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  Subjects -> ENGINEERING (Total: 2269 journals)
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ENGINEERING (1201 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 19)
AAPG Bulletin     Full-text available via subscription   (Followers: 5)
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Active and Passive Electronic Components     Open Access   (Followers: 7)
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Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
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at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
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Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 3)
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Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 3)
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Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
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Biotechnology Progress     Hybrid Journal   (Followers: 40)
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Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
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Canadian Geotechnical Journal     Full-text available via subscription   (Followers: 14)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 40)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 7)
Case Studies in Thermal Engineering     Open Access   (Followers: 4)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 3)
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Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 5)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 4)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 1)
CienciaUAT     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 10)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 13)
City, Culture and Society     Hybrid Journal   (Followers: 20)
Clay Minerals     Full-text available via subscription   (Followers: 8)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
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Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
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Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
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Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 23)
Composite Interfaces     Hybrid Journal   (Followers: 5)
Composite Structures     Hybrid Journal   (Followers: 242)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 175)
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Composites Science and Technology     Hybrid Journal   (Followers: 159)
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        1 2 3 4 5 6 7 | Last

Journal Cover Composite Structures
  [SJR: 2.408]   [H-I: 92]   [242 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0263-8223
   Published by Elsevier Homepage  [3041 journals]
  • Effects of external patch configuration on repaired composite laminates
           subjected to multi-impacts
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): S.R.M. Coelho, P.N.B. Reis, J.A.M. Ferreira, A.M. Pereira
      This work intends to study the impact performance of repaired composites by the overlap patch technique and, for this purpose, experimental tests were carried out on single and double-patch specimens. In order to evaluate the impact fatigue strength, both configurations were submitted to multi-impacts, until the full perforation occurs. It was possible to conclude that the double-patch geometry supports higher maximum loads, lower displacements and promotes higher elastic energies. Relatively to the impact energy of 6J, for example, the maximum load and the elastic energy is 97.1% and 51.2% higher, respectively, but the maximum displacement is about 50% lower than the values obtained with the single-patch geometry. Higher impact fatigue life was also observed, as consequence of its higher stiffness. The impact bending stiffness confirms the difference of stiffness between them, and shows to be a parameter able to monitor the damage progression.

      PubDate: 2017-03-03T11:38:39Z
       
  • A novel approach for free vibration of axially functionally graded beams
           with non-uniform cross-section based on Chebyshev polynomials theory
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Yang Zhao, Yixin Huang, Mingquan Guo
      A new approach based on Chebyshev polynomials theory is introduced to analyze free vibration of axially functionally graded Euler–Bernoulli and Timoshenko beams with non-uniform cross-sections. By using high-order Chebyshev expansions to approximate deflections of a beam, its potential energy and kinetic energy, both of which can be considered as weighted inner products of functions, can be expressed in matrix form. All variable geometric and material properties, such as cross-sectional area, area moment of inertia, mass density, Young’s modulus, and shear modulus, are treated as weight functions. In this way, the discrete governing equation can be obtained directly by applying Lagrange’s equation. Natural frequencies and mode shapes can be easily determined by solving the eigenvalue equation. Several numerical examples are carried out to verify the competency of the proposed method. All results are seen to be in excellent agreement with those presented in literature. The overall convergence is approximately exponential, and a highly accurate solution can be gained by using a small number of polynomials.

      PubDate: 2017-03-03T11:38:39Z
       
  • Effects of aging on water and lubricating oil on the creep behavior of a
           GFRP matrix composite
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): L.R. de Souza, A.T. Marques, J.R.M. d'Almeida
      The creep behavior of an E-glass-polyester matrix composite was evaluated as a function of time of immersion in water and lubricant oil. The effect of the test temperature was also evaluated. It was observed that, after 6 and 14months of exposure to the aging fluids, the Young’s modulus of the composite was reduced by 20% regardless the aging fluid when the test was performed at room temperature. For the tests performed at 60°C, the effects of immersion in lubricant oil were more severe than those after immersion in water. Variation of the creep behavior due to exposure to water was associated only to physical aging, because the properties’ variation was correlated to the amount of absorbed water, decreasing only while the amount of water increased. The test temperature was shown to be the main parameter influencing the creep behavior of the composite. The action of the plasticizing effect of water and reduction of oil viscosity with temperature influenced the results of the steady creep rate when the tests were performed at 60°C. Micromechanics approach was used to qualitatively explain the experimental results obtained.

      PubDate: 2017-03-03T11:38:39Z
       
  • Effect of beam orientation on the static behaviour of phenolic core
           sandwich composites with different shear span-to-depth ratios
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Wahid Ferdous, Allan Manalo, Thiru Aravinthan
      This study thoroughly investigated the flexural behaviour of phenolic cored sandwich beams with glass fibre composite skins in the horizontal and vertical positions. The beams have a shear span-to-depth ratio (a/d) varying between 0.5 and 12, and tested under 4-point static bending. Their failure load are then predicted theoretically. The results showed that changing the beam orientation from horizontal to vertical changes the failure mode from brittle to progressive. The sandwich beam’s high bending stiffness can be efficiently utilised by placing them vertically. The a/d ratio played a major role on the load capacity and failure mode. In both orientations, the load capacity decreased with the increased of a/d. The beam failed in shear, a combined shear and bending, and bending for a/d≤2, 2<a/d<6, and a/d≥6, respectively. These failure mechanisms can be correlated to the shear-to-bending stress ratio while the failure load can be reasonably predicted using the available theoretical models. The two-way analysis of variance showed that the beam orientation is a more influential parameter than the a/d ratio. From this study, the horizontal beams are preferable for flexural dominated structures while the vertical beams are desirable for shear dominated structures.

      PubDate: 2017-03-03T11:38:39Z
       
  • High velocity impact behaviour of hybrid basalt-carbon/epoxy composites
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): J. Tirillò, L. Ferrante, F. Sarasini, L. Lampani, E. Barbero, S. Sánchez-Sáez, T. Valente, P. Gaudenzi
      The aim of this work is to investigate the effect of basalt fibre hybridization on carbon/epoxy laminates when subjected to high velocity impacts. In this regard, interply hybrid specimens with four different stacking sequences (sandwich-like and intercalated structures) are tested and compared to non-hybrid reference laminates made of either only carbon or only basalt layers. The response to high velocity impact tests is assessed through the evaluation of the impact and residual velocities of the projectile and the ballistic limit, calculated using experimental data, is compared with the results given by an analytical model, showing a good agreement. The damage in composite laminates is investigated by destructive (optical microscopy) and non-destructive (ultrasonic phased array) techniques. As a result of basalt hybridization, the ballistic limits of all sandwich configurations are enhanced if compared to those of carbon laminates. Therefore the observed decrease of static mechanical properties of hybrid composites is largely compensated by improved response to impact. Advantages also come in terms of cost saving, since the basalt fibre is far less expensive than the carbon one.

      PubDate: 2017-03-03T11:38:39Z
       
  • Multiscale modelling of graphene platelets-based nanocomposite materials
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Wiyao Leleng Azoti, Ahmed Elmarakbi
      This work presents a multiscale framework for the elasto-plastic response of platelets-like inclusions reinforced nanocomposite materials. The solution of the heterogeneous material problem is solved by a kinematic integral equation. An imperfect interface is introduced between the particles and the matrix through a linear spring model LSM, leading to a modified Eshelby’s tensor. The interfacial contribution, related to the strain concentration tensor within each material phase and inside the average strain field, is described by a modified Mori–Tanaka scheme. The non-linear response is established in the framework of the J 2 flow rule. An expression of the algorithmic tangent operator for each phase is obtained and used as an uniform modulus for homogenisation purpose. Numerical results are conducted on graphene platelets GPL-reinforced polymer PA6 composite for several design parameters such as GPL volume fraction, aspect ratio and the interfacial compliance. These results clearly highlight the impact of the aspect ratio as well as the volume fraction by a softening in the overall response when imperfection is considered at the interface. Finally, a multiscale simulation is performed on a three bending specimen showing the capability of the developed constitutive equations to be implemented in a finite element FE code.

      PubDate: 2017-03-03T11:38:39Z
       
  • Low-velocity impact response of composite sandwich structures: Modelling
           and experiment
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Yuan Chen, Shujuan Hou, Kunkun Fu, Xu Han, Lin Ye
      To predict the damage behaviours of composite sandwich structures with a honeycomb core subjected to low-velocity perforation impact, a numerical model was developed addressing the intra-laminar damage, inter-laminar and adhesive delamination and strain rate effect of the materials. In addition, low-velocity perforation impact was conducted on a carbon fibre epoxy composite sandwich panel with a honeycomb core, and scanning electron microscopy was utilized to assess the damage, in an attempt to validate the simulations from the numerical model. The numerical model can describe the key perforation mechanisms and associated damage patterns, with good predictions on the total energy absorption and the impact force-displacement response of the experiments after taking into account the strain rate effects on the materials. The results showed that the total absorbed energy is 10.6J in comparison to 11.5J of the experiment, with an error of −7.8%. Meanwhile, the peak forces are predicted accurately with an error of ∼4.2%.

      PubDate: 2017-03-03T11:38:39Z
       
  • Geometrical and spatial effects on fiber network connectivity
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Alp Karakoç, Eero Hiltunen, Jouni Paltakari
      For fibrous materials such as nonwoven fabrics, paper and paperboards, inter-fiber bonds play a critical role by holding fibers, thus providing internal cohesion. Being a physical phenomenon, inter-fiber bonds occur at every fiber crossing and can be also geometrically detected. In relation to the idea, a statistical geometrical model was developed to investigate the effects of fiber geometry, (i.e. length and cross-sectional properties), spatial distribution, (i.e. location and orientation), and specimen size on fiber network connectivity, which refers to inter-fiber bonds at fiber crossings. In order to generate the fiber network, a geometrical fiber deposition technique was coded in Mathematica technical computing software, which is based on the planar projections and intersections of fibers and provided as supplementary material to the present article. According to this technique, fiber geometries in discrete rectangular prismatic segments were generated by using uniform distributions of the geometrical and spatial parameters and projected onto the transverse plane. Then, projected geometries were trimmed within the transverse boundaries of the specified specimen shape, rectangular prism in this particular study. After this step, fiber crossings were determined through a search algorithm, which was also used as the basis for the fiber spatial regeneration. Thereafter, fibers were accumulated on top of each other by taking fiber crossings into account and eventually fiber networks based on selected properties were formed. By means of the proposed technique, a series of simulation experiments were conducted on paper fiber networks to investigate the correlation between the fiber network connectivity and fiber length, cross-sectional properties, orientation and specimen length, width and thickness.

      PubDate: 2017-03-03T11:38:39Z
       
  • Transverse impact performance and finite element analysis of three
           dimensional braided composite tubes with different braiding layers
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Haili Zhou, Dongmei Hu, Bohong Gu, Baozhong Sun
      The transverse impact performance of three dimensional (3-D) braided composite tubes has been studied both experimentally and numerically. Three types of braided composite tubes were manufactured by changing the number of braiding layers. The transverse impact test was performed on a modified split Hopkinson pressure bar (SHPB) apparatus under three impact gas pressures. From the tests, impact load, displacement and energy absorbed all increase with the increase of gas pressure. The increase of braiding layers leads to the increase of the impact load and energy absorption, but leads to the decrease of impact displacement. The specific load normalized by the linear density of the tubes also increases with the increment of braiding layers. The results indicated that more braiding layers contributed to higher stiffness. The impact damage modes were matrix crack, fiber breakage and shear bands at the area of impact. From the finite element method (FEM), the stress distribution on the impacted tube was highlighted plus the damage progression during the transverse impact cycles.

      PubDate: 2017-03-03T11:38:39Z
       
  • Impact behaviour of pultruded GFRP composites under low-velocity impact
           loading
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Zongjun Li, Amar Khennane, Paul Jonathan Hazell, Andrew David Brown
      This study reports on the results of an experimental investigation on the impact behaviour of pultruded composites samples subjected to low-velocity impacts with higher impact energies ranging from 16.75 to 67J. The specimens were placed and supported according to the requirement of ASTM 7136 standard. The results of impact characteristics and performance are demonstrated and compared for different impact energy levels. The damage evaluation is also introduced to compare the failure modes of pultruded composites subjected to different energy levels. The development and propagation of stress during the low-velocity impacts are analysed using the finite element method. The numerical predictions were found to corroborate the experimental results in terms of load-time and central deflection-time curves.

      PubDate: 2017-03-03T11:38:39Z
       
  • Two-dimensional Chebyshev pseudo spectral modal curvature and its
           application in damage detection for composite plates
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Zhi-Bo Yang, Maciej Radzienski, Pawel Kudela, Wieslaw Ostachowicz
      To overcome the unstable problem in the classical modal curvature method, the two-dimensional Fourier spectral modal curvature method has been proposed in the former work of authors. The existences of the wrap-around effect and the Gibbs phenomenon in the Fourier spectrum-based method, however, necessitate the use of periodic extensions, which affects the efficiency of the modal curvature algorithm. To address the above problems, the two-dimensional Chebyshev pseudo spectral modal curvature is proposed in this work. The presented method inherits the spatial filtering capability and the spectral accuracy of the Fourier spectral modal curvature, and features an efficient modal curvature algorithm in absence of the periodic extension. Numerical and experimental validations are performed on composite structures. Validations show that the proposed method is accurate and effective in the damage detection for the two-dimensional composite structures.

      PubDate: 2017-03-03T11:38:39Z
       
  • Mesh objective implementation of a fibre kinking model for damage growth
           with friction
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Sérgio Costa, Renaud Gutkin, Robin Olsson
      A newly developed physically based model for the longitudinal response of laminated fibre-reinforced composites during compressive damage growth is implemented in a Finite Element (FE) software. It is a mesoscale model able to capture the physics of kink-band formation by shear instability, the influence of the matrix in supporting the fibres and the rotation of the fibres during compression, resulting in more abrupt failure for smaller misalignments. The fibre kinking response is obtained by solving simultaneously for stress equilibrium and strain compatibility in an FE framework. Strain softening creates pathological sensitivity when the mesh is refined. To make the model mesh objective, a methodology based on scaling the strain with the kink-band width is developed. The FE implementation of the current model is detailed with focus on mesh objectivity, and generalized to irregular meshes. The results show that the current model can be used to predict the whole kinking response in a 3D framework and thus account for the correct energy dissipation.

      PubDate: 2017-03-03T11:38:39Z
       
  • Numerical fatigue analysis of CFRP components
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): I. Koch, M. Zscheyge, K. Tittmann, M. Gude
      For the design and successive application of carbon fibre reinforced polymer (CFRP) components in automotive as well as general machine building applications the fatigue degradation behaviour has to be described and modelled realistically. For this purpose a phenomenological fatigue damage modelling and parameter identification strategy for fibre reinforced composites under multi-axial fatigue loads is revised here shortly. Later the method of implementation of the continuum damage mechanics (CDM) approach into finite element software Abaqus© and its validation is described in detail. The presented method is further on used for the FE-based prediction and visualisation of the degradation behaviour of a layered CFRP tension strut under tension-tension fatigue loading. The modelling results are validated with the three dimensional deformation behaviour, the stiffness degradation as well as the damage evolution of the component.

      PubDate: 2017-03-03T11:38:39Z
       
  • Tensile properties of a novel fibre reinforced geopolymer composite with
           enhanced strain hardening characteristics
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Mohammed Haloob Al-Majidi, Andreas Lampropoulos, Andrew B. Cundy
      Strain hardening cementitious concrete is a type of fibre reinforced concrete with enhanced mechanical properties, including strain hardening and ductility. Geopolymer (cement-free) materials represent promising more sustainable alternatives to ordinary Portland cement. Heat treatment however is crucial when using geopolymer materials, to provide comparable mechanical properties to conventional concrete, and there are a number of practical limitations in the application of heat curing in large-scale structures. The main aim of this study is to develop and evaluate the mechanical properties of a novel, sustainable strain hardening fibre-reinforced geopolymer composite material, cured under ambient temperature and thus suitable for cast-in-place applications. In particular, the effect of incorporation of discontinuous fibres on the mechanical performance and on the microstructure of the composite geopolymer materials has been evaluated. Three different types of fibres have been examined in this study (PVA, steel, and glass) with various volume fractions and aspect ratios. The results indicate that room temperature cured, cement-free, strain hardening geopolymer concrete with superior deflection capacity can be produced using a ternary geopolymer binder mix reinforced by 2% PVA fibre or with 2% and 3% of 13mm length steel fibre.

      PubDate: 2017-03-03T11:38:39Z
       
  • Nonlinear thermal buckling of axially functionally graded micro and
           nanobeams
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Navvab Shafiei, Seyed Sajad Mirjavadi, Behzad Mohasel Afshari, Samira Rabby, A.M.S. Hamouda
      In this study, the nonlinear thermal buckling of axially functionally graded (AFG) Euler-Bernoulli micro/nanobeams is analyzed. The Eringen’s nonlocal elasticity theory is used to develop the governing equations of nanobeam and the modified couple stress theory is used to study the microbeam. The micro- and nanobeams are made of pure metal, pure ceramic and axially functionally graded material which is the composition of metal and ceramic. Boundary conditions are considered as clamped (CC) and simply supported (SS). The generalized differential quadrature method (GDQM) is used along with the iteration technique to solve the nonlinear equations. The parametric studies are served to examine the effects of the small scale parameters, length to height ratio (L/h), nonlinear amplitude and AFG power index on the buckling temperature of the micro- and nanobeams.

      PubDate: 2017-03-03T11:38:39Z
       
  • Micromechanics-based thermo-viscoelastic properties prediction of fiber
           reinforced polymers with graded interphases and slightly weakened
           interfaces
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Yan-Ni Rao, Hong-Liang Dai
      A three-dimensional (3D) micromechanical study is performed for effective viscoelastic properties prediction of fiber reinforced polymers (FRPs) containing elastic, transversely isotropic/isotropic ellipsoidal fibers surrounded by graded interphases, embedded in an isotropic, viscoelastic matrix. Based on mean-field homogenization theory, an improved double-inclusion model for FRPs considering graded interphase and imperfect interface is established. Applying two-step homogenization technology, elastic-viscoelastic corresponding approach and Time-Temperature Superposition Principle (TTSP), effective thermo-viscoelastic moduli of FRPs are obtained with respect to the grading and geometric parameters. By solving the interface damage tensors numerically, the mathematical errors in the previously used analytical expressions are avoided, and the entire prediction scheme is extended to fillers at any aspect ratio. Comparing the results for composites with 3D randomly dispersed fibers with existing semi-analytical solutions, the accuracy and efficiency of the proposed method is verified. Parameters analyses are conducted, which indicate that the established model and the proposed method should be of great help for predicting mechanical properties of FRPs and designing micro-composites.

      PubDate: 2017-03-03T11:38:39Z
       
  • The effect of delamination on the critical buckling force of composite
           plates: Experiment and simulation
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Zoltán Juhász, András Szekrényes
      Buckling is one of the main failure type of slender structures, therefore it is important to get know how delaminations affect the critical buckling loads. In this work orthotropic rectangular plates with trough-the-width delamination are modelled using special types of Mindlin plate finite elements. The simulations are verified through experiments. The verification shows that the presented progressive finite element model is able to model the effect of delamination growth on the critical buckling load of uni-axial compressed plates. Possible generalization of the results is also presented.

      PubDate: 2017-03-03T11:38:39Z
       
  • Flume-scale testing of an adaptive pitch marine hydrokinetic turbine
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Ramona B. Barber, Craig S. Hill, Pavel F. Babuska, Richard Wiebe, Alberto Aliseda, Michael R. Motley
      Modern marine hydrokinetic turbine blades are typically constructed from fiber reinforced polymer (FRP) composites, which provide superior strength- and stiffness-to-weight ratios and improved fatigue and corrosion resistance compared to traditional metallic alloys. Furthermore, numerical studies have demonstrated the possibility of tailoring the anisotropic properties of FRP composites to create an adaptive pitch mechanism that can improve system performance, especially in off-design or varying flow conditions. Potential benefits of an adaptive pitch system include increased lifetime energy capture, reduced hydro-elastic instabilities, reduced risk of mechanical failure, and improved efficiency, load shedding, fatigue life, and structural integrity. In this work, static and dynamic testing results for a flume-scale marine hydrokinetic turbine system are presented. Two sets of adaptive composite blades are compared to neutral pitch composite and rigid aluminum designs. Static testing was used to quantify the mechanical load-deformation response of each blade type. Additionally, instantaneous blade and full system loading was measured during dynamic flume testing, allowing a multilevel analysis of adaptive blade performance. Experimental results show notable shifts in the power and thrust coefficients and significant load adjustments induced through passive pitch adaptation, suggesting that adaptive pitch composite blades could be a valuable addition to marine hydrokinetic turbine technology.

      PubDate: 2017-03-03T11:38:39Z
       
  • Nonlinear aeroelastic flutter and dynamic response of composite laminated
           cylindrical shell in supersonic air flow
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Jie Chen, Qiu-Sheng Li
      Aeroelastic flutter characteristics and dynamic response of a composite laminated circular cylindrical shell under combined action of radial harmonic excitation, compressive in-plane force and aerodynamic pressure are studied in this paper. The first-order piston theory is employed to model the aerodynamics pressure. Partial differential equations governing the vibrations of the cylindrical shell are derived based on the Hamilton’s principle and the Donnell’s nonlinear shell theory. The Galerkin’s method is adopted to discretize the partial differential governing equations to a set of nonlinear ordinary differential equations. The four-dimensional averaged equation is obtained by applying the method of multiple scales under the case of 1:2 internal resonance. The critical free stream static pressure originating flutter of the shell is determined by solving the eigenvalue problem. The phase portrait and time history diagrams are presented to demonstrate the character of the limit cycle oscillation of the shell. The influence of different geometrical parameters, such as the radius, length and thickness of the shell, on the flutter characteristics of the composite laminated circular cylindrical shell are discussed in details. The influences of the amplitudes of the in-plane and transverse excitations on the frequency–response curves and force-response curves are also investigated.

      PubDate: 2017-03-03T11:38:39Z
       
  • Bending analyses of FG-CNTRC plates using the modified mesh-free radial
           point interpolation method based on the higher-order shear deformation
           theory
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Vuong Nguyen Van Do, Chin-Hyung Lee
      This study presents nonlinear bending analyses of functionally graded (FG) carbon nanotube-reinforced composite (CNTRC) plates using the modified mesh-free radial point interpolation method (RPIM). The nonlinear bending formulations of the FG-CNTRC plates are derived from the modified RPIM which employs a new radial basis function able to construct the shape functions without the need for introducing supporting fixing coefficients based on the higher-order shear deformation plate theory. Single-walled carbon nanotubes (SWCNTs) are selected as the reinforcement and the effective material properties of the FG-CNTRC plates are evaluated by an equivalent continuum model based on the rule of mixture. The simulated results by the modified RPIM are compared with the other numerical solutions to verify the effectiveness and the accuracy of the developed mesh-free method. Detailed parametric studies are then performed to explore the effects that the plate width-to-thickness ratio, aspect ratio, load type, boundary condition and initial deflection have on the nonlinear flexural responses of the CNTRC plates, and the results for uniformly distributed (UD) CNTRC plate are provided for comparison. Results demonstrate that the modified mesh-free RPIM can effectively predict the nonlinear bending behavior of the CNTRC plates.

      PubDate: 2017-03-03T11:38:39Z
       
  • Multi-objective optimization of laminated composite beam structures using
           NSGA-II algorithm
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): T. Vo-Duy, D. Duong-Gia, V. Ho-Huu, H.C. Vu-Do, T. Nguyen-Thoi
      The paper deals with the multi-objective optimization problems of laminated composite beam structures. The objective function is to minimize the weight of the whole laminated composite beam and maximize the natural frequency. In particular, the simultaneous use of all the design variables such as fiber volume fractions, thickness and fiber orientation angles of layers is conducted, in which the fiber volume fractions are taken as continuous design variables with the constraint on manufacturing process while the thickness and fiber orientation angles are considered as discrete variables. The beam structure is subjected to the constraint in the natural frequency which must be greater than or equal to a predetermined frequency. For free vibration analysis of the structure, the finite element method is used with the two-node Bernoulli-Euler beam element. For solving the multi-objective optimization problem, the nondominated sorting genetic algorithm II (NSGA-II) is employed. The reliability and effectiveness of the proposed approach are demonstrated through three numerical examples by comparing the current results with those of previous studies in the literature.

      PubDate: 2017-03-03T11:38:39Z
       
  • Electrical impedance spectroscopy for measuring the impedance response of
           carbon-fiber-reinforced polymer composite laminates
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Khaled Almuhammadi, Tushar Kanti Bera, Gilles Lubineau
      Techniques that monitor the change in the electrical properties of materials are promising for both non-destructive testing and structural health monitoring of carbon-fiber-reinforced polymers (CFRPs). However, achieving reliable monitoring using these techniques requires an in-depth understanding of the impedance response of these materials when subjected to an alternating electrical excitation, information that is only partially available in the literature. In this work, we investigate the electrical impedance spectroscopy response at various frequencies of laminates chosen to be representative of classical layups employed in composite structures. We clarify the relationship between the frequency of the electrical current, the conductivity of the surface ply and the probing depth for different CFRP configurations for more efficient electrical signal-based inspections. We also investigate the effect of the amplitude of the input signal.

      PubDate: 2017-03-03T11:38:39Z
       
  • Development of an innovative design of a composite-sandwich based vehicle
           roof structure
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Soroosh Borazjani, Giovanni Belingardi
      Obligatory standards are dictated to vehicle manufacturers for decreasing the high number of road dead tolls in rollover crashes; at the same time demands to produce light-weight vehicles have increased substantially to reduce the toxic gases emission. This paper presents a new design of the roof strengthening configuration in which sandwich material has been used. This type of configuration improves the energy-absorption capacity of the vehicle roof system and dissipates impact energy in a controlled manner. In reality, carrying out roof crush test is not cost effective, thus numerical analysis of vehicle roof crush test has been performed according to standard FMVSS 216 test. Sandwich structures with unidirectional carbon/epoxy composite face-sheets and Expanded Polypropylene (EPP) foam core have been used to model different configurations for vehicle roof structure. The effects of increasing the foam core density and face-sheets thickness on the energy absorption and strength-to-weight ratio (SWR) of vehicle roof structure have been investigated. Results revealed that, the optimized sandwich solution type 6 with the face-sheets thickness of 0.8mm and foam core of 70kg/m3 density reduces the vehicle roof panel mass by 68% while it has almost the same structural performance with the steel solution having equal value of SWR.

      PubDate: 2017-03-03T11:38:39Z
       
  • Closed-form solution for thermal, mechanical, and thermo-mechanical
           buckling and post-buckling of SMA composite plates
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Mohammad-Zaman Kabir, Behrang Tavousi Tehrani
      In this paper, an analytical study on thermal, mechanical, and thermomechanical buckling and post-buckling of symmetric laminated composite plates reinforced with shape memory alloy (SMA) fibers are presented. The closed-form solution used in this study is developed based on the FSDT incorporated with the Von-Karman non-linear strains. The effect of SMA fibers is captured by adding a tensile recovery, stress term that determined using 1-D simplified Brinson’s model, in the constitutive equations of the SMA composite plate. Galerkin technique is implemented for solving the nonlinear partial differential equations of motion to obtain buckling load and post-buckling path. The influence of several parameters such as SMA activation temperature, SMA fiber volume fraction, SMA pre-strain, biaxial ratio, etc., are studied in this work. Due to the generation of recovery force, significant improvement in buckling load is attained by increasing each of the SMA fiber volume fraction, activation temperature or SMA pre-strain.

      PubDate: 2017-03-03T11:38:39Z
       
  • In process monitoring of cutting temperature during the drilling of FRP
           laminate
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): L. Sorrentino, S. Turchetta, C. Bellini
      Drilling is the most important machining operation applicable to polymeric composite materials since it is essential for mechanical coupling of parts. Drilling process provokes several issues, including localized thermal shock, caused by the presence of abrasive and extremely hard fibres and the low thermal conductivity of composite, which restricts the heat dissipation. Such dangerous issue can be evaluated by examining the process temperature, whose value depends on cutting parameters. Therefore, monitoring of process temperature is indispensable to obtain useful information for machining optimization. In this work the influence of cutting parameters was analysed, measuring the temperature during drilling on tool and in the laminate for both CFRP and GFRP. Temperature trends as a function of cutting speed and feed rate were obtained and dangerous values of cutting parameters were identified. Finally, a preliminary numerical model was developed to simulate the temperature rising in the material during drilling.

      PubDate: 2017-03-03T11:38:39Z
       
  • Modelling damage growth in composites subjected to impact and compression
           after impact
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): M.R. Abir, T.E. Tay, M. Ridha, H.P. Lee
      Compression After Impact (CAI) tests are frequently performed to characterize the effect of impact damage on strength of composites. This paper presents an integrated single finite element model that enables analysis of impact damage and CAI without major simplifications and idealizations of damage in composites. When applied to a series of quasi-isotropic laminates, the results obtained from simulation correlate well with experiment with regards to damage shapes, sizes and CAI strength. Failure during CAI was found to be triggered by local buckling, causing fibre and delamination damage growth (during compression) that leads to rapid and sudden load drop. Compressive strength, Mode I fibre compressive fracture toughness and Mode II interlaminar fracture toughness were found to be the key parameters that affect residual strength of composites. Such models can lead to a better understanding of damage growth mechanisms necessary for development of damage tolerant structures, as well as promote virtual testing, with considerable cost and time savings.

      PubDate: 2017-02-24T01:51:26Z
       
  • Young's modulus estimation for CNT reinforced metallic foams obtained
           using different space holder particles
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): L. Pérez, R. Mercado, I. Alfonso
      In this work Finite Element Analysis (FEA) was used in order to estimate the effect of the pore size and the volume fraction of carbon nanotubes (CNT) used as reinforcement, for Al-12%Si foams with 50% of porosity. Two different space holder particles (SHP) were used to simulate foams manufactured by infiltration, modeling pores of two different fractal distributions according to the size of the SHPs: NaCl and NH4HCO3. Random pore arrangements were modeled combining Discrete Element Method (DEM) and FEA. Coordinates were firstly generated using DEM, while in a second stage CNTs and pores were modeled by FEA. Estimations show important differences according to the used SHP, decreasing the Young's modulus for the foams with the smallest pore sizes. The Young's modulus also increased with the CNT volume fraction. Results showed the importance of the selection of random models and the use of FEA for predicting the Young's modulus of reinforced metallic foams.

      PubDate: 2017-02-24T01:51:26Z
       
  • Effect of distance between impact point and hole position on the impact
           fatigue strength of composite laminates
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): R.A.M. Santos, P.N.B. Reis, M.J. Santos, C.A.C.P. Coelho
      An impact fatigue study was performed to evaluate the effect of the distance between the impact point and the hole on the fatigue life of glass fibre/epoxy laminates. For this purpose, experimental tests were carried out in square plates and for the distances of 0, 5, 10 and 20mm, from the impact point. The results were compared with the ones obtained in plates without hole. It was possible to conclude that the fatigue life decreased, comparatively to the control samples, about 10.9%, 40%, 63.6% and 69.1% for the distances of 20mm, 10mm, 5mm and 0mm, respectively. Higher distances promote higher maximum loads and elastic restitution, but an opposite trend in terms of maximum displacement. For example, it was found for 20mm a maximum load around 5.54kN, a displacement of about 4.4mm and an elastic energy of 59.2%, while for 0mm these values were about 4.59kN, 5.7mm and 40.4%, respectively. In terms of multi-impacts, the damage severity is also very influenced by the distance. For small distances the damage progresses quickly, while three stages can be found for the control samples and for the distance of 20mm.

      PubDate: 2017-02-24T01:51:26Z
       
  • Fatigue reliability design of composite leaf springs based on ply scheme
           optimization
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Chen Qian, Wenku Shi, Zhiyong Chen, Shixiang Yang, Qianqian Song
      The study of composite leaf springs has been popular in automotive light weighting. Particularly, the research on the fatigue reliability of composite leaf springs is crucial. This paper proposed the fatigue law inference of the parabolic composite leaf spring, which was validated by fatigue bench tests. On the bases of the ply scheme design method and the sandwich unit concept, the non-continuous layer section and the stacking order were presented. The stacking sequence was optimized using Genetic Algorithm. The production of composite leaf spring samples, on which the fatigue bench test was conducted, was based on the optimized ply scheme. Results indicate that the fatigue life of composite leaf springs can be improved by using the proposed ply scheme design method.

      PubDate: 2017-02-24T01:51:26Z
       
  • Formability of complex composite structures with ribs made of long
           carbon-fiber-reinforced prepregs
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Ji-Hun Bae, Min-Gu Han, Seung-Hwan Chang
      A long fiber prepreg sheet (LFPS) composed of long carbon fibers with lengths of 50mm and a fast-curing epoxy resin was used to fabricate complex-shaped structures with ribs using thermal compression molding. The formability of the composite structures was evaluated for various compression pressures (10, 30, and 60MPa) and times (5 and 10min) at a fixed curing temperature (155°C). Using a single layer of LFPS, the highest geometric accuracy of the composite structure with ribs was 99.64%, and the highest average fiber volume fraction of the rib part was 29.82% under 30MPa for 10min. Furthermore, the highest flexural strength and modulus of the ribs were 253MPa and 18GPa, respectively, under the condition of 30MPa and 10min. These values increased to 366MPa and 26GPa, respectively, when two layers (a fiber volume fraction of 38.15%) were applied. Among the various thermoforming conditions, an applied pressure of 30MPa and a pressing time of 10min at 155°C were the most appropriate to achieve relatively excellent net-shape molding with improved mechanical properties.

      PubDate: 2017-02-24T01:51:26Z
       
  • High strain rate response of nanofiber interlayered structural composites
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Elif Özden-Yenigün, Kaan Bilge, Emin Sünbüloğlu, Ergun Bozdağ, Melih Papila
      Nanofibrous interlayer toughening strategy for laminated composite materials typically demonstrated at quasi-static loading is here evaluated under high strain rate deformation. Carbon fiber reinforced composite laminates of (0/90)25s stacking sequence are interlayered by polystyrene-co-glycidyl methacrylate (P(St-co-GMA)) nanofibers which are chemically tuned for interfacial compatibility when embedded in epoxy matrix. The cubical composite specimens are cut and subjected to high strain-rate deformation via Split Hopkinson pressure bar testing. Specimens are hit at their through-the-thickness (stacking) and side-to-side (in-plane) directions. The change in the dissipation of energy due to altered interlaminar microstructure is monitored and reported. Enhancement in the capacity of the energy dissipation due to the nanofibrous interlayers is as high as 80% in-plane and 40% through thickness directions, depending on the strain rate. The results overall suggest that interlayer toughening strategy used in this work prevents the formation of critical matrix cracks that can cause the formation of instantaneous mode II delamination. Incorporation of the nanofibers without causing notable weight penalty effectively toughen the matrix dominant interlaminar zones under high strain rate conditions as well.

      PubDate: 2017-02-24T01:51:26Z
       
  • Modelling the orthogonal cutting of UD-CFRP composites: Development of a
           novel cohesive zone model
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Alessandro Abena, Sein Leung Soo, Khamis Essa
      The inhomogeneous and anisotropic nature of CFRP presents a challenge achieving accurate simulations largely due to limitations of current material constitutive relationship, in particular for predicting debonding of the matrix and fibre. Following a comprehensive review of the various published cohesive models a new approach for representing the fibre–matrix interface is proposed for a three-dimensional FE model of orthogonal cutting of UD-CFRP. While severe deformations of the cohesive elements are generally observed when surrounding elements fail, excessively strong bonds are typically formed when employing surface-based cohesive behaviour. The proposed approach overcomes these limitations by employing zero thickness cohesive elements based on a traction–separation law, which are deleted from the analysis if any of the surrounding elements fails. The FE models were validated in terms of predicted cutting and thrust forces against published data for different fibre orientations. Cutting forces showed good agreement to experimental results for 90° and 135° (error within 5%), while thrust forces are generally underestimated.

      PubDate: 2017-02-24T01:51:26Z
       
  • Non-classical vibration behavior of highly anisotropic corrugated
           laminates
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): C. Thurnherr, T. Pedergnana, G. Kress, P. Ermanni
      This paper presents a detailed investigation about the vibration behavior of corrugated laminates. In highly anisotropic corrugated laminates different non-classical vibration modes were observed and are reported in this work. Apart from in-plane modes, we show in particular shear rotational modes which occur due to the high anisotropy, the distribution of mass, and the influence of the shear compliance. The work contains a detailed FEM study, a comparison with an equivalent plate model and an analytical model and examines the limitations of the latter two. It points out for which geometry and material parameters the well known and often used homogenized plate models are applicable. Parametric studies are conducted investigating the influence of the corrugation amplitude, the aspect ratio, the anisotropy of the material, and boundary conditions on the vibration behavior. The found results can be used for the design of highly anisotropic corrugated laminated plates and the analysis of their vibration behavior.

      PubDate: 2017-02-24T01:51:26Z
       
  • Fracture and impact characterization of novel auxetic Kevlar®/Epoxy
           laminated composites
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Sen Yang, Vijaya B. Chalivendra, Yong K. Kim
      Experimental study was performed to investigate fracture and impact properties of novel Auxetic Kevlar® laminated composites. For comparison, standard Kevlar® woven composites with and without polyurethane treatment were also considered in this study. For these three composites, short nylon fibers of two different fiber lengths and three different fiber densities were flocked between laminates. Vacuum infusion process along with optimized compaction was employed to fabricate composites. The double cantilever beam configuration was used to investigate the fracture properties. The Auxetic Kevlar® composites showed a significant improvement of 225% in fracture toughness compared to regular woven Kevlar® composites. Furthermore, the initiation toughness was increased by 577% with the application of flocking in Auxetic Kevlar®. During impact testing, the Auxetic Kevlar® reinforced composites showed a significant reduction in damaged area compared to woven counterpart. On the other hand, the reduction in damaged area influenced the reduction in impact energy absorption.

      PubDate: 2017-02-24T01:51:26Z
       
  • Prediction of the tensile strength of unidirectional carbon fiber
           composites considering the interfacial shear strength
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Wonjin Na, Geunsung Lee, Minchang Sung, Heung Nam Han, Woong-Ryeol Yu
      The tensile strength of unidirectional (UD) carbon fiber composites was predicted considering the interfacial shear strength (IFSS). First, the effect of the IFSS on the load transfer to the surrounding fibers when a fiber was broken was analyzed using finite element method and then the stress concentration factor (SCF) of each surrounding fiber was determined. The multiple fracture number was calculated using the SCF and a statistical approach that can calculate the probability of fiber breakage propagation due to the stress concentration when the broken fibers exist in neighbor. Finally, the tensile strength of UD carbon fiber composites was predicted using the multiple fracture number and was compared with experimental results, demonstrating the validity of the current method. An optimal IFSS that can ensure the maximum tensile strength of UD carbon fiber composites is discussed based on the calculation results.

      PubDate: 2017-02-24T01:51:26Z
       
  • Bond behaviors of FRP-to-concrete interface under the control of a novel
           end-anchorage system
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Yingwu Zhou, Xilong Chen, Zhiheng Fan, Lili Sui, Dawang Li, Feng Xing
      The externally bonded fiber-reinforced polymer (FRP) is one of the most effective techniques for the strengthening and rehabilitation of deteriorated concrete structures. The debonding of an FRP-concrete interface is the typical failure mode of an FRP-strengthened concrete structure, leading to a very low effective utilization of FRP material and an inductile failure of the structure. In this paper, a novel end-anchorage device was developed and installed at both ends of the FRP to restrict the premature debonding of the FRP. The end-anchorage device has a ductile behavior and by relying on the deformation of the device, the deformability of the strengthened structure and the maximum FRP stress during debonding can be improved to a large extent, thus a significant improvement on the structural load capacity and ductility can be realized. In this study, the adjusting mechanism of the end-anchorage system on the bond behavior of the FRP-concrete interface was systematically investigated. First, the bond behavior of the FRP-concrete interface was experimentally studied using single shear test. Second, the bond strength, bond-slip relation curve, and the strain distribution of the FRP along the bonded area were analyzed. Finally, a prediction model for the interfacial bond strength under the end-anchorage system was proposed. Comparisons with the experimental results indicate that the proposed model can provide a reasonable good accuracy in predictions.

      PubDate: 2017-02-24T01:51:26Z
       
  • Development and application of a numerical procedure for the simulation of
           the “Fibre Bridging” phenomenon in composite structures
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): A. Riccio, A. Russo, A. Sellitto, A. Raimondo
      In this paper, a novel numerical procedure for delamination growth simulation able to evaluate the Fibre Bridging effect has been used to numerically investigate the mechanical behaviour of stiffened composite panels. The proposed methodology, implemented in ANSYS® FEM code by Ansys Parametric Design Language (APDL), allows to take into account the real variation of the Critical Energy Release Rate associated to the Fibre Bridging phenomenon. A first numerical application has been performed for preliminary validation purposes, simulating the flexural behaviour of representative section of a stiffened composite plate. The considerable agreement between the obtained numerical results and the literature experimental data confirms the effectiveness and the accuracy of the proposed model. Finally, a parametric analysis has been carried out in order to study the influence of the geometrical parameters of single stiffened composite panels in terms of skin-stringer debonding including Fibre Bridging.

      PubDate: 2017-02-24T01:51:26Z
       
  • Investigation of failure initiation in curved composite laminates using a
           higher-order beam model
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): C. Thurnherr, R.M.J. Groh, P. Ermanni, P.M. Weaver
      Curved laminates are prone to delamination failure from applied bending moments that straighten out the laminate and induce tensile stresses in the unreinforced radial direction. These non-classical through-thickness stresses are important even for thinner configurations and need to be accounted for in the design of lightweight composite structures, preferably in a computationally efficient manner. Here, we investigate failure-inducing critical stresses for a number of curved laminates using a higher-order beam model derived from the Hellinger–Reissner mixed variational principle, which guarantees that the hoop, interlaminar shear and radial stresses are equilibrated. By solving the governing equations of the theory in the strong form using the pseudo-spectral differential quadrature method, the model is capable of predicting accurate 3D stress fields in curved laminates, even in the vicinity of localised features such as supported edges. The model is used alongside commonly used failure criteria to reproduce experimental failure initiation results found in the literature, and the comparison suggests that failure mode, location and load are all predicted accurately. Finally, failure maps that highlight the critical stress component for failure initiation are constructed. As the thickness of the curved laminate increases, the critical stress component transitions from intralaminar hoop stress to interlaminar shear or radial stress depending on the specific laminate configuration. These findings and failure maps collectively provide insights into the mechanics of failure initiation that should also prove useful for design purposes.

      PubDate: 2017-02-24T01:51:26Z
       
  • Stiffness and failure behaviour of wood based honeycomb sandwich corner
           joints in different climates
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Jerzy Smardzewski, Michał Słonina, Michał Maslej
      Changes in air relative humidity and temperature exert a negative influence on hygroscopic wood based composites from which honeycomb sandwich panels are manufactured. Ready market globalisation causes that furniture from honeycomb sandwich panels manufactured in conditions of a dry climate are utilised in a tropical climate or are transported for several weeks through a tropical climate zone and then used in a dry climate. Water sorption and desorption processes by wood composites affect their loss of stiffness and strength. This study determined the impact of changes in ambient climatic conditions on the stiffness and strength of joints manufactured from honeycomb panels. A new method of numerical stiffness and strength modelling of joints subjected to changes in air relative humidity and temperature was developed.

      PubDate: 2017-02-24T01:51:26Z
       
  • A study of flattening process of deployable composite thin-walled
           lenticular tubes under compression and tension
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Yu Hu, Wujun Chen, Jifeng Gao, Jianhui Hu, Guangqiang Fang, Fujun Peng
      Carbon fiber reinforced polymers (CFRP) laminates are extensively employed to manufacture the deployable composite thin-walled lenticular tubes (CTLTs). This paper presents a comparison of experimental and numerical and analytical results of compressive and tensile flattening types of deployable CTLTs. Firstly, a compressive flattening model created by ABAQUS was introduced to obtain its strain and stress of each ply of composite tube. Secondly, compressive flattening experiments were performed for CTLT specimens to explore compressive flattening mechanism of CTLTs. Then, the numerical simulation methods to simulate the compressive flattening of CTLTs were verified by comparing measurements and corresponding numerical results. Thirdly, analytical models are employed to predict the flattening process of CTLTs under compression. Lastly, for the tensile flattening process of CTLTs, the numerical simulation method and corresponding experiments and theoretical results are respectively also carried out with aim of revealing mechanical properties of CTLTs under tension. The flattening process of CTLTs can be considered to be a nonlinear deformation and small strain process. For the compressive flattening, the maximum compressive force, displacement and strain are 98N, 60mm and 0.29%, respectively. For the identical tensile flattening, the maximum tensile force, displacement and strain are 550N, 42.5mm, 0.53%. respectively. It is found that the compressive flattening way is a better choice in the design of the actuated mechanism.

      PubDate: 2017-02-24T01:51:26Z
       
  • Optimum design of fatigue-resistant composite laminates using hybrid
           algorithm
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): H. Arda Deveci, H. Seçil Artem
      In this study, a fatigue life prediction model termed as Failure Tensor Polynomial in Fatigue (FTPF) is applied to the optimum stacking sequence design of laminated composites under various in-plane cyclic loadings to obtain maximum fatigue life. The validity of the model is investigated with an experimental correlation using the data available in the literature. The correlation study indicates the reliability of FTPF, and its applicability to different composite materials and multidirectional laminates. In the optimization, a hybrid algorithm combining genetic algorithm and generalized pattern search algorithm is used. It is found by test problems that the hybrid algorithm shows superior performance in finding global optima compared to the so far best results in the literature. After the verifications, a number of problems including different design cases are solved, and the optimum designs constituted of discrete fiber angles which give the maximum possible fatigue lives are proposed to discuss. A comparison study is also performed with selected design cases to demonstrate potential advantages of using non-conventional fiber angles in design.

      PubDate: 2017-02-24T01:51:26Z
       
  • Bat-inspired optimization of multilayered adaptive structures
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): D.M.S. Costa, M.A.R. Loja
      Adaptive structures constituted by composites and smart materials is a remarkable engineering combination that join together the already known composites’ advantages and the possibility of actively control the mechanical response of a structure. These versatile structures are able to react and interact with their surrounding environments, continuously, to accomplish specific objectives. In this work, the main objective is to study, model and predict the mechanical behaviour of adaptive structures by programming the finite element method and optimization algorithms based on micro-bats’ echolocation capacity. An integrated symbolic-numerical-graphical package devoted to the analysis of plate/beam-type structures and its meta-heuristic optimization is implemented, with capabilities of simulating active multilayered structures, constituted by a variable number of different material models. Graded mixtures of piezoelectric particles and non-active materials are also modelled along the structures’ length direction. A set of illustrative case studies are performed, for different types of structures and materials and the results obtained are discussed and conclusions are drawn.

      PubDate: 2017-02-24T01:51:26Z
       
  • Influence of concrete strength combined with fiber content in the residual
           flexural strengths of fiber reinforced concrete
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Jong-Han Lee
      Recently, the design and construction of fiber reinforced concrete structures, such as floor slabs and precast tunnel linings, require using the actual values of the residual flexural strength instead of the average concept of the equivalent residual flexural strength ratio. An experimental study was performed to examine the direct residual flexural strengths of steel fiber reinforced concrete beams with various concrete strengths, 25, 35, and 45MPa, and fiber volume factions, 0.25, 0.375, and 0.50%. The influence of the concrete strength and fiber content in the limit of proportionality, residual flexural strength, and energy absorption capacity were evaluated. The fiber reinforced concrete beams with a strength of 45MPa showed a higher increase in the residual flexural strength immediately after concrete cracking, particularly for a fiber volume fraction of 0.5%. On the other hand, as concrete cracking propagated, the residual flexural strength and energy absorption capacity values rapidly decreased in the beams with a concrete strength of 45MPa.

      PubDate: 2017-02-24T01:51:26Z
       
  • Stress redistribution around clusters of broken fibres in a composite
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Luc St-Pierre, Ned J. Martorell, Silvestre T. Pinho
      A key aspect of the longitudinal tensile failure of composites is the stress redistribution that occurs around broken fibres. Work on this topic has focussed mainly on the stress field surrounding a single broken fibre; however, this is an important limitation as unstable failure in carbon fibre bundles occurs when a cluster of about 16 or more broken fibres is formed. Therefore, we have developed a detailed Finite Element (FE) model to investigate how stress redistribution varies with the number of broken fibres in a cluster. The results show that both the recovery length and stress concentration factor increase significantly with increasing number of broken fibres in a cluster. We have also developed an analytical model, suitable to be included in existing or new fibre bundle models, that captures how the recovery length and stress concentration factor vary with the broken cluster size, and validated its predictions against our FE simulations. Finally, we extended our FE model to predict the survival probability of fibre bundles using Monte Carlo simulations, and found that these predictions were in good agreement with experimental and analytical results on microcomposites.

      PubDate: 2017-02-24T01:51:26Z
       
  • Triangular based prismatic finite element for the analysis of orthotropic
           laminated beams, plates and shells
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Rogério Carrazedo, Humberto Breves Coda
      In this paper, we revisit the FEM solution of laminated plates and shells that nowadays are mostly done by low order solid or shell finite elements enriched by stress or strain fields, or by specific kinematics dedicated to the analysis of such structures. We introduce a triangular based prismatic finite element of any approximation order capable of solving from very thin to very thick laminated plates and shells, with the following properties: (i) locking-free behavior; (ii) good stress distribution even for complex materials; (iii) geometrically exact description of large displacements; and (iv) geometry dedicated to evaluate plates and shells (laminated or not) free of problems due to distorted meshes or ill-conditioned systems as thickness decreases. This triangular based prismatic finite element can also be employed in laminated beams, holding the same properties. The proposed element uses total Lagrangian description based on positions, and its performance regarding the claimed properties is demonstrated in several examples.

      PubDate: 2017-02-24T01:51:26Z
       
  • Global dynamics of composite panels with free-layer damping treatment in
           subsonic flow
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Tian-Jun Yu, Sha Zhou, Xiao-Dong Yang, Wei Zhang
      Global dynamics of forcedly excited composite panels with free layer damping treatment in subsonic flow near the first-order critical velocity is investigated. Hamilton’s principle is implemented to derive the PDE of such fluid-structure interaction systems. Then the governing equation is transformed into a discretized nonlinear gyroscopic system via assumed modes and Galerkin’s method. The canonical transformations and normal form theory are applied to reduce the equations of motion to near-integrable Hamiltonian standard forms considering zero to one internal resonance. The Energy-Phase method is employed to demonstrate the existence of chaotic dynamics by identifying the existence of multi-pulse jumping orbits in the perturbed phase space. In both the Hamiltonian and the dissipative perturbation case, the homoclinic trees which describe the repeated bifurcations of multi-pulse solutions are demonstrated. In the case of dissipative perturbation, the existence of generalized Šilnikov’s type of orbits which are homoclinic to fixed points on the slow manifold are examined and the parameter region for which the dynamical system may exhibit chaotic motions in the sense of Smale horseshoes are obtained analytically. The present research illustrates that the existence of multi-pulse homoclinic orbits can provide a mechanism for how energy flow from the high-frequency mode to the low-frequency mode. The global results are finally interpreted in terms of the physical traveling wave motion of such gyroscopic continua.

      PubDate: 2017-02-24T01:51:26Z
       
  • Buckling and post-buckling analysis of the delaminated composite plates
           using the Koiter–Newton method
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Ke Liang, Qin Sun
      The Koiter–Newton method has been proved to be a computationally efficient method for buckling and post-buckling analysis of structures, using a novel reduced-order modeling strategy. In this paper, the existing method is extended for laminated composite plates with delamination. We develop a 4-node quadrilateral element S4DE as a geometric linear element in the co-rotational formulation of the Koiter–Newton method. The assumed layerwise displacement model of the developed element is enriched with Heaviside unit step functions to model delamination. The displacement fields of each layer are described using the superposition of first-order shear deformation and layerwise functions. The zig–zag theory is applied to enhance the numerical accuracy and computational efficiency of the developed element. The construction of the reduced order model requires derivatives of the strain energy with respect to the degrees of freedom up to the fourth order, which is two orders more than traditionally needed for a Newton based nonlinear finite element technique. The geometrical nonlinearities are taken into account using derivatives of the local co-rotational frame with respect to global degrees of freedom. Various laminated plates with different thicknesses, delamination lengths and stacking sequences are considered to validate the good performance of the present method in terms of numerical reliability, accuracy and computational effort.

      PubDate: 2017-02-24T01:51:26Z
       
  • Damage detection in beam-like composite structures via Chebyshev pseudo
           spectral modal curvature
    • Abstract: Publication date: 15 May 2017
      Source:Composite Structures, Volume 168
      Author(s): Zhi-Bo Yang, Maciej Radzienski, Pawel Kudela, Wieslaw Ostachowicz
      This paper presents the Chebyshev pseudo spectral modal curvature formulation for damage detection in beam-like composite structures. The proposed method is the extension of authors' former work which is based on the Fourier spectral method. The Chebyshev pseudo spectral modal curvature overcomes the severe shortcomings of Fourier transform based spectral formulation which has serious problems associated with the wrap-around effect while analyzing the finite length signal. Moreover, the proposed method inherits the spatial filtering capability and spectral accuracy of the Fourier spectrum-based modal curvature, which ensures the robustness of the modal curvature calculation in noisy conditions. The validations of the presented method and comparisons with the Fourier spectrum based method are numerically and experimentally demonstrated for composite structures.

      PubDate: 2017-02-17T03:07:15Z
       
  • Estimation of aramid fiber/epoxy interfacial properties by fiber bundle
           tests and multiscale modeling considering the fiber skin/core structure
    • Abstract: Publication date: 1 May 2017
      Source:Composite Structures, Volume 167
      Author(s): Guocheng Qi, Boming Zhang, Shanyi Du, Yalin Yu
      In this work, the aramid fiber/epoxy interfacial normal bonding property and interfacial shear property were estimated by transverse fiber bundle tensile (TFBT) test and 45° fiber bundle tensile (45FBT) test, respectively. The fracture surfaces of the fiber bundle samples after the mechanical test were observed to investigate the micro failure mechanisms. The interfacial debonding was found coupled with fibrillation of the fiber surface due to the apparent skin/core structure of aramid fibers. Furthermore, the multiscale model based on the generalized methods of cells (GMC) considering the skin/core structure and the fiber/matrix interphase was established to calculate the micro stresses. The interfacial normal strength (IFNS) in the TFBT specimen and interfacial shear strength (IFSS) in the 45FBT specimen were determined by the combination of the experimental and analytical results. Eventually, the effects of skin/core stiffness and thickness on the calculated IFNS and IFSS values were investigated.

      PubDate: 2017-02-11T08:25:03Z
       
 
 
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