Micromechanical investigation of cross-ply carbon composite laminates with glass microtubes using CZM and XFEM

Transverse cracking and delamination are two of the most common failure modes in cross-ply composite laminates. The initiation and combination of these two failure mechanisms lead to catastrophic failure modes in composite structures. This paper investigates the impact of the layer thickness and the presence of microtubes on the in situ strength of the 90° layer, the influence of induced delamination on the strength of [0/90 _n /0] laminates in micro and macro scales is also investigated. In order to model the fiber–matrix debonding and matrix cracking formation in 90° plies, the cohesive zone model and extended finite element method (XFEM) are used. Afterward, to examine the induced delamination formation which originates from the tips of the transverse cracks, cohesive surfaces are placed between adjacent layers. It was shown that by increasing the thickness of a 90° layer, both the strength of the first transverse crack formation and the stress for delamination initiation decrease. On the other hand, the presence of microtubes in the vicinity of the 90° and 0° interfaces leads to an increase in the strength of the 90° ply and postpones delamination initiation.