基于连续介质损伤力学的复合材料层合板低速冲击损伤模型

基于连续介质损伤力学（CDM）方法，建立了分析复合材料层合板低速冲击问题的三维数值模型。该模型考虑了层内损伤（纤维和基体损伤）、层间分层损伤和剪切非线性行为，采用最大应变失效准则预测纤维损伤的萌生，双线性损伤本构模型表征纤维损伤演化，基于物理失效机制的三维Puck准则判断基体损伤的起始，根据断裂面内等效应变建立混合模式下基体损伤扩展准则。横向基体拉伸强度和面内剪切强度采用基于断裂力学假设的就地强度（in-situ strength）。纤维和基体损伤本构关系中引入单元特征长度，有效降低模型对网格密度的依赖性。层间分层损伤情况由内聚力单元（cohesive element）预测，以二次应力准则为分层损伤的起始准则，B-K准则表征分层损伤演化。分别通过数值分析方法和试验研究方法对复合材料典型铺层层合板四级能量低速冲击下的冲击损伤和冲击响应规律进行分析，数值计算和试验测量的接触力-时间曲线、分层损伤的形状和面积较好吻合，表明该模型能够准确地预测层合板低速冲击损伤和冲击响应。

A model for low velocity impact damage analysis of compositelaminates based on continuum damage mechanics

A novel three-dimensional composite damage model based on continuum damage mechanics (CDM) was developed to investigate low-velocity impact behavior of composite laminates. The maximum strain failure criterion was used to predict the initiation of fiber damage and the fiber damage revolution was evaluated by a bi-linear damage constitutive relation. A physically-based failure theory and three dimensional Puck criterion was employed to capture the onset of matrix damage and the damage evolution was determined by the effective strain on the fracture plane under the particular fracture angle. The in-situ strength of transverse tensile and in-plane shear depended on the assumption of fracture mechanics. The mesh dependency was alleviated effectively by introducing the characteristic length of element in the constitutive model of fiber and matrix damage. The interlaminar delamination damage was simulated by the cohesive element. Quadratic stress criterion and B-K power law was adopted to confirm the damage initiation and damage revolution for the interface element respectively. The impact damage and impact responses of composite laminates under four levels of impact energy were studied by experimental and numerical method. The agreement between the simulation results and experimental results about impact-force curves, delamination shape and size shows that the finite element analysis model can effectively predict the impact responses and impact damage.