Multiscale modeling of the effect of sub-ply voids on the failure of composite materials

Abstract

A multiscale fracture model is developed to study the influence of defects appearing at a microscale in a fiber-reinforced composite laminate. The model establishes a link between the geometrical characteristics of sub-ply imperfections that may be created during manufacturing and the overall fracture strength and fracture energy of the composite. In particular, a recently-developed multiscale theory is expanded to account for microvoids inside the matrix and gaps between closely-spaced fibers that prevent filling. These defects are explicitly incorporated in finite element simulations to study their influence on the onset and propagation of cracks at the sub-ply level. To connect these microcracks to the effective fracture behavior at a ply-level, a computational homogenization technique is applied to extract the energeticallyequivalent macroscopic fracture properties. Through a parametric analysis of configurations, the influence of the void content (porosity), void type and void shape on the effective fracture strength and the effective fracture energy of a composite are quantified. Results show that the porosity is the main parameter influencing fracture properties while the shape of the defects and their type (matrix or interfiber) only play a secondary role. Furthermore, the influence of voids on the fracture properties appears to be strongly dependent on the loading conditions. In particular, for the range of porosity analyzed (up to 8%), the influence of voids in mode I on the transverse fracture strength is not significant but the transverse fracture energy decreases approximately linearly down to about 50% of its original value. In contrast, in mode II, the transverse fracture strength is significantly affected with increasing porosity. Furthermore, the transverse fracture energy depends nonlinearly on the porosity and the reduction is relatively more pronounced than for mode I.

Effect of Resin-Missing Defects on Tensile Behavior of Carbon Fiber/Epoxy Composites

“…Studying the effect of mesoscopic and microscopic defects on the mechanical properties of composites using experimental methods is challenging due to the difficulty in controlling the defects quantitatively [22]. As a result, most existing research has employed multiscale simulation methods to investigate this issue [23]. Dong et al [24] investigated the effect of mesoscopic void and microscopic void defects on the elastic properties of composites using a two-scale approach.…”

Averaging techniques for microstructures with localization bands due to damage progression

“…More recently, this failure zone averaging scheme has been investigated in terms of computational aspects [16] and applied within an FE2-analysis for concrete [17]. Moreover, the method has been successfully applied to microscopical cracks and debonding between matrix and fibers using cohesive zone elements [18][19][20][21].…”

Stochastic modelling of continuous glass-fibre reinforced plastics–considering material uncertainty in microscale simulations

“…He 7 developed an approach based on the geometrical representation of sub-ply voids in unidirectional unit cells and predicted the loading-dependent drop of the material strength at increasing void contents. Using similar modelling techniques, Chu, 8 Hyde 9 and Turteltaub 10 simulated the detrimental effect of void content and void shape on the material’s stiffness, strength and energy release rates respectively. The modelling of the voids has been differently handled by Liu in, 11 where elements were randomly deleted at the beginning of simulation.…”