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Effect of Dynamics Parameters on Low-Velocity Impact Damage in Composite Laminates

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Tutor: WangHai YuZheFeng
School: Shanghai Jiaotong University
Course: Aircraft design
Keywords: laminated composite plate,low-velocity impact,damage,scale effect,dynamics param
Type: Master's thesis
Year:  2012
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Composite materials are widely used in aerospace, automobile and new energy mainly due to their high specific strength, high specific modulus and strong designable characteristic. However, impact resistance of composite materials is so weak that their future application and development are severely obstructed, and especially the low-velocity impact damage is seriously threatening the carrying ability of composite structures. Therefore, it is very meaningful to study and predict damage in composite structures subjected to low-velocity impact.The objective of the thesis is to investigate damage characteristics of laminated composite plate due to low-velocity impact. Firstly, a fully 3-D composite laminate model is developed using finite element analysis software ABAQUS. The model accounts for all forms of damage such as fibre failure, matrix cracking, matrix crushing and delamination. In the model, in-plane damage is simulated by solid elements, delamination is predicted using cohesive elements. Material properties are degraded through the user subroutine VUMAT once impact damage initiated. Impact damages in laminated composite plates are simulated via 3-D composite model and VUMAT, and the results agree with experimental results.Secondly, the above simulation method is used to investigate scale effect on the responses of laminated composite plate subjected to low-velocity impact. Based on scaling laws, three full 3-D composite laminate models of different scales are developed using ABAQUS finite element code. Impact responses under different impact velocities are investigated. Some conclusions are obtained: If no damage occurs in the composite laminates during the impact, the impact time and the contact force are consistent with the presented scaling rules; Whereas, the impact time and the contact force are not agree with the scaling rules well once the impact damage generated; Moreover, if the velocity ratios between each models are equal to the square root of their scale factor, the relative delamination dimensions in the models are nearly the same, which is in accordance with the experimental results. Further investigation shows that the dimensions of in-plane damage, i.e., fibre failure, matrix cracking and matrix crushing, can not be predicted using the above rules.Thirdly, the impact response of laminated composite plate is influenced by span and the impactor-plate mass ratio. Concerning to the impact problem of composite laminated plate with the variable length and width but a constant stacking squence, a FEM method is used to investigate the effect of span on the responses and damage of composite laminates impacted by intermediate-mass impactor and large-mass impactor.Finally, the numerical method is used to study the effect of dynamics parameters, i.e., impactor mass and impact velocity, on the responses and damage of laminated composite plate, especially, the effect of impactor mass on the responses and damage of laminated composite plate is investigated as the impact energy is equal.
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