Mechanical Analysis Of Bending Interlaminar Macro-micro Nonlinear Behavior Of Thermoplastic Composite Laminates

Delamination is one of the important damage reasons of thermoplastic composite laminates AS4/PEEK. To evaluate its structure inactivation and damage, it is essential to do quantitative analysis to the interlaminar stresses, strains and displacements and free edge effects under bending load.Based on the one-parameter elastoplastic constitutive relationship of C.T.Sun et al, a corresponding finite element format is deduced, and a user subroutine is written in ABAQUS. Under bending load, several finite element models of [0/90]3s,[±25]s4 and [0/±45/90]2s composite laminates are developed; interlaminar stresses, strains and displacements and free edge effects are analyzed; and the distributions of interlaminar stresses, strains and displacements along length direction x,width direction z and thickness direction y are also supplied. The results indicate that, interlaminar shear stresses breakout is an important reason of delamination for [±25]s4 laminates, and free edge stress centralization is obvious to all the laminates within both tensile and compress edges.Utilizing submodel technology, this paper establishes micro interlaminar elastoplastic submodel which contains fibre-matrix two materials, and analyze the influence of free edge delamination to the stresses distribution of fibre-matrix interface in region of geometrical interlaminar. It shows that, in the geometrical interlaminar interfaces, the stresses are larger near to the interfaces between fibres and matrix. Free edges affect interlaminar stresses distribution intensively in half fibrous diameter areas near to free surfaces. The more the fibres close with the geometrical interlaminar interface, the larger of the stresses near to the interfaces between fibres and matrix.