层合板层间断裂分析的组合界面单元及其特性

提出了一种由刚性元和零厚度的内聚力单元组合而成的新型界面单元,该界面单元嵌在板壳结构界面之间,可用来模拟界面损伤的起始和演化,能考虑板壳的平动和转动对分层损伤的作用。该界面单元具有有限厚度,八个结点,每个结点有五个自由度,通过刚性元将板壳单元结点的位移和结点力转换到内部零厚度的内聚力单元上,界面损伤通过内聚力单元的损伤演化体现出来。采用板壳单元和新型界面单元建立有限元模型,对混合弯曲(MMB)试验和双悬臂梁(DCB)弯曲试验进行了计算模拟,计算结果能很好地模拟结构的界面损伤过程。相比传统的用内聚力单元和三维实体单元组成的模型,建模方便,在精度相当的前提下,可以使单元尺寸增大一倍,减少裂尖内聚力区域(cohesive zone)内的单元数量,缩小计算规模,提高计算效率。

Characterization of a combined interfacial element for laminated composites

A new interfacial element composed of a zero thickness cohesive element and eight rigid elements was introduced. Such interfacial elements were placed at the interface of shell structures to model the initiation and growth of delamination along the interface. The translational and rotational nodal movements of the adjacent shell element contributed to the deformation of the cohesive element. The type of the interfacial element was of finite thickness and eight-nodes, each of them possessed five degrees of freedom for coping with the corresponding shell element node. The rigid elements transfered nodal displacements and forces of the shell elements to the zero-thickness cohesive element by which the interlaminar damages were exhibited. The mixed mode bending (MMB) and double cantilever beam (DCB) bending tests were simulated by the shell and proposed elements, and the results agree pretty well with the experiments. Comparing with the traditional model of solid elements connected by cohesive elements, shell elements coupled with the suggested interfacial elements are easier to be used for the sheet-like or laminated structures with internal interfaces. The latter allows larger element size in the cohesive zone, reducing the total model scale and enhancing the computational efficiency.