热塑性复合材料层合板的层间应力与损伤机理

Interlaminar stress and damage mechanism of thermoplastic composite laminates

使用有限元生成软件FEPG和表征热塑性复合材料AS4/PEEK非线性行为和应变率相关行为的三维粘塑性模型,计算了复合材料角铺设层合板在单向拉伸时的界面层间应力.层间应力的三维分布图表明,AS4/PEEK对称角铺设层合板的层间剪应力在自由边缘处存在很明显的自由边缘效应;层间正应力也存在自由边缘效应,对于轴向拉伸,其在自由边缘处的值为负.随着铺设角的增大,自由边缘处二者的值均减小.层间应力存在端头效应,甚至比边缘效应还明显.随着铺设角的增大,层间应力在两端头处的值降低,层间正应力由压应力变为拉应力.主要由纤维控制的角铺设AS4/PEEK层合板,在自由边缘处较大的层间剪应力是引起其层间分层的主要原因;主要由基体控制的角铺设AS4/PEEK层合板,其首先产生的是面内应力破坏,而不是层间分层.

The three-dimensional viscoplasticity model for characterizing the nonlinear behavior and the strain rate dependence behavior of the thermoplastic composites AS4/PEEK was realized by developing the relative procedure. The interlaminar stresses of the angle-ply laminates under uniaxial tension were calculated. The results show that the interlaminar shear stresses of the AS4/PEEK angle-ply laminates exist distant edge-effects; The interlaminar normal stresses also have edge-effects which are negative at the free edges for uniaxial tension. With increasing the ply angle, both the above interlaminar stresses decrease. For the interlaminar stresses there exist end-effects which are even stronger than the edge-effects. Moreover, the values of the above interlaminar stresses at the two ends both decrease and the normal stresses at this location change from compress stresses to tensile stresses. For the fiber-dominated angle-ply AS4/PEEK laminates the large interlaminar shear stresses in the free edges lead to the delamination, while for the matrix-dominated laminates, they should first produce in-plane damages but not delamination.