Interlaminar stress and damage mechanism of thermoplastic composite laminates

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.