Three-Dimensional Analysis of the Effect of Material Randomness on the Damage Behaviour of CFRP Laminates with Stochastic Cohesive-Zone Elements

Abstract

This raises the question of whether the inherent stochasticity of localised damage is of significance in terms of the global properties and design methods for such materials. This paper presents the numerical modelling based analysis of the effect of material randomness on delamination damage in CFRP materials by the implementation of stochastic cohesive-zone model (CZM) within the framework of the finite-element (FE) method. The initiation and propagation of delamination in a unidirectional CFRP double-cantilever beam (DCB) specimen loaded under mode-I was analyzed, accounting for the inherent microstructural stochasticity exhibited by such laminates via the stochastic CZM. Various statistical realizations for a half-scatter of 50% of fracture energy were performed, with probability a distribution based on Weibull's two-parameter probability density function. The damaged area and the crack lengths in laminates were analyzed, and the results showed higher values of those parameters for random realizations compared to the uniform case for the same levels of applied displacement. This indicates that deterministic analysis of composites using average properties may be non-conservative and a method based on probability may be more appropriate.

Micromechanical analysis of stochastic fiber/matrix interface strength effect on transverse tensile property of fiber reinforced composites

“…When investigating the stochastic fracture toughness effect on the delamination process of a DCB specimen, Ashcroft et al assumed the initial stiffness and fracture toughness to be proportional to the interface strength. [14][15][16][17] Similar approach was adopted in the present work (Figure 5), and the critical and failure separation of the cohesive interface were taken as 0 ¼ 10 À9 m and f ¼ 2 Â 10 À7 m (the two values were chosen by consulting parameter dimension in the literatures 7,9,10 ), respectively. To promote the solution convergence, a viscosity coefficient of 2 Â 10 À4 taken from O'Dwyer et al 7 was used.…”

“…Failure process of materials with stochastic local property is significantly different from that of identical cases. Ashcroft et al [14][15][16][17] investigated the random fracture toughness effect on the delamination process of a double cantilever beam (DCB) specimen with stochastic cohesive element and concluded that the microstructural randomness could significantly affect the macroscopic delamination process of composites.…”

How variability in interfacial properties results in tougher bonded composite joints by triggering bridging

“…Of course, variability in bonding properties might also be attributed to inherent surface defects in pregreg due to the fabrication process. Several studies have focused on the overall mechanical response of materials ( Dimas et al, 2016( Dimas et al, , 2015( Dimas et al, , 2014 or interface ( Taleb Ali et al, 2018;Xu et al, 2014;Motamedi et al, 2013;Khokhar et al, 2009Khokhar et al, , 2013Jumel, 2017 ) subjected to propertys heterogeneity induced by cracks, defects, or other types of flaws, and it was found that the material or bonding strengths are sensitive to randomly distributed properties.…”