Effect of fiber angle orientation and stacking sequence on mixed mode fracture toughness of carbon fiber reinforced plastics: Numerical and experimental investigations

Abstract

This paper focuses on the effect of fiber orientation and stacking sequence on the progressive mixed mode delamination failure in composite laminates using fracture experiments and finite element (FE) simulations. Every laminate is modelled numerically combining damageable layers with defined fiber orientations and cohesive zone interface elements, subjected to mixed mode bending. The numerical simulations are then calibrated and validated through experiments, conducted following standardized mixed mode delamination tests. The numerical model is able to successfully capture the experimentally observed effects of fiber angle orientations and variable stacking sequences on the global load-displacement response and mixed mode inter-laminar fracture toughness of the various laminates. For better understanding of the failure mechanism, fracture surfaces of laminates with different stacking sequences are also studied using scanning electron microscopy (SEM).

Mixed-Mode Delamination Failures of Quasi-Isotropic Quasi- Homogeneous Carbon/Epoxy Laminated Composite

“…Nevertheless, the shear cusps in the MMF specimen were less significant and more random compared to the ENF specimen, which was similar to the observation by Naghipour et al [6]. In addition, the roughness of the MMF specimen was less than the ENF specimen [7]. On the other hand, matrix cracking seemed to be another major failure mechanism.…”

“…However, significant shear cusps were observed on the 0 l a y e ri nt h e4 5 direction, which was attributed to the shear mode loading. It has also been reported that the high shear mode would draw large shear cusps [6,7]. A certain amount of matrix cracking was observed on the 45 layer, which was believed to be due to the interaction between 0 and 45 layers during shearing.…”

“…In addition, in the use of laminated composites, multidirectional laminates have been generally known to have higher interlaminar fracture toughness compared to the unidirectional laminates [6,7]. This could be attributed to relatively blunt crack tip or intralaminar crack [7].…”

“…This could be attributed to relatively blunt crack tip or intralaminar crack [7]. To study the delamination behaviour of multidirectional laminates, characterisation was commonly conducted on pure mode I, pure mode II and mixed-mode I+II tests [4,8,9].…”

Investigation of delamination and damage due to free edge effects in composite laminates using cohesive interface elements

“…0.32 3.45 6 10.3 127.6 Table 3 The strength properties of the unidirectional laminate made of AS4/APC2 (PEEK) (Naghipour et al, 2010) where 1 and x denote the fiber direction while 2 and y represent for the matrix direction. Moreover, the subscript T is representing for the tension and C for the compression properties of the laminate.…”