材料期刊网

建立了一种新的有限元三维模型，对准各向同性纤维增强复合材料层合板[45/0/-45/90]s 和[45/-45/90/0]s 进行了开孔拉伸的破坏模拟。每一层均采用三维实体单元(ABAQUS中的 C3D8R 单元)，由于基体比纤维强度低，在很低的拉伸载荷下，圆孔周围基体受到剪切力会出现沿纤维方向的纵向劈裂或基体开裂，从而钝化圆孔，大大减小应力集中，提高材料承载能力。为了准确模拟层合板的破坏，在每层圆孔周围(90°层除外)沿纤维方向引入2组基于表面的内聚力接触来模拟层内纵向劈裂，同时用这种接触来模拟层间的分层特性。为了提高计算效率并且保证计算精度，在圆孔周围采用精细的网格，其余地方采用相对稀疏的网格。在内聚区保证足够的单元个数，这样既能准确刻画内聚区应力分布，又能缓解网格依赖性。与文献中实验结果的对照显示，取得了较好的一致性。

A new 3D finite element model was established,which had been used to simulate the open-hole tensile damage of quasi-isotropic fiber-reinforced composite laminates with stacking sequences of [45/0/-45/90]s and [45/-45/90/0]s .Each ply was modeled by 3D solid elements (C3D8R in ABAQUS notation).Because the matrix con-stituent is much weaker than the fiber,longitudinal splitting or matrix cracking may take place at a very low tensile load due to the local shear force near the hole edge.The longitudinal splitting can blunt the hole and alleviate the stress concentration.And the load-carrying capacity of the material will be enhanced.In order to accurately simulate the damage of the laminates,two surface-based cohesive contacts had been inserted tangential to the hole along the fiber direction in each ply (except for the 90°ply)to simulate the intra-ply longitudinal splitting.Meanwhile,sur-faced-based cohesive contacts had also been used to simulate the inter-ply delamination characteristic.In order to im-prove the computation efficiency and guarantee the calculation accuracy,fine mesh had been used within the region around the hole and relative coarse mesh in other regions.Within the cohesive zone,a certain number of elements was ensured,so that we can both accurately capture the stress distribution and alleviate the mesh dependency.When compared with experimental data in published literature,a good agreement is achieved.