复合材料层合板低速冲击损伤分析的连续介质损伤力学模型
CONTINUUM DAMAGE MECHANICS MODEL FOR LOW-VELOCITY IMPACT DAMAGE ANALYSIS OF COMPOSITE LAMINATES
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摘要: 针对复合材料层合板低速冲击损伤问题,提出了一种各向异性材料连续介质损伤力学模型,模型涵盖损伤表征、损伤起始判定和损伤演化法则3 个方面. 通过材料断裂面坐标下的损伤状态变量矩阵完成损伤表征,并考虑断裂面角度的影响,建立了主轴坐标系下的材料损伤本构关系. 损伤起始由卜克(Puck) 失效准则预测,损伤演化由断裂面上的等效应变控制,服从基于材料应变能释放的线性软化行为. 模型区分了纤维损伤和基体损伤,并根据冲击载荷下层内产生多条基体裂纹继而扩展至界面形成层间裂纹(分层) 的试验观察,引入基体裂纹饱和密度参数表征层间分层. 以03/45/-45S 和45/0/-45/904S 两种铺层的复合材料层合板为例,预测了不同冲击能量下复合材料层合板的低速冲击损伤响应参数,试验结果证明了连续介质损伤力学模型的有效性.模型在不同网格密度下的计算结果表明单元特征长度的引入可以在一定程度上降低损伤演化阶段对网格密度的依赖性.Abstract: A three-dimensional anisotropic continuum damage mechanics (CDM) model, including damage characterization, damage initiation criterion and damage evolution law, was presented to analyze low-velocity impact damage of composite laminates. With considering affects of the fracture plane angle, material constitutive relation of damage states in the fracture plane coordinates was established by introducing damage state variable matrix in the material principal coordinates. The onset of damage was evaluated by the Puck criterion and the evolution of damage was controlled by equivalent strain on the fracture plane. Based on the viewpoint of strain energy release, the material was assumed to exhibit linear strain-softening behavior. Fiber fracture (FF) and inter-fiber fracture (IFF) were simulated within the lamina. Due to the experimental evidence which indicated that multiple intralaminar cracks developed in a composite laminate and coalesced in to one interface crack (delamination) under impact load, a intralaminar matrix crack density parameter at saturation was introduced to scale interlaminar delamination. The relevant low velocity damage response parameters of the laminates 03/45/-45S and 45/0/-45/904S were predicted with the proposed model at various impact energies. A good agreement was achieved with experimentally obtained data and showed the validity of CDM model in this paper. Furthermore, results for different mesh-densities indicated that the approach by introducing a characteristic length of the element could alleviate the mesh dependency at the stage of material damage evolution.