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A D Brown - One of the best experts on this subject based on the ideXlab platform.
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impact behaviour of pultruded gfrp composites under low velocity impact loading
Composite Structures, 2017Co-Authors: Amar Khennane, P J Hazell, A D BrownAbstract:Abstract 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 67 J. 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.
Zhoulian Zheng - One of the best experts on this subject based on the ideXlab platform.
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general perturbation solution of large Deflection circular plate with different moduli in tension and compression under various edge conditions
International Journal of Non-linear Mechanics, 2013Co-Authors: Xiaoting He, Qiang Chen, Zhixiang Wang, Zhoulian ZhengAbstract:Abstract The large Deflection problem for a thin circular plate with different moduli in tension and compression has dually non-linear characteristics. In this paper, we use perturbation technique to obtain a general analytical solution of thin circular plate with different moduli in tension and compression, in which four edge conditions including rigidly clamped, clamped but free to slip, simply hinged and simply supported are considered. Because the perturbation solution is expanded in ascending powers of a known perturbation parameter (Central Deflection, for example) and the unknown constants and functions in the solution are gradually determined by decomposing boundary conditions and governing equation, the constants and functions obtained in such a manner have an inherent consistency concerning material properties. The results show that via construction of some parameters reflecting materials properties, not only the solution based on bimodular elasticity theory may regress to that on classical theory with singular modulus, but also the solution obtained under simply hinged edge may serve as a general solution to describe other three edge conditions. Via the general solution, the relations of load vs. Central Deflection, the plate–membrane transition for bimodular problem and the radial membrane stresses and bending stresses at the center and edge of the plate, are also discussed. Moreover, the comparison between the analytical solutions and numerical results indicates that the perturbation solutions based on the Central Deflection are overall valid. This work will be helpful for analyzing the mechanical behaviors of flexible layer structures while considering large deformation and bimodular effect.
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large Deflection axisymmetric deformation of circular clamped plates with different moduli in tension and compression
International Journal of Mechanical Sciences, 2012Co-Authors: Qiang Chen, Junyi Sun, Zhoulian ZhengAbstract:Abstract Ambartsumyan's bimodular model for isotropic materials deals with the principal stress state in a point, which is particularly useful in the analysis and design of structures. In this paper, based on the known flexural stiffness for a bimodular thin plate in small-Deflection bending, we establish the von Karman equations with different moduli in tension and compression and then use the perturbation method and the displacement variation method to solve the problem, respectively. The comparison shows that the perturbation solution based on the Central Deflection is valid. The analytical result shows that the bimodularity of the material will have an effect on the relation of load vs. Deflection to a certain extent. We also investigate the yield conditions for a bimodular thin plate in large-Deflection bending. It is concluded that this introduction of materials nonlinearity will eventually influence the yield stress at the edge and center of the plate, however, it does not change the yield order that when loading further, the edge of the plate will firstly yield and then the center of the plate. Moreover, during the transition from plate to membrane, the bimodular plate will gradually regress to the classical one. This work will be helpful for analyzing the mechanical behaviors of thin film materials with obvious bimodularity and with moderate thickness or hardness.
Lorenzo Iannucci - One of the best experts on this subject based on the ideXlab platform.
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Effect of fibre orientation on the low velocity impact response of thin Dyneema® composite laminates
International Journal of Impact Engineering, 2017Co-Authors: Mark K. Hazzard, Stephen R. Hallett, P.t. Curtis, Lorenzo IannucciAbstract:Abstract Ultra-high molecular weight polyethylene (UHMWPE) fibre reinforced composite materials are widely used in ballistic impact and collision scenarios due to their extremely high specific strength and stiffness. Exceptional levels of protection are provided by controlling the damage and deformation mechanisms over several length scales. In this study, the role of UHMWPE fibre architecture (cross-ply, quasi-isotropic and rotational “helicoidal” layups) is considered on the damage and deformation mechanisms arising from low velocity impacts with 150 J impact energy and clamped boundary conditions. Dyneema ® panels approximately 2.2 mm thick were impacted with a fully instrumented hemi-spherical impactor at velocities of 3.38 m/s. Full field deformation of the panels was captured through digital image correlation (DIC). The results indicate that the cross-ply laminate [0°/90°] had the largest back face Deflection, whilst quasi-isotropic architectures restricted and reduced the Central Deflection by an average of 43%. In the case of the [0°/90°] panel, the deformation mechanisms were dominated by large amounts of in-plane shear with limited load transfer from primary fibres. Conversely, the failure of the quasi-isotropic panels were dominated by large amounts of panel buckling over various length scales. The observed mechanisms of deformation with increasing length scale were; through thickness fibre compression, fibre micro-buckling, fibre re-orientation with large matrix deformation, lamina kink band formation, and laminate buckling. The helicoidal panels showed that bend-twist and extension-twist coupling were important factors in controlling clamped boundary conditions and the laminate buckling/wrinkling shape. Further examination of the impact zone indicated that the damage mechanisms appear to be fibre orientation dependent, with quasi-isotropic laminates having up to 37.5% smaller impact damage zones compared with [0°/90°]. The experimental observations highlight the importance of fibre orientation in controlling the deformation mechanisms under dynamic impact, in particular limiting the shear deformation of Dyneema ® panels.
Amar Khennane - One of the best experts on this subject based on the ideXlab platform.
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impact behaviour of pultruded gfrp composites under low velocity impact loading
Composite Structures, 2017Co-Authors: Amar Khennane, P J Hazell, A D BrownAbstract:Abstract 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 67 J. 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.
Said Kenai - One of the best experts on this subject based on the ideXlab platform.
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effects of reinforcement configuration and sustained load on the behaviour of reinforced concrete beams affected by reinforcing steel corrosion
Cement & Concrete Composites, 2012Co-Authors: L Hariche, Y Ballim, M Bouhicha, Said KenaiAbstract:Abstract Corrosion of reinforcing steel bars in concrete is one of the main causes of early deterioration and reduction of service life of reinforced concrete (RC) structures. This paper reports on the results of an experimental programme that was carried out to study the effect of reinforcement corrosion on the serviceability behaviour of RC beams under load. The main parameters investigated were the effects of reinforcement arrangement and the magnitude of the sustained load. Four series of scaled beams were tested, each series containing six beams, three of which were subjected to reinforcement corrosion while the other three were used as un-corroded control beams. All these beams carried the same sustained load during the process of reinforcement corrosion. The reinforcement arrangement for the fourth test series was identical to the first series but these beams carried a higher sustained test load. All the beams were subjected to a four-point bending load arrangement. Corrosion of the tension reinforcement was accelerated using an impressed current while the soffits of the beams were immersed in a 3% sodium chloride solution. The evolution of reinforcement corrosion and Central Deflection under simultaneous load and corrosion is given. The Deflections of the beams increase with progressive corrosion of the reinforcement especially during the early stages of corrosion as a result of propagation of transverse cracks and the expansive stresses induced by the corrosion products. The importance of the arrangement of the steel in the section of concrete on the performance in terms of Deflection was also clarified.