospace industries. In the present research, homomorphic CFRP laminates with different resin distribution on the surface are bonded into single-lap joints. Their shear strengths are tested to evaluate the effect of surface resin distribution on bonding mechanical performance. The different resin distributions on the surface of CFRP laminate are obtained by UV pulse laser with different laser scanning speeds. The scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are conducted to analyze the laser treated surfaces and fracture surfaces of tested joints. The experimental results indicate that the residual resin of CFRP surface increases with the increase of scanning speed. Compared with both the reference surface without laser pre-treatment and that with no-residual resin for bonding, the surface with partial residual resin results in an enhancement of the shear strength of bonded joint. Moreover, the shear strength of the reference sample is higher than that bonded by the surface with no-residual resin. The research lays foundation for understanding the relationship between surface resin distribution and bonding strength.
       
  • The influence of hygrothermal ageing on creep behavior of nanocomposite
           adhesive joints containing multi-walled carbon nanotubes and graphene
           oxide nanoplatelets
    • Abstract: Publication date: Available online 20 May 2019Source: International Journal of Adhesion and AdhesivesAuthor(s): Roya Sadat Ashofteh, Hadi Khoramishad The effect of hygrothermal ageing on the creep behavior of multi-walled carbon nanotube (MWCNT) and graphene oxide nanoplatelet (GONP)-reinforced adhesive joints was investigated. The neat, MWCNT and GONP-reinforced adhesive single lap joints were manufactured and immersed in hot deionized water with three different temperatures for 24 hours and then tested under creep loading. The results showed that the elastic and creep shear strain values of the neat adhesive joints increased by 14% and 25%, respectively, when the water temperature was increased from 30 to 50°C. It was found out that 0.1 wt% MWCNTs had the maximum reinforcing effect against the creep behavior of adhesive joints pre-aged in hot water by 56% and 33% reductions in the elastic and creep strain values of the nanocomposite adhesive joints compared to the neat adhesive joints. Whereas, GONPs caused the maximum reductions of 45% and 20% in the elastic and creep strains of the nanocomposite adhesive joints compared to the neat joints. Furthermore, the Burgers rheological model was employed for simulating the creep response of adhesive joints. Semi-empirical models were proposed for the elastic and creep strains and the Burgers model parameters as functions of the water temperature and MWCNT/GONP weight percentage using the response surface methodology.
       
 
 
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