Journal articles: 'Interlaminar transverse shear'

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Lu, Xianqiang, and Dahsin Liu. "An Interlaminar Shear Stress Continuity Theory for Both Thin and Thick Composite Laminates." Journal of Applied Mechanics 59, no. 3 (September 1, 1992): 502–9. http://dx.doi.org/10.1115/1.2893752.

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The interlaminar shear stress plays a very important role in the damage of composite laminates. With higher interlaminar shear stress, delamination can easily occur on the composite interface. In order to calculate the interlaminar shear stress, a laminate theory, which accounts for both the interlaminar shear stress continuity and the transverse shear deformation, was presented in this study. Verification of the theory was performed by comparing the present theory with Pagano’s elasticity analysis. It was found that the present theory was able to give excellent results for both stresses and displacements. More importantly, the interlaminar shear stress can be presented directly from the constitutive equations instead of being recovered from the equilibrium equations.

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Wang, Xiao Dan, and Guang Yu Shi. "Evaluation of Various Laminated Plate Theories Accounting for Interlaminar Transverse Shear Stress Continuity." Advanced Materials Research 716 (July 2013): 119–26. http://dx.doi.org/10.4028/www.scientific.net/amr.716.119.

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Based on a unified form of the plate kinematics in terms of the transverse shear functions and the Heaviside step function, the analytical solutions of laminated plates corresponding to a number of higher-order shear deformation plate theories are solved in this paper. The accuracy assessment of these higher-order laminated plate theories is conducted by comparing the resulting analytical solutions with the elasticity solutions and finite element results. The accuracy study shows that the interlaminar shear stress continuity condition is very important for the accurate prediction of the transverse shear stresses across the laminated plate thickness. The comparison study also indicates that the new laminated plate theory accounting for the interlaminar transverse shear stress continuity proposed by the authors yields both very accurate displacements and accurate stresses. This new higher-order laminated plate theory can be efficiently used in the finite element analysis of laminated composite plates since it uses the same five field variables as those used in the first-order shear deformation plate theory.

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Popper, P., C. Miller, D. L. Filkin, and W. J. Schaffers. "A Simple Model for Cornering and Belt-edge Separation in Radial Tires." Tire Science and Technology 14, no. 1 (January 1, 1986): 3–32. http://dx.doi.org/10.2346/1.2148765.

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Abstract A mathematical analysis of radial tire cornering was performed to predict tire deflections and belt-edge separation strains. The model includes the effects of pure bending, transverse shear bending, lateral restraint of the carcass on the belt, and shear displacements between belt and carcass. It also provides a description of the key mechanisms that act during cornering. The inputs include belt and carcass cord properties, cord angle, pressure, rubber properties, and cornering force. Outputs include cornering deflections and interlaminar shear strains. Key relations found between tire parameters and responses were the optimum angle for minimum cornering deflections and its dependence on cord modulus, and the effect of cord angle and modulus on interlaminar shear strains.

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Whitney, James M., and Anis Gawandi. "Effective interlaminar shear moduli in composites containing transverse ply cracks." Composites Science and Technology 66, no. 14 (November 2006): 2591–98. http://dx.doi.org/10.1016/j.compscitech.2006.01.005.

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Zhen, Wu, and Chen Wanji. "Interlaminar stress analysis of multilayered composites based on the Hu-Washizu variational theorem." Journal of Composite Materials 52, no. 13 (September 27, 2017): 1765–79. http://dx.doi.org/10.1177/0021998317733532.

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Up to date, accurate prediction of interlaminar stresses is still a challenging issue for two-node beam elements. The postprocessing approaches by integrating the three-dimensional equilibrium equation have to be used to obtain improved transverse shear stresses, whereas the equilibrium approach requires the first-order derivatives of in-plane stresses. In-plane stresses within two-node beam element are constant, so the first-derivatives of in-plane stresses are close to zero. Thus, two-node beam elements encounter difficulties for accurate prediction of transverse shear stresses by the constitutive equation or the equilibrium equation, so a robust two-node beam element is expected. A two-node beam element in terms of the global higher-order zig-zag model is firstly developed by employing the three-field Hu-Washizu mixed variational principle. By studying the effects of different boundary conditions, stacking sequence and loading on interlaminar stresses of multilayered composite beams, it is shown that the proposed two-node beam element yields more accurate results with lesser computational cost compared to various higher-order models. It is more important that accurate transverse shear stress has active impact on displacements and in-plane stresses of multilayered composite beams.

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Carrera, E. "A Reissner’s Mixed Variational Theorem Applied to Vibration Analysis of Multilayered Shell." Journal of Applied Mechanics 66, no. 1 (March 1, 1999): 69–78. http://dx.doi.org/10.1115/1.2789171.

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A comprehensive model of anisotropic multilayered double curved shells fulfilling a priori the interlaminar continuity requirements for the transverse shear and transverse normal stress as well as the static conditions on the bounding surfaces of the shell is developed in this paper. To this end, Reissner’s mixed variational theorem is employed to derive the equations governing the dynamic equilibrium and compatibility of each layer, while the interlaminar continuity conditions are used to drive the equations at the multilayered level. No assumptions have been made concerning the terms of type thickness to radii shell ratio h/R. Classical displacement formulations and related equivalent single layer equations have been derived for comparison purposes. Comparison of frequency predictions based upon the presented structural model with a number of results spread throughout the specialized literature and obtained via other models reveals that this advanced model provides results in excellent agreement with the ones based on three-dimensional elasticity theory, and better as compared to the ones violating the interlaminar stress continuity requirements and/or transverse normal stress and related effects.

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Koziol, Mateusz. "Experimental study on the effect of stitch arrangement on mechanical performance of GFRP laminates manufactured on a basis of stitched preforms." Journal of Composite Materials 46, no. 9 (October 4, 2011): 1067–78. http://dx.doi.org/10.1177/0021998311414947.

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This article presents the results of interlaminar shear and flexural tests of stitched polyester glass fiber laminates in dependence on stitch density and main geometric stitching parameters: stitch length and stitch spacing. Purpose of the study is to work out guidelines and indications for manufacturers of composite laminates who use or who plan to use stitching technique. It was found that stitching significantly improves interlaminar shear strength which increases with stitch density. However, stitching causes deterioration of in-plane flexural properties – the deterioration progresses when stitch density increases. Obtained results indicate that it is better to achieve increase in stitch density (resulting in improvement of interlaminar shear strength) by reduction of stitch length than by reduction of stitch spacing. Stitched laminate shows higher flexural strength and flexural modulus when bent into direction parallel to the stitch lines than when bent into the transverse direction. The results obtained within the study and their approximation constants may be a base for a new theoretical model simulating behavior of stitched laminate during static bending and enabling prediction of its mechanical performance.

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Woelke, Pawel, Ka-Kin Chan, Raymond Daddazio, Najib Abboud, and George Z. Voyiadjis. "Analysis of Shear Flexible Layered Isotropic and Composite Shells by ‘EPSA’." Shock and Vibration 19, no. 3 (2012): 459–75. http://dx.doi.org/10.1155/2012/179879.

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We present a simple and efficient method for the analysis of shear flexible isotropic and orthotropic composite shells. Classical thin shell constitutive equations used in the explicit finite element code EPSA to model homogenous isotropic shells using "through-the-thickness-integration" and layered orthotropic composite shells [1–3,5] are modified to account for transverse shear deformation. This effect is important in the analysis of thick plates and shells as well as composite laminates, where interlaminar effects matter. Transverse shear stresses are calculated using a linear normal strain distribution, where first the shear forces are calculated and then the stresses are calculated by means of the generalized section properties, i.e., first and second moments of area. The formulation is a generalization of the analytical method of analyzing composite beams. It is simple and computationally inexpensive, and it yields accurate results without employing higher order displacement interpolations. In the case of isotropic shells, the transverse shear stresses are distributed parabolically, based on the assumption of linear normal strain distribution through the thickness and on application of the quadratic shape function to transverse shear strains. The transverse shear stresses are included in the elastic-perfectly plastic yield function of the Huber-Mises-Hencky type.

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Luo, Quantian, and Liyong Tong. "Energy release rates for interlaminar delamination in laminates considering transverse shear effects." Composite Structures 89, no. 2 (June 2009): 235–44. http://dx.doi.org/10.1016/j.compstruct.2008.07.015.

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Ziao, J., and J. Tao. "Investigation of Interlaminar Defects and their Influence on Interlaminar Strength." Advanced Composites Letters 5, no. 4 (July 1996): 096369359600500. http://dx.doi.org/10.1177/096369359600500404.

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In this paper, we directed our attention to the interlaminar defects and their influence on the interlaminar strengths. With the aid of a S-570 scanning electron microscope, the morphology and distribution of interlaminar defects were inspected and documented. According to their shape, size and cause of formation, the defects were classified into five types: flakiness void, irregular shaped debond, local imperfectly cured resin, debond in two multi-directional plies, and inhomogeneous fibers and the large scale debond by these fibers. The cause of defects formation was discussed by analyzing the manufacturing process of composites. The influence of defects on the interlaminar strength and its mechanism was analyzed experimentally and theoretically. The results indicate that these defects, with different effects, decrease the interlaminar strength because they form interlaminar cracks, and the interlaminar shear strength is less affected than interlaminar tensile strength, which is measured according to GB4944 test method. To comprehend defects distribution effect, a four-point-bending test method was introduced to measure the interlaminar peel strength, and a discussion was made on the correlation between the interlaminar tensile strength, interlaminar peel strength and in-plane transverse tensile strength. Finally the concept of interlaminar defect coefficient, which can be used to characterize the defects, was set up and the formula to calculate it was proposed.

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Fu, Yu, Xingzhong Tang, Qilin Jin, and Zhen Wu. "An Alternative Electro-Mechanical Finite Formulation for Functionally Graded Graphene-Reinforced Composite Beams with Macro-Fiber Composite Actuator." Materials 14, no. 24 (December 16, 2021): 7802. http://dx.doi.org/10.3390/ma14247802.

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With its extraordinary physical properties, graphene is regarded as one of the most attractive reinforcements to enhance the mechanical characteristics of composite materials. However, the existing models in the literature might meet severe challenges in the interlaminar-stress prediction of thick, functionally graded, graphene-reinforced-composite (FG-GRC)-laminated beams that have been integrated with piezoelectric macro-fiber-composite (MFC) actuators under electro-mechanical loadings. If the transverse shear deformations cannot be accurately described, then the mechanical performance of the FG-GRC-laminated beams with MFC actuators will be significantly impacted by the electro-mechanical coupling effect and the sudden change of the material characteristics at the interfaces. Therefore, a new electro-mechanical coupled-beam model with only four independent displacement variables is proposed in this paper. Employing the Hu–Washizu (HW) variational principle, the precision of the transverse shear stresses in regard to the electro-mechanical coupling effect can be improved. Moreover, the second-order derivatives of the in-plane displacement parameters have been removed from the transverse-shear-stress components, which can greatly simplify the finite-element implementation. Thus, based on the proposed electro-mechanical coupled model, a simple C0-type finite-element formulation is developed for the interlaminar shear-stress analysis of thick FG-GRC-laminated beams with MFC actuators. The 3D elasticity solutions and the results obtained from other models are used to assess the performance of the proposed finite-element formulation. Additionally, comprehensive parametric studies are performed on the influences of the graphene volume fraction, distribution pattern, electro-mechanical loading, boundary conditions, lamination scheme and geometrical parameters of the beams on the deformations and stresses of the FG-GRC-laminated beams with MFC actuators.

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Kesba, Mohamed Khodjet, Noureddine El Meiche, and A. Benkhedda. "Stress Distribution on the Cracked Sandwich Plate with Non Linear Thermal and Moisture Concentration." Nano Hybrids and Composites 32 (April 2021): 45–62. http://dx.doi.org/10.4028/www.scientific.net/nhc.32.45.

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The influence of linear and non-linear temperature and moisture concentration distribution on the stress distribution was studied for metal/ceramic sandwich plate with transverse cracks. An interlaminar adhesive layer between two different layers is taken into account which transferring the normal stress and the interlaminar shear stress. The validation of the used model was done with the comparison of the stiffness reduction as a function of crack density and the experimental data. A comparison showed that a satisfactory qualitative and quantitative agreement was obtained. The temperature and moisture concentration variation are studied using the linear and non-linear distribution around the cracks to predict the stress distributions along the axis x. Finally, it observed through this study that the variations of the thermal and moisture concentration distribution largely impact the stress distribution for a sandwich plate with transverse cracks in the central layer and also with different mechanical properties of each layers.

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Chaudhuri, Reaz A. "Effects of thickness and fibre misalignment on compression fracture in cross-ply (very) long cylindrical shells under external pressure." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2180 (August 2015): 20150147. http://dx.doi.org/10.1098/rspa.2015.0147.

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Combined effects of modal imperfections, transverse shear/normal deformation with/without reduced transverse shear modulus, G LT (caused by distributed fibre misalignments), on emergence of interlaminar shear crippling type instability modes, related to localization (onset of deformation softening), delocalization (onset of deformation hardening) and propagation of mode II compression fracture/damage, in thick imperfect cross-ply very long cylindrical shells (plane strain rings) under applied hydrostatic pressure, are investigated. Of special interest is the question: what are the geometric and/or material parameters that induce localized and delocalized states in imperfect cross-ply (very) long cylindrical shells under hydrostatic compression simultaneously, and what would be the consequences of such occurrences? The primary accomplishment is the (hitherto unavailable) computation of the layer-wise mode II stress intensity factor, energy release rate and kink–crack bandwidth, under hydrostatic compression, from a nonlinear finite-element analysis, using Maxwell's construction and Griffith's energy balance approach. Additionally, the shear crippling angles in the layers are determined using an analysis, pertaining to the elastic inextensional deformation of the compressed (plane strain) ring. Numerical results include effects of (i) thickness-induced transverse shear/normal deformation and (ii) uniformly distributed fibre misalignments, on localization and delocalization, and consequently on compression fracture/damage characteristics of thick imperfect cross-ply very long cylindrical shells.

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LV, XIAOJUN, QI ZHANG, GUOJUN XIE, and GUANJIE LIU. "DEGRADATION OF CARBON FIBER/EPOXY COMPOSITES BY XE LAMP AND HUMIDITY." International Journal of Modern Physics B 20, no. 25n27 (October 30, 2006): 3686–91. http://dx.doi.org/10.1142/s0217979206040209.

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In order to understand the effect of natural environmental factors on the carbon fiber/epoxy composites, the degradation of carbon fiber/epoxy composite was studied. The specimens were exposed in a Xe lamp chamber and suffered to ultraviolet light radiation, temperature and/or humidity conditions. The results show that the radiation, temperature and/or humidity could cause extensive corrosion to the surface and interior of the carbon/epoxy composite and attack the interface between matrix and carbon fiber, resulting in an obvious reduction of the transverse tensile strength and interlaminar shear strength. On the contrary, the longitudinal transverse shear strength was not affected much by the radiation, temperature and/or humidity. The results indicate that the radiation, temperature and/or humidity can result in the corrosion of the carbon/epoxy composite and consequently affect the mechanical properties of the carbon/epoxy composite partially.

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Sekhavatjou, Mohammad, Mojtaba Azhari, and Saeid Sarrami-Foroushani. "Bubble Complex Finite Strip Method in the Stability and Vibration Analysis of Orthotropic Laminated Composite Plates." International Journal of Applied Mechanics 12, no. 09 (November 2020): 2050106. http://dx.doi.org/10.1142/s1758825120501069.

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In this study, a bubble complex finite strip method (BCFSM) with the higher-order zigzag theory is formulated for mechanical buckling and free vibration analysis of laminated composite plates, including cross-ply and angle-ply laminates. Few studies have been done to obtain the analytical solutions for clamped and free boundary conditions in the longitudinal and transverse edges. Therefore, this study, for the first time, investigates the effects of various boundary conditions on the stability and vibration results of laminated composite plates subjected to axial or pure shear forces with the use of higher-order zigzag theory and BCFSM. Following this, both the interlaminar continuity conditions of transverse shear stresses and the shear-free surface conditions are satisfied by applying a cubic displacement and a zigzag linear varying displacement with the same number of unknowns as the first-order shear deformation theories. Moreover, the effects of width-to-thickness ratio, fiber orientation, number of modes, different dimensional ratios of the plate, and finally, the number of layers are investigated through numerical examples. The bubble shape functions are exploited in the transverse direction to improve the convergence of the method. Finally, the shearing and axial interaction diagrams of composite laminated plates are presented for various types of boundary conditions.

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Li, Wen, Wei Chen, Liqun Tang, Zhenyu Jiang, and Peiyan Huang. "A general strength model for fiber bundle composites under transverse tension or interlaminar shear." Composites Part A: Applied Science and Manufacturing 121 (June 2019): 45–55. http://dx.doi.org/10.1016/j.compositesa.2019.03.009.

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Carrera, E. "Transverse Normal Stress Effects in Multilayered Plates." Journal of Applied Mechanics 66, no. 4 (December 1, 1999): 1004–12. http://dx.doi.org/10.1115/1.2791769.

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An evaluation of transverse normal stress σzz effects in multilayered plate modeling is given in this paper. Mixed theories with continuous interlaminar transverse shear and normal stresses have been formulated on the basis of Reissner's theorem (Reissner, 1984). The case in which the number of the displacement variables preserves independence by the number of constitutive layers, N1, has been investigated. Classical models based on standard displacement formulations have been discussed for comparison purposes. The analysis of transverse stress effects has been conducted by allowing a constant, linear, and higher-order distribution of the transverse displacement components in the plate thickness directions. Related two-dimensional models are compared for the static response of symmetrically and unsymmetrically layered, simply supported plates made of isotropic as well as orthotropic layers. The conducted numerical investigation and comparison with available results have above all led to the following conclusions. The possibility of including σzz makes the used mixed theories more attractive that other available modelings. σzz plays a fundamental role in thick laminate plates analysis. Such a role increases in transversely anisotropic multilayered plate analysis. With an increase of the plate thickness, a very accurate description of σzz requires modelings whose number of independent variables depends on N1.

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Khadem, M., and M. M. Kheirikhah. "Bending Analysis of SMA Embedded Rectangular Laminated Sandwich Plates with Soft Core Using 3D Finite Element Method." Applied Mechanics and Materials 110-116 (October 2011): 1458–65. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.1458.

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Nowadays Shape Memory Alloys (SMAs) are used as actuators in many applications such as aerospace structures. In sandwich structures, the SMA wires or plates are used in the skins for shape control of the structure or vibration damping. In this paper, bending behavior of sandwich plates with embedded SMA wires in their skins is studied. 3D finite element method is used for construction and analysis of the sandwich plate with a flexible core and two stiff skins. Some important points such as continuity conditions of the displacements, satisfaction of interlaminar transverse shear stresses, the conditions of zero transverse shear stresses on the upper and lower surfaces and in-plane and transverse flexibility of soft core are considered for accurate modeling and analysis of sandwich structures. Solution for bending analysis of sandwich plates under various transverse loads are presented and the effect of many parameters such as plate dimensions, loading conditions, material properties of core, skins and SMA wires are studied. Comparison of the present results in special case with those of the three-dimensional theory of elasticity and some plate theories confirms the accuracy of the proposed model.

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Zhang, Dongjian, Xitao Zheng, Chongzhe Wang, and Zhen Wu. "Experiments and Analysis on Stability of the Sandwich Structures with Soft Core." International Journal of Structural Stability and Dynamics 19, no. 12 (December 2019): 1950159. http://dx.doi.org/10.1142/s0219455419501591.

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In this paper, first a complete buckling experiment of the sandwich beams with the foam core is carried out, which includes the manufacturing of specimens and their experimental verification. Second, a refined sinusoidal zig-zag theory (RSZT) is established, which can describe the zig-zag effect during the in-plane compression of sandwich beam and accommodate the transverse shear free surface boundary conditions. Based on the established model combined with Hu–Washizu variational principle, a two-node beam element has been developed to address the buckling problem of the sandwich beams. Thus, the established beam element is able to accommodate interlaminar continuous conditions of transverse shear stress. Several examples have been investigated to validate the accuracy of the established method. The comparative analysis of the results including experimental data, the results acquired from three-dimensional finite element (3D-FEM) and diverse models has been made. Comparative analysis shows that the accurate buckling loads can be acquired from the established model. Nevertheless, other models discarding the continuous conditions of transverse stresses among the adjacent layers largely overestimate the critical loads.

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Sekulić, D. R., I. M. Djordjević, M. V. Gordić, Zijah Burzić, and M. M. Stevanović. "Gamma Radiation Effects on Mechanical Properties of Carbon/Epoxy Composites." Materials Science Forum 518 (July 2006): 549–54. http://dx.doi.org/10.4028/www.scientific.net/msf.518.549.

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Unidirectional and angle-ply carbon/epoxy laminates were gamma irradiated up to doses of 12 and 20 MGy. Composites with two different, low and high temperature epoxy matrices have been submitted to irradiation and subsequent mechanical testing. The radiation effects were studied by measuring in-plane, interalminar shear and transverse tensile strength, as well as interlaminar strain energy release rate of tested composites. The immersion of composite plate in water at 80 oC and mechanical measurements at elevated temperatures emphasized irradiation effects on mechanical properties.

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Sánchez-Romate, Xoan F., Andrés Alvarado, Alberto Jiménez-Suárez, and Silvia G. Prolongo. "Carbon Nanotube Reinforced Poly(ε-caprolactone)/Epoxy Blends for Superior Mechanical and Self-Sensing Performance in Multiscale Glass Fiber Composites." Polymers 13, no. 18 (September 18, 2021): 3159. http://dx.doi.org/10.3390/polym13183159.

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In this paper, a novel carbon nanotube (CNT) polycaprolactone (PCL), epoxy, and glass fiber (GF) composite is reported. Here, the nanoreinforced composites show a flexural strength increase of around 30%, whereas the interlaminar shear strength increases by 10–15% in comparison to unenhanced samples. This occurs because the addition of the CNTs induces a better PCL/epoxy/GF interaction. Furthermore, the nanoparticles also give novel functionalities to the multiscale composite, such as strain and damage monitoring. Here, the electrical response of the tensile- and compressive-subjected faces was simultaneously measured during flexural tests as well as the transverse conductivity in interlaminar tests, showing an exceptional capability for damage detection. Moreover, it was observed that the electrical sensitivity increases with PCL content due to a higher efficiency of the dispersion process that promotes the creation of a more uniform electrical network.

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Dadej, Konrad, Paolo Sebastiano Valvo, and Jarosław Bieniaś. "The Effect of Transverse Shear in Symmetric and Asymmetric End Notch Flexure Tests–Analytical and Numerical Modeling." Materials 13, no. 14 (July 8, 2020): 3046. http://dx.doi.org/10.3390/ma13143046.

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This paper focuses on the effects of transverse shear and root rotations in both symmetric and asymmetrical end-notched flexure (AENF) interlaminar fracture toughness tests. A theoretical model is developed, whereas the test specimen is subdivided into four regions joined by a rigid interface. The differential equations for the deflection and rotations of each region are solved within both the Euler–Bernoulli simple beam theory (SBT) and the more refined Timoshenko beam theory (TBT). A concise analytical equation is derived for the AENF deflection profile, compliance, and transverse shearing forces as a function of the specimen geometry, stacking sequence, delamination length, and fixture span. Modeling results are compared with numerical finite element analyses, obtaining a very good agreement. Performed analyses suggest that even in the case of symmetrical and unidirectional laminates considered as pure mode II fracture, a complex compression/tension and bending moment state is present, as well as a slight contribution of anti-planar shear at the vicinity of the crack tip.

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Hu, Qiaole, Hafeezullah Memon, Yiping Qiu, and Yi Wei. "The Failure Mechanism of Composite Stiffener Components Reinforced with 3D Woven Fabrics." Materials 12, no. 14 (July 10, 2019): 2221. http://dx.doi.org/10.3390/ma12142221.

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Composite industry has long been seeking practical solutions to boost laminate through-thickness strengths and interlaminar shear strengths (ILSS), so that composite primary structures, such as stiffeners, can bear higher complex loadings and be more delamination resistant. Three dimensional (3D) woven fabrics were normally employed to render higher transverse and shear strengths, but the difficulty and high expense in producing such fabrics make it a hard choice. Based on a novel idea that the warp yarns that interlock layers of the weft yarns might provide adequate fiber crimps that would allow the interlaminar shear or radial stresses to be transferred and borne by the fibers, rather than by the relatively weaker matrix resin, thus improving the transverse strengths, this work provided a two point five dimensional (2.5D) approach as a practical solution, and demonstrated the superior transverse performances of an economical 2.5D shallow-bend woven fabric (2.5DSBW) epoxy composites, over the conventional two dimensional (2D) laminates and the costly 3D counterpart composites. This approach also produced a potential candidate to fabricate high performance stiffeners, as shown by the test results of L-beams which are common structural components of any stiffeners. This study also discovered that an alternative structure, namely a 2.5D shallow-straight woven fabric (2.5DSSW), did not show any advantages over the two control structures, which were a 2D plain weave (2DPW) and a 3D orthogonal woven fabric (3DOW) made out of the same carbon fibers. Composites of these structures in this study were conveniently fabricated using a vacuum-assisted resin infusion process (VARI). The L-beams were tested using a custom-made test fixture. The strain distribution and failure mode analysis of these beams were conducted using Digital Image Correlation (DIC) and X-ray Computed Tomography Scanning (CT). The results demonstrated that the structures containing Z-yarns or having high yarn crimps or waviness, such as in cases of 3DOW and 2.5DSBW, respectively, were shown to withstand high loadings and to resist delamination, favorable for the applications of high-performance structural composites.

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Kashtalyan, M., and C. Soutis. "Modelling of stiffness degradation due to cracking in laminates subjected to multi-axial loading." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2071 (July 13, 2016): 20160017. http://dx.doi.org/10.1098/rsta.2016.0017.

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The paper presents an analytical approach to predicting the effect of intra- and interlaminar cracking on residual stiffness properties of the laminate, which can be used in the post-initial failure analysis, taking full account of damage mode interaction. The approach is based on a two-dimensional shear lag stress analysis and the equivalent constraint model of the laminate with multiple damaged plies. The application of the approach to predicting degraded stiffness properties of multidirectional laminates under multi-axial loading is demonstrated on cross-ply glass/epoxy and carbon/epoxy laminates with transverse and longitudinal matrix cracks and crack-induced transverse and longitudinal delaminations. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

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Radzuan, Nabilah Afiqah Mohd, Abu Bakar Sulong, Anil Verma, and Norhamidi Muhamad. "Layup sequence and interfacial bonding of additively manufactured polymeric composite: A brief review." Nanotechnology Reviews 10, no. 1 (January 1, 2021): 1853–72. http://dx.doi.org/10.1515/ntrev-2021-0116.

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Abstract Additively manufactured polymeric composites exhibit customised properties beyond those offered by conventionally fabricated ones. However, in many cases, the mechanical performance mainly depends on the processing parameters, tools, and material selection. Yet, one of the issues of the additive manufacturing process especially in the material extrusion process is the inability to control the printing layups, thereby causing interlaminar damage. Thus far, literature and research have focused on improving the mechanical performance of such polymeric composites by focusing on the interlaminar shear strength under a transverse load transfer. Polymeric composites prepared using the material extrusion technique namely fused deposition modelling (FDM) are discussed upon its layup sequence and orientation. This article proposes that by realising a homogenous distribution of the transverse load, the orientation and the printing direction can maximise the printed load bearing. Moreover, the layup sequence and the interlayer diffusion are key for controlling the mechanical properties of the polymeric composites. This brief review presents a comprehensive elucidation of the polymeric composites manufactured using FDM that interprets the needs of having greater load bearing in each layup printing sequence of the polymeric composites. By able to control the layup sequence, one can control the mechanical performance based on specific functionality.

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Anish, Ajay Kumar, and Anupam Chakrabarti. "Influence of openings and additional mass on vibration of laminated sandwich rhombic plates using IHSDT." Journal of Thermoplastic Composite Materials 33, no. 1 (October 11, 2018): 3–34. http://dx.doi.org/10.1177/0892705718785682.

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In this article, investigations on the influence of openings and additional mass on free vibration analysis of laminated composite sandwich skew plates using improved higher order shear deformation theory (IHSDT) have been done. The IHSDT model satisfies the interlaminar shear stress continuity at the layer interfaces and also ensures zero transverse shear stress conditions at the top and bottom of the plate. The piecewise parabolic shear stress variation across the thickness of each layer is considered. No shear correction factors are required. The 2-D C0 finite element (FE) model has been developed by authors based on IHSDT. FE model based on IHSDT has been coded in FORTRAN. The problem of C1 continuity requirement associated with the IHSDT is overcome using an appropriate C0 FE formulation. The free vibration frequencies of laminated composite and sandwich plates obtained using the present 2-D FE model are in good agreement with the 3-D elasticity results. The influence of the side-to-thickness ratio, skew angles, boundary conditions, and mode shapes is taken into consideration for the present study.

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Chaudhuri, Reaz A. "Localization, Delocalization, and Compression Fracture in Moderately Thick Transversely Isotropic Bilinear Rings Under External Pressure." Journal of Engineering Materials and Technology 128, no. 4 (July 11, 2006): 603–10. http://dx.doi.org/10.1115/1.2345453.

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A fully nonlinear finite element analysis for prediction of localization∕delocalization and compression fracture of moderately thick imperfect transversely isotropic rings, under applied hydrostatic pressure, is presented. The combined effects of modal imperfections, transverse shear∕normal deformation, geometric nonlinearity, and bilinear elastic (a special case of hypoelastic) material property on the emergence of interlaminar shear crippling type instability modes are investigated in detail. An analogy to a soliton (slightly disturbed integrable Hamiltonian system) helps understanding the localization (onset of deformation softening) and delocalization (onset of deformation hardening) phenomena leading to the compression damage∕fracture at the propagation pressure. The primary accomplishment is the (hitherto unavailable) computation of the mode II fracture toughness (stress intensity factor∕energy release rate) and shear damage∕crack bandwidth, under compression, from a nonlinear finite element analysis, using Maxwell’s construction and Griffith’s energy balance approach. Additionally, the shear crippling angle is determined using an analysis, pertaining to the elastic plane strain inextensional deformation of the compressed ring. Finally, the present investigation bridges a gap of three or more orders of magnitude between the macro-mechanics (in the scale of mms and up) and micro-mechanics (in the scale of microns) by taking into account the effects of material and geometric nonlinearities and combining them with the concepts of phase transition via Maxwell construction and Griffith-Irwin fracture mechanics.

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Tang, Youhong, Lin Ye, Donghai Zhang, and Shiqiang Deng. "Characterization of transverse tensile, interlaminar shear and interlaminate fracture in CF/EP laminates with 10wt% and 20wt% silica nanoparticles in matrix resins." Composites Part A: Applied Science and Manufacturing 42, no. 12 (December 2011): 1943–50. http://dx.doi.org/10.1016/j.compositesa.2011.08.019.

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Bilisik, Kadir, Gulhan Erdogan, Erdal Sapanci, and Sila Gungor. "Three-dimensional nanoprepreg and nanostitched aramid/phenolic multiwall carbon nanotubes composites: Experimental determination of in-plane shear." Journal of Composite Materials 53, no. 28-30 (June 2, 2019): 4077–96. http://dx.doi.org/10.1177/0021998319854211.

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In-plane shear of nanostitched three-dimensional para-aramid/phenolic composites were experimentally investigated. Adding the nanostitched fiber into nanoprepreg para-aramid fabric preform composites slightly improved their shear strengths. The carbon-stitched composite exhibited comparatively better performance compared to the para-aramid stitched composite probably due to well bonding between carbon fiber and phenolic resin. The stitched nano composites had mainly matrix breakages and micro shear hackles in the matrix; matrix debonding and filament pull-out in the composite interface; fibrillar peeling and stripping on the filaments due to angular deformation. This mechanism probably prohibited extensive interlaminar opening in the nanostitched composites. The result exhibited that the introducing of the nano stitched fiber where multiwall carbon nanotubes were transferred to the out-of-plane of the base structure enhanced its transverse fracture as a form of confined delamination area. Therefore, the damaged tolerance properties of the stitched nano composites were enhanced compared to the base.

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Singh, S. K., and A. Chakrabarti. "Static, Vibration and Buckling Analysis of Skew Composite and Sandwich Plates Under Thermo Mechanical Loading." International Journal of Applied Mechanics and Engineering 18, no. 3 (August 1, 2013): 887–98. http://dx.doi.org/10.2478/ijame-2013-0053.

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Abstract Static, vibration and buckling behavior of laminated composite and sandwich skew plates is studied using an efficient C0 FE model developed based on refined higher order zigzag theory. The C0 FE model satisfies the interlaminar shear stress continuity at the interfaces and zero transverse shear stress conditions at plate top and bottom. In this model, the first derivatives of transverse displacement have been treated as independent variables to overcome the problem of C1 continuity associated with the plate theory. The C0 continuity of the present element is compensated in the stiffness matrix formulation by adding a suitable term. In order to avoid stress oscillations observed in the displacement based finite element, the stress field derived from temperature is made consistent with the total strain field by using field consistent approach. Numerical results are presented for different static, vibration and buckling problems by applying the FE model under thermo mechanical loading, where a nine noded C0 continuous isoparametric element is used. It is observed that there are very few results available in the literature on laminated composite and sandwich skew plates based on refined theories. As such many new results are also generated for future reference

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Li, N., P. H. Chen, and Q. Ye. "A damage mechanics model for low-velocity impact damage analysis of composite laminates." Aeronautical Journal 121, no. 1238 (March 6, 2017): 515–32. http://dx.doi.org/10.1017/aer.2017.6.

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ABSTRACTA method was developed to predict numerically the damage of composite laminates with multiple plies under low-velocity impact loading. The Puck criterion for 3D stress states was adopted to model the intralaminar damage including matrix cracking and fibre breakage, and to obtain the orientation of the fracture plane due to matrix failure. According to interlaminar delamination mechanism, a new delamination criterion was proposed. The influence of transverse and through-thickness normal stress, interlaminar shear stress and damage conditions of adjacent plies on delamination was considered. In order to predict the impact-induced damage of composite laminates with more plies quickly and efficiently, an approach, which can predict the specific damage of several plies in a single solid element, was proposed by interpolation on the strains of element integration points. Moreover, the proposed model can predict specific failure modes. A good agreement between the predicted delamination shapes and sizes and the experimental results shows correctness of the developed numerical method for predicting low-velocity impact damage on composite laminates.

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Punera, Devesh, and Tarun Kant. "Two dimensional kinematic models for CNT reinforced sandwich cylindrical panels with accurate transverse interlaminar shear stress estimation." Thin-Walled Structures 164 (July 2021): 107881. http://dx.doi.org/10.1016/j.tws.2021.107881.

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Wang, X., and G. Shi. "A refined laminated plate theory accounting for the third-order shear deformation and interlaminar transverse stress continuity." Applied Mathematical Modelling 39, no. 18 (September 2015): 5659–80. http://dx.doi.org/10.1016/j.apm.2015.01.030.

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Gupta, Shambhu K., and Mehdi Hojjati. "Thermal cycle effects on laminated composite plates containing voids." Journal of Composite Materials 53, no. 4 (July 12, 2018): 489–501. http://dx.doi.org/10.1177/0021998318786785.

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Composite structures are often cured in an autoclave to acquire the required space grade quality. Now the industry is focusing on the out of autoclave manufacturing method which leads to more voids inside laminate with respect to those manufactured in the autoclave. In the present work, the influence of voids on microcrack formation under thermal cycling and environmental conditions was analyzed. Thermal cycle experiments were performed using liquid nitrogen and oven, followed by microscopic observation of the polished cross-section of the 90° layered plies. Cracks were monitored, counted, and measured with respect to void and void free areas. Void content was characterized using microscopic and ImageJ software was used. It was observed that the microcracks will be formed both around the voids and in void free areas. As the number of thermal cycle increases, the number of microcrack around the voids increases much faster than compared to the void free areas. Also it was observed that most of microcracks were propagated in the transverse direction. Interlaminar shear strength was measured. Results indicate that interlaminar shear strength reduces as the number of cycle rises due to the increase in the microcrack density. Finite element method was used to simulate the process. The micro, meso, and macro model were created with respect to original samples voids and positions to calculate the stress distribution and its concentration. Good agreement between experiment and simulation was observed.

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Chen, Wei Dong, Ping Jia, Jian Cao Li, Feng Chao Zhang, Yan Chun Yu, Sheng Zhuo Lu, and Lei Shao. "The Interlaminar Stresses Analysis of Composite Laminated Plates Based on the Generalized Higher-Order Global-Local Plate Theory." Advanced Materials Research 785-786 (September 2013): 239–43. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.239.

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A generalized higher-order global-local theory was presented. The transverse shear stresses can be got directly through the constitutive equation without using the equilibrium equation. The second derivative of interpolation function was deduced. The hammer integration of triangular area coordinate method was applied to solve the multiple integration problem of the element stiffness matrix. The order choice of numerical integration was discussed and results obtained through two different integration orders were compared. The flow of how to compile a FORTRAN program was given. A moderately thick composite laminated plate was analyzed via finite element method (FEM) based on the theory and results were compared with that of Paganos three-dimensional elasticity. It shows that the interlaminar stresses are accurate for moderately thick laminated plates.

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Kasa, Temesgen Takele. "Consideration of interlaminar strain–energy continuity in composite plate analysis using improved higher order theory." Transactions of the Canadian Society for Mechanical Engineering 42, no. 3 (September 1, 2018): 211–21. http://dx.doi.org/10.1139/tcsme-2017-0102.

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The main goal of this paper is to suggest an improved higher order refined theory for analysing perfectly bonded stacked composite laminates with the usual lamination configurations. The analysis incorporates continuous flexural and in-plane displacements at the interfaces. Furthermore, the transverse shear stress is continuous and constrained with the Lagrange multiplier technique by introducing 14 new unknown variables that are expressed in terms of the interfacial strain energy, which is assuming to be continuous throughout the thickness of the laminate. To determine the newly introduced flexural and in-plane unknown variables, the total potential energy is minimised using variational calculus. The numerical results are compared with those from existing reliable published papers. In general, the proposed approach is sufficient for analysing laminate structures with the required accuracy.

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Carrera, Erasmo. "Assessment of Theories for Free Vibration Analysis of Homogeneous and Multilayered Plates." Shock and Vibration 11, no. 3-4 (2004): 261–70. http://dx.doi.org/10.1155/2004/493584.

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This paper assesses classical and advanced theories for free vibrational response of homogeneous and multilayered simply supported plates. Closed form solutions are given for thick and thin geometries. Single layer and multilayered plates made of metallic, composite and piezo-electric materials, are considered. Classical theories based on Kirchhoff and Reissner-Mindlin assumptions are compared with refined theories obtained by enhancing the order of the expansion of the displacement fields in the thickness directionz. The effect of the Zig-Zag form of the displacement distribution inzas well as of the Interlaminar Continuity of transverse shear and normal stresses at the layer interface were evaluated. A number of conclusions have been drawn. These conclusions could be used as desk-bed in order to choose the most valuable theories for a given problem.

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Costa, Kevin D., Yasuo Takayama, Andrew D. McCulloch, and James W. Covell. "Laminar fiber architecture and three-dimensional systolic mechanics in canine ventricular myocardium." American Journal of Physiology-Heart and Circulatory Physiology 276, no. 2 (February 1, 1999): H595—H607. http://dx.doi.org/10.1152/ajpheart.1999.276.2.h595.

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Previous studies suggest that the laminar architecture of left ventricular myocardium may be critical for normal ventricular mechanics. However, systolic three-dimensional deformation of the laminae has never been measured. Therefore, end-systolic finite strains relative to end diastole, from biplane radiography of transmural markers near the apex and base of the anesthetized open-chest canine anterior left ventricular free wall ( n = 6), were referred to three-dimensional laminar microstructural axes reconstructed from histology. Whereas fiber shortening was uniform [−0.07 ± 0.04 (SD)], radial wall thickening increased from base (0.10 ± 0.09) to apex (0.14 ± 0.13). Extension of the laminae transverse to the muscle fibers also increased from base (0.08 ± 0.07) to apex (0.11 ± 0.08), and interlaminar shear changed sign [0.05 ± 0.07 (base) and −0.07 ± 0.09 (apex)], reflecting variations in laminar architecture. Nevertheless, the apex and base were similar in that at each site laminar extension and shear contributed ∼60 and 40%, respectively, of mean transmural thickening. Kinematic considerations suggest that these dual wall-thickening mechanisms may have distinct ultrastructural origins.

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Hou, J., and George Jeronimidis. "Finite Element Aided Design Evolution of Composite Leaf Spring." Applied Mechanics and Materials 3-4 (August 2006): 429–34. http://dx.doi.org/10.4028/www.scientific.net/amm.3-4.429.

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This paper shows the process of the virtual production development of the mechanical connection between the top leaf of a dual composite leaf spring system to a shackle using finite element methods. The commercial FEA package MSC/MARC has been used for the analysis. In the original design the joint was based on a closed eye-end. Full scale testing results showed that this configuration achieved the vertical proof load of 150 kN and 1 million cycles of fatigue load. However, a problem with delamination occurred at the interface between the fibres going around the eye and the main leaf body. To overcome this problem, a second design was tried using transverse bandages of woven glass fibre reinforced tape to wrap the section that is prone to delaminate. In this case, the maximum interlaminar shear stress was reduced by a certain amount but it was still higher than the material’s shear strength. Based on the fact that, even with delamination, the top leaf spring still sustained the maximum static and fatigue loads required, the third design was proposed with an open eye-end, eliminating altogether the interface where the maximum shear stress occurs. The maximum shear stress predicted by FEA is reduced significantly and a safety factor of around 2 has been obtained. Thus, a successful and safe design has been achieved.

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Sockalingam, Subramani, John W. Gillespie, and Michael Keefe. "Influence of multiaxial loading on the failure of Kevlar KM2 single fiber." Textile Research Journal 88, no. 5 (December 8, 2016): 483–98. http://dx.doi.org/10.1177/0040517516681961.

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The role of multiaxial loading on the failure of Kevlar® KM2 ballistic fibers during transverse loading is not well understood. Quasi-static experiments reported by Hudspeth M, Li D, Spatola J, et al. (2015) on single KM2 fiber subjected to transverse loading by three indenter geometries over a wide range of loading angles exhibit significant reductions in the average axial tensile failure strain. In this study, a three-dimensional finite element model is developed to predict the degree of multiaxial loading present at the location of fiber failure in these experiments. The model predicts an axial tensile strain concentration within the indenter–fiber contact zone. The fiber is also subjected to multiaxial stress/strain states within the contact zone consisting of axial tension, axial compression, transverse compression and interlaminar shear that can degrade axial tensile failure strain. For a round indenter with a radius much higher than the fiber diameter, the axial tensile strain concentration and multiaxial strain in the fiber are negligible. In the case of a fragment-simulating projectile and a razor indenter, significant axial tensile strain concentrations (2.2–5.9) are predicted and the localized transverse loading results in extensive inelastic deformation within the fiber cross-section. Based on the results, a maximum axial tensile strain failure criterion incorporating the multiaxial loading degradation effects is developed. The failure criterion correlates well with the experimental measurements reported by Hudspeth et al. for all three indenters. Modeling the experiments provides new insights into the tensile failure strain of high-performance ballistic fibers at extremely small gage lengths subject to transverse impact loading.

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Ackermann, J. A., and T. J. Kozik. "End Effects in Laminated Anisotropic Beams—Part II." Journal of Energy Resources Technology 117, no. 4 (December 1, 1995): 285–89. http://dx.doi.org/10.1115/1.2835425.

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An analytical method of examining the stress field near the edge of a simply supported, laminated beam was developed in Part I of this paper. The result was a system of second-order, ordinary, linear, nonhomogeneous differential equations. A numerical and analytical technique for solving these equations is presented in this paper. The method is a versatile stress analysis procedure which can accommodate any combination of material lay-up and can simulate any prescribed distribution of normal load on the upper and lower surfaces. The reactions at the ends of the beam may be distributed over the surface edges in a fashion most accurately characterizing the physical supports. An all-steel lay-up is examined as a basis for comparison with Bernoulli-Euler and Timoshenko theory; and a two-layered steel/aluminum beam is examined to simply demonstrate the method’s capability of determining the interlaminar transverse shear and normal stresses.

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Zarei, A., and A. Khosravifard. "A meshfree method for static and buckling analysis of shear deformable composite laminates considering continuity of interlaminar transverse shearing stresses." Composite Structures 209 (February 2019): 206–18. http://dx.doi.org/10.1016/j.compstruct.2018.10.077.

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Nikbakht, Masood, Hossein Hosseini Toudeshky, and Bijan Mohammadi. "Experimental validation of an empirical nonlinear shear failure model for laminated composite materials." Journal of Composite Materials 51, no. 16 (September 19, 2016): 2331–45. http://dx.doi.org/10.1177/0021998316669992.

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This paper aims to develop a numerical nonlinear progressive damage model for laminated composite materials considering in-plane and out-of-plane shear stresses in combination with cohesive interface elements to predict the structural response and the failure mechanisms of laminated composite materials. For this purpose, the constitutive models for intralaminar and interlaminar damage modes have been developed as a numerical code by a UMAT subroutine and implemented in commercial finite element software. This model, which is based on the continuum damage mechanics approach, enables to predict the gradual degradation of material properties with five distinct damage parameters for different failure modes; three of these damage factors apply the shear damage contribution as a separate damage mode by a separate damage factor into the model and characterize it by shear damage dissipation energy, and two parameters for fiber and matrix in transverse directions. Also, a series of experiments have been performed to characterize and validate the nonlinear behavior of glass/epoxy laminate. This model is used to predict the behavior and the final strength of open-hole tension specimens. A reasonably good agreement was also achieved between numerical predictions and experimental observations in terms of shapes, orientations and sizes of individual intraply damages induced around the notch and also the final strength of open-hole tension specimen.

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Araujo, Andreia, Diogo Vale, Panagiotis-Nektarios Pappas, Nikos Koutroumanis, and Raquel M. Santos. "Challenges and opportunities on nano-enabled multifunctional composites for aerostructures." MATEC Web of Conferences 304 (2019): 01007. http://dx.doi.org/10.1051/matecconf/201930401007.

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The incorporation of carbon-based nanomaterials in the polymeric matrix of carbon fibre reinforced polymer composites has recently received worldwide attention, aiming to enhance their performance and multifunctionality. In this work, different loadings of nanoparticles from the graphene family, including reduced graphene oxide (rGO) and graphene nanoplatelets (GNPs), were produced from graphite exfoliation. The mixing conditions for the production of epoxy-based suspensions were optimized using a three-roll mill, by changing the residence time and hydrodynamic shear stresses. The rheological behaviour, electrical conductivity and optical assessment were performed to study the influence of these nanoreinforcements on the resin properties. Afterwards, pristine and modified suspensions containing 0.089 wt. % of rGO or 2.14 wt. % of GNPs were used for manufacturing pre-impregnated materials with carbon fibre volume fractions of approximately 59 %. The nano-enabled CFRPs presented improved transverse electrical conductivity between 48 and 64 % when compared to the reference material. Significant enhancement of interlaminar fracture toughness (98.4 %) was found with GNPs.

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Gruttmann, Friedrich, and Werner Wagner. "Ein neues FE-Modell zur Berechnung von geschichteten Platten mit kontinuierlichen interlaminaren Schubspannungen/A new FE–model for the computation of layered plates with continuous interlaminar transverse shear stresses." Bauingenieur 91, no. 05 (2016): 179–87. http://dx.doi.org/10.37544/0005-6650-2016-05-39.

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In dieser Arbeit werden geschichtete Platten unter statischer Belastung betrachtet. Es wird ein Mehrfeldfunktional vorgeschlagen, dessen zugehörige Euler–Lagrange–Gleichungen neben dem Kräfte– und Momentengleichgewicht der Schnittgrößen lokale Gleichgewichtsbeziehungen in Spannungen liefert. Innerhalb eines finiten Plattenelements mit vier Knoten werden die Verwölbungen mit schichtweisen kubischen Ansatzfunktionen interpoliert. Dies hat zur Folge, dass die interlaminaren Schubspannungen automatisch kontinuierlich und die Spannungsrandbedingungen exakt erfüllt sind. Elimination der Wölb– und Lagrangeparameter auf Elementebene führt zu einem gemischt–hybriden Plattenelement mit fünf Freiheitsgraden an den Knoten. Damit können übliche Verschiebungsrandbedingungen angesetzt werden.

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Hou, T. H., and R. G. Bryant. "Processing and Properties of IM7/LARC™ -Si Polyimide Composites." High Performance Polymers 9, no. 4 (December 1997): 437–48. http://dx.doi.org/10.1088/0954-0083/9/4/007.

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LARC™-SI (NASA Langley Research Center-Soluble Imide) is an aromatic thermoplastic polyimide. LARC™-SI is synthesized from equimolar amounts of oxydiphthalic anhydride (ODPA), 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA) and the equivalent amount of 3, 4′-oxydianiline (3, 4′-ODA). Phthalic anhydride (PA) was used as an endcapper to control molecular weight. A 30% solid LARC™-SI solution (in NMP/Xylene: 9/1 v/v) with 3% stoichiometric imbalance was made into unidirectional long-fibre-reinforced prepregs. Thermal properties, volatile depletion behaviour and resin rheology were thoroughly characterized. Using this information, two composite moulding cycles were developed that consistently yielded well consolidated, void-free laminates. Composite mechanical properties such as short-beam shear strength, longitudinal and transverse flexural strength and flexural modulus, longitudinal tensile strength and notched and un-notched compression strengths, fracture toughness, open-hole compression strength and compression after impact (CAI) strength were measured at room temperature (RT) and elevated temperatures. LARC™-SI composite exhibited very good toughness and damage tolerance. The interlaminar fracture toughness and the CAI strength were measured at 1.72 kJ m−2 at 35.2 GPa respectively.

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Tomlinson, Scott M., and Roberto A. Lopez-Anido. "Scale and manufacturing effects on tensile strength of marine grade sandwich composite panel joints." Journal of Sandwich Structures & Materials 22, no. 6 (August 9, 2018): 1983–2008. http://dx.doi.org/10.1177/1099636218792676.

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In this article, scale and manufacturing effects on the tensile strength of marine grade sandwich composite panels and joints are investigated to aid in the fabrication of large modular ship hulls. This is done by researching transverse sandwich composite joint design, experimental tension methods, and scale and manufacturing effects on tensile strength. Three scales are utilized in this investigation of tension characteristics: coupon scale, table-top single panel fabrication scale, and in position mock-up full-size fabrication scale. First, material properties are gathered through industry standard coupon scale fabrication and testing. Next, a single-infusion baseline panel along with two ship hull transverse joint designs are chosen, fabricated, tested, and compared at single panel scale. These tests include individually fabricated hull panels, as well as secondary structural stiffener sandwich composite web panels, and stiffener flange components. The highest performing joint design is then utilized in a mock-up full-size fabrication scale structure. This structure includes both a transverse hull joint, as well as joints in the secondary structural stiffener web and flange. This mock-up fabrication scale component was then cut apart and tested in tension. The novel sandwich composite panel joint tension experimentation methods used indicate the methods studied are reliable for determination of characteristic tensile properties, and that the joints selected are effective. Investigations concerning scale effects comparing baseline fiber failure mode tension results from the coupon scale to the single panel scale, and manufacturing effects comparing joint interlaminar shear failure mode from the single panel scale to the mock-up fabrication scale, show decreased ultimate tensile strength with increased overall part size and manufacturing complexity. These factors, applied to a reference strength to achieve a nominal strength, were found to range from 0.796 to 0.846.

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Zhigun, V. I. "Experimental evaluation of the load-carrying capacity of composites with a circular hole when subjected to combined loading in interlaminar shear and transverse compression." Mechanics of Composite Materials 27, no. 1 (1991): 54–58. http://dx.doi.org/10.1007/bf00630719.

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Hou, T. H., N. J. Johnston, and T. L. St Clair. "IM7/LARCTM-IA polyimide composites." High Performance Polymers 7, no. 1 (February 1995): 105–24. http://dx.doi.org/10.1088/0954-0083/7/1/009.

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LARCTM-IA (Langley Research Center-Improved Adhesive) aromatic polyimide, based on oxydiphthalic anhydride and 3.4'-oxydianiline, was evaluated as a matrix for high-performance composites. Six poly(amide acid)solutions in N-methylpyrrolidone (NMP), end-capped with phthalic anhydride to various theoretical molecular weights, were synthesized and their molecular weights and molecular weight distributions determined, Importantly, high concentrations of low-molecular-weight species were found in all the offset compositions. Except for the 1% offset polymer, all fully imidized films failed a solvent resistance test which involved immersion in acetone, methyl ethyl ketone, toluene, dimethylacetamide and chloroform for 1 min followed by a fingernail crease. Unidirectional prepreg was fabricated from each of the six resins by both standard drum winding procedures and the LARC multipurpose prepreg machine. The consolidation cycle developed previously for IM7/LARCTM-ITPI composites was found to be equally applicable for IM7/LARCTM-IA composites since both materials are similar and were prepared in and prepregged from NMP. An optimal end-capped resin composition was identified (4% stoichiometric imbalance) by using, as a screening tool, initial composite mechanical properties (short-beam shear strength, longitudinal flexural strength and flexural modulus) at room temperature, 93, 150 and 177°C. Composite engineering properties for the 4% offset composition were obtained, including longitudinal tension, transverse flexural, longitudinal compression, interlaminar shear, short block compression, open hole compression and compression strength after impact. Notably, the CAI strength was 303.2 MPa (44 Ksi) showing that the LARCTM-IA composites have good damage tolerance. A minor modification of LARCTM-IA polymer backbone which did not alter the consolidation cycle, designated as LARCTM-IAX, improved solvent resistance measurably. Mechanical properties of IM7/LARCTM-IAX composites were shown to be comparable to those exhibited by the baseline IM7/LARCTM-IA composites.

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Chitturi, Sai Krishna, A. A. Shaikh, and Alpesh H. Makwana. "Static analysis of thermoset-thermoplastic-based hybrid composite." International Journal of Structural Integrity 11, no. 1 (August 7, 2019): 107–20. http://dx.doi.org/10.1108/ijsi-05-2019-0046.

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Purpose A growing response in the development of hybrid composites to conquer the deficiency of neat composites has provoked doing this work. Thermoplastic Polycarbonate material offers better impact toughness with low structural weight. There is a little/no information available over the selected sandwich hybrid composite prepared from woven E-Glass and polycarbonate sheet. The purpose of this paper is to understand the response of the novel hybrid structure under tensile, flexural, interlaminar shear and impact loading conditions. Design/methodology/approach The hand-layup technique is used for fabricating the hybrid composites in the laminate configuration. The hybrid composites are prepared with a total fiber content of 70 percent weight fractions. The effect of the percentage of reinforcement on mechanical properties is evaluated experimentally as per American society for testing materials standard test methods. The damaged mechanisms of failed samples and fractured surfaces are well analyzed using vision measuring system and scanning electron microscopy. Findings A decline in densities of hybrid composites up to 22.5 percent is noticed with reference to neat composite. An increase in impact toughness up to 40.73 percent is marked for hybrid laminates owing to the ductile nature of PC. Delamination is identified to be the major mode of failure apart from fiber fracture/pull-out, matrix cracking in all the static loading conditions. Originality/value The response of novel hybrid composite reported has been explored for the first time in this paper. The outcome of experimental work revealed that hybridization offered lightweight structures with improved transverse impact toughness as compared to conventional composite.

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Journal articles on the topic 'Interlaminar transverse shear'

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