Showing papers on "Composite laminates published in 2006"
TL;DR: In this paper, a series of [0/90]3s laminates with varying void contents were fabricated and a characterization of void distribution, size, and shape within the Laminates was obtained using ultrasonic c-scan and optical metallography techniques.
387 citations
TL;DR: In this paper, a methodology to predict the onset of damage, final failure and failure mode of mechanically fastened joints in composite laminates is presented. But this method is not applicable to double-shear joints.
257 citations
TL;DR: In this article, an analytical model based on cumulative damage was used for predicting the damage evolution in composite materials, verified with experimental data from a carbon/epoxy composite fatigued under tension-tension load.
195 citations
TL;DR: In this paper, a biaxial loading frame was developed to study the behavior of fiber reinforced composite laminates under static and cyclic in-plane complex stress states.
192 citations
TL;DR: In this paper, the effect of joint configuration, adhesive layer thickness, defects, humidity, spew fillet, and adherend stiffness were investigated by means of tension tests for glass-fiber reinforced vinylester composite laminates manufactured by resin infusion and bonded with an epoxy adhesive.
170 citations
TL;DR: Mitrevski et al. as mentioned in this paper investigated the post-impact damage properties of composite laminates impacted by various impactor shapes, including hemispherical, ogival and conical steel impactors.
144 citations
TL;DR: In this article, the authors investigate the damage mechanisms in self-reinforced polyethylene composite laminates (UHMWPE/HDPE) under monotonic tensile loading by the acoustic emission (AE) technique.
134 citations
TL;DR: In this article, the presence of through-thickness reinforcing pins decreases the tensile strength of the composite by 27% and the compressive strength of composite by at least 30%.
133 citations
TL;DR: In this article, an effective model of surface-bounded flat PZT disks based on effective force, moment and displacement is developed for Lamb wave excitation, collection and propagation in isotropic plate and quasi-isotropic laminated composite.
120 citations
TL;DR: In this paper, the authors presented an approach to detect surface cracks in various composite laminates using the differential quadrature method (DQM) to calculate strain energy using the mode shapes from both experimental and finite element analysis results.
118 citations
TL;DR: In this paper, the fatigue properties of magnetron sputtered Cu/Nb composite laminates with 40nm individual layer thickness were determined and the ratio of the fatigue endurance limit to the ultimate tensile strength was about 0.35.
TL;DR: In this paper, an embedded sensor network technique was developed for improving the overall integrity of functionalized composite structures engaged in aircraft, where a set of miniaturized piezoelectric wafers was designed and circuited to configure a built-in active actuator/sensor network, which was immobilized into multi-layered composite laminates.
Abstract: An embedded sensor network technique was developed for improving the overall integrity of functionalized composite structures engaged in aircraft. A set of miniaturized piezoelectric wafers was designed and circuited to configure a built-in active actuator/sensor network, which was immobilized into multi-layered composite laminates. The propagation characteristics of Lamb waves generated and collected by this built-in sensor network in carbon fibre-reinforced composite laminates were investigated. The influence of a stiffener and of the excitation frequency on the propagation of the Lamb waves generated was evaluated. A study was carried out to assess delamination in CF/EP (carbon fibre/epoxy) woven laminates, by fusing information from multiple sensing paths of the embedded network on the basis of the Hilbert transform, signal correlation and probabilistic searching. An excellent identification capability indicates the considerable application potential of the proposed sensor network approach in providing high-fidelity data acquisition and condition monitoring for composite aircraft structures.
TL;DR: In this article, a total fatigue life model for delaminated composite structures is presented, which includes the delamination growth in three domains, namely subcritical, linear, and final fracture.
TL;DR: In this article, a simulation of delamination during drilling of carbon/epoxy plates is performed using the finite element method, where the composite plate is modelled by successive layers, allowing the usage of different stacking sequences.
Abstract: In this paper, delamination during drilling of carbon/epoxy plates is analysed using the finite element method. The composite plate is modelled by successive layers, allowing the usage of different stacking sequences. The tool is modelled as a ‘rigid body’, and different tool geometries are compared, as well as axial thrust forces and delamination onset. The model simulations consider non-linear three-dimensional analysis and include the use of previously formulated interface finite elements incorporating a damage model based on fracture mechanics. Results are compared with experimental data. Important conclusions were drawn in order to decrease the probability of delamination occurrence.
TL;DR: In this paper, the tensile properties of carbon fiber laminate composites were evaluated by tensile tests according to the ASTM D3039, and the results indicated the importance of the adequate combination of the polymeric matrix and the reinforcement arrangement in the structural composite manufacture.
Abstract: Carbon fabric/epoxy composites are materials used in aeronautical industry to manufacture several components as flaps, aileron, landing-gear doors and others. To evaluate these materials become important to know their mechanical properties, for example, the tensile strength. Tensile tests are usually performed in aeronautical industry to determinate tensile property data for material specifications, quality assurance and structural analysis. For this work, it was manufactured four different laminate families (F155/PW, F155/HS, F584/PW and F584/HS) using pre-impregnated materials (prepregs) based on F155TM and F584TM epoxy resins reinforced with carbon fiber fabric styles Plain Weave (PW) and Eight Harness Satin (8HS). The matrix F155TM code is an epoxy resin type DGEBA (diglycidil ether of bisphenol A) that contains a curing agent and the F584TM code is a modified epoxy resin type. The laminates were obtained by handing lay-up process following an appropriate curing cycle in autoclave. The samples were evaluated by tensile tests according to the ASTM D3039. The F584/PW laminates presented the highest values of tensile strength. However, the highest modulus results were determined for the 8HS composite laminates. The correlation of these results emphasizes the importance of the adequate combination of the polymeric matrix and the reinforcement arrangement in the structural composite manufacture. The microscopic analyses of the tested specimens show valid failure modes for composites used in aeronautical industry.
TL;DR: In this paper, an electromagnetic riveting (EMR) technique is used to create a well-distributed shaft expansion, and can be used to conduct interference-fit riveting in composites structures.
TL;DR: In this article, the ability of hybrid light-weight fiber-reinforced polymer-matrix composite laminate armor to withstand the impact of a fragment simulating projectile (FSP) was investigated using a non-linear dynamics transient computational analysis.
TL;DR: In this article, the effect of temperature on the impact performance of Kevlar/fiberglass composite laminates was studied at several low velocity impact energy levels (8, 15 and 25 J) in the range of −50 to 120°C.
Abstract: This paper demonstrates results of an experimental study on Kevlar/fiberglass composite laminates subjected to impact loading at variable temperatures. The effect of temperature on maximum energy, elastic energy, maximum deflection, maximum impact force, ductility, and compression after impact was studied at several low velocity impact energy levels (8, 15 and 25 J). The temperatures considered were in the range of −50 to 120 °C. Results indicated that impact performance of these composites was affected over the range of temperature considered. Testing at ambient temperature is not fully sufficient and therefore additional testing must be performed for full understanding of composite laminate properties.
TL;DR: In this paper, the compressive failure mechanism of quasi-isotropic composite laminates with an open hole was experimentally and numerically studied to explain the mechanical meaning of the open hole compression (OHC) strength.
TL;DR: In this paper, a unified fatigue life model based on the energy method is developed for unidirectional polymer composite laminates subjected to constant amplitude, tension-tension or compression-compression fatigue loading.
TL;DR: It is suggested that the use of a safety factor for the objective function is more appropriate for maximizing for the faiure load.
Abstract: In designing composite laminates, minimization of a suitable failure criterion is sometimes selected as the objective function. However, for non-homogeneous criteria, e.g., the Tsai–Wu criterion, this objective function will not maximize the failure load, when it is carried at a load which is different from the failure load. We suggest that the use of a safety factor for the objective function is more appropriate for maximizing for the faiure load. In fact we show losses of more than 40% in the load carrying capacity even when the load carrying capacity of the optimal laminate is 75% of the applied load.
TL;DR: In this paper, the lifetime of E-glass vinyl ester composite laminates subjected to combined centric compression and one-sided simulated fire exposure was evaluated and shown to support a 10MPa compressive stress under low heat fluxes (20-30kW/m2).
Abstract: The structural response of continuous fiber, polymer matrix composites to fire exposure is presently of interest to the construction and marine industries. This paper addresses experimentally measured lifetime of E-glass vinyl ester composite laminates subjected to combined centric compression and one-sided simulated fire exposure. Under such conditions, these laminates (having a nearly quasi-isotropic stacking sequence) support a 10 MPa compressive stress under low heat fluxes (20–30 kW/m2) for approximately 102 s. Thermally modified micromechanics and laminate mechanics are successfully used to describe the observed life times when limited to thermal reversible effects. In these cases, the glass transition temperature controls the life the composite.
TL;DR: In this paper, a hybrid methodology consisting of experimental identification of damping, using vibration damping testing methods, and utilization of FEA was presented for predicting damping properties of composite laminates; this method could also be applied to homogeneous materials.
TL;DR: In this paper, an experimental investigation was conducted to study the behavior of unreinforced masonry (URM) walls retrofitted with composite laminates, which increased the stiffness and strength and enhanced the post-peak behavior by stabilizing the masonry walls and preventing their out-of-plane spalling.
TL;DR: In this paper, the influence of drilling-induced damage on the residual tensile strength of uni-directional composite laminates and a mathematical model correlating the residual strength with the drilling parameters was proposed.
Abstract: Uni-directional glass fiber reinforced plastic (UD-FRP) composite materials are a feasible alternative to structural members that bear loads in only one direction. FRP composite materials have excellent properties in the direction of the fibers. Drilling- induced damage acts as an inhibitor to their application, as the holes act as stress concentration sites for failure under loading. The present study is an attempt to study the influence of drilling-induced damage on the residual tensile strength of uni-directional composite laminates and to propose a mathematical model correlating the residual strength with the drilling parameters. A finite element model (FEM) is also developed to study the drilling-induced damage in composite laminates.
TL;DR: In this paper, the authors investigated edge delamination onset on composite laminate for a carbon/epoxy G947/M18 composite material, making use of a conventional model assuming plies homogeneity, damageable elastic behaviour, plane interlaminar surface also infinite interfacial stiffness and a local stress tensor correction near the edge.
TL;DR: In this paper, a variational formulation based on a Hu-Washizu functional with independent displacements, stress resultants and shell strains is proposed for thin composite structures and tested by several nonlinear examples including bifurcation and postbuckling response.
Abstract: The structural analysis of thin composite structures requires robust and effective shell elements. In this paper the variational formulation is based on a Hu–Washizu functional with independent displacements, stress resultants and shell strains. For the independent shell strains an additional interpolation part is introduced. This yields an improved convergence behaviour especially for laminated shells with coupled membrane and bending stiffness. The developed mixed hybrid shell element possesses the correct rank and fulfills the in–plane and bending patch test. The formulation is tested by several nonlinear examples including bifurcation and post–buckling response. The essential feature of the new element is the robustness in nonlinear computations with large rigid body motions. It allows very large load steps in comparison to standard displacement models.
TL;DR: In this article, the problem of interfacial shear stresses in beams strengthened with bonded prestressed composite laminates is analyzed using linear elastic theory, and a closed-form formula for calculating the critical maximum shear stress at the end of the laminate for a beam with arbitrary cross-section and material is provided.
Abstract: In this paper, the problem of interfacial shear stresses in beams strengthened with bonded prestressed composite laminates is analyzed using linear elastic theory. The analysis provided a closed-form formula for calculating the critical maximum shear stress at the end of the laminate for a beam with arbitrary cross-section and material. A demonstration study on strengthening an existing steel bridge using this technique has also been conducted using FE-analysis. The results from both analyses agreed very well. Also, a parametric study is performed in order to identify the effects of various geometrical and material properties on the magnitude of interfacial shear stresses. The results show that there exists high concentration of shear stresses at the ends of the laminate, which might result in a premature failure of the strengthening scheme at these locations. Material properties such as laminate and adhesive stiffness and the dimensions of the laminate where all found to have a marked effect on the magnitude of maximum shear stress in the composite member.
TL;DR: In this article, a moire interferometric investigation of surface strain redistribution due to matrix cracking around open holes in two [0/45/90/-45]s composite laminates with differing ply thicknesses was conducted.
Abstract: A moire interferometric investigation of surface strain redistribution due to matrix cracking around open holes in two [0/45/90/-45]s composite laminates with differing ply thicknesses was conducted. Both tests revealed significant redistribution of strain as damage developed. The results from the thicker-ply specimen show strain redistribution mostly due to the cracking of the top 0° ply. This was verified by a mesh-independent displacement discontinuity modeling method based on higher order shape functions. Localized effects of sub-surface-ply cracking were not found. However, due to a thinner surface ply and more extensive damage, the thinner-ply specimen showed significant redistribution of strain as a result of the sub-surface-ply cracking as well as the 0° ply cracking. Evidence of cracking in the center −45° plies was present in the strain results. Examination of the strain redistribution and the failure surface of the thinner ply specimen led to the development of a failure scenario, where the initiation of critical 0° fiber cracking occurs slightly away from the hole edge. Future modeling efforts will attempt to verify this scenario.
TL;DR: In this paper, a number of experimental round-robin data sets obtained using the mode I double cantilever beam (DCB) specimen to evaluate GIC for fiber composite laminates have been reanalysed with a view to determining additional parameters to describe micro-cracking and damage in the composite arm, and the bridging stresses at the crack tip.