The effect of voids on matrix cracking in composite laminates as revealed by combined computations at the micro- and meso-scales

Abstract

Voids are an important type of manufacturing defects in fiber-reinforced composites. Matrix cracking is sensitive to the presence of voids. Although this cracking occurs at the ply scale, its dynamics is strongly affected by ply's microstructure, in particular, fiber distribution, fiber content, and the presence of voids. In the current study, a computational approach to simulate the influence of intra-laminar voids on cracking in composite laminates is developed. The approach combines finite element models of two scales: a micro-scale model, where the fibers and voids are modeled explicitly, and a meso-scale model, where the cracking phenomenon is captured on the ply scale. The micro-scale model, incorporating plasticity and damage in the matrix, provides input for the meso-scale model, which simulates the progressive cracking by means of the extended finite element method. The methodology is applied to investigate the effect of voids on the density of transverse cracks in cross-ply laminates in function of the quasi-static tensile load. Different sizes and contents of voids, which are chosen based on experimental micro-computed tomography data, are simulated. The numerical experiments show that the presence of voids leads to earlier start of the cracking, with the crack density evolution less sensitive to voids.

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance

“…Mehdikhani et al 278 also studied the effect of voids on transverse cracks by means of a numerical approach combining the micro-and meso-scales. Using computational micromechanics, they calculated the stiffness, strength, and fracture toughness, degraded by voids, and used these parameters as input for a ply-level model, based on extended FE method.…”

“…For simulation of the effect of voids on transverse cracking, Mehdikhani et al 278 developed a combinedscale approach. At the micro-scale, a single void was modeled among hundreds of fibers randomly distributed in a 3D RVE with small thickness.…”

Detailed characterization of voids in multidirectional carbon fiber/epoxy composite laminates using X-ray micro-computed tomography

“…Damage development with regard to the defects in this material was studied in [32,35], where the effect of voids on matrix cracking evolution in cross-ply laminates was experimentally and numerically investigated.…”

“…The creation of such a dataset is of great importance, especially for modeling studies investigating the effect voids have on the mechanical behavior of carbon FRCs . In fact, the idea of the current study was born when the authors were conducting a simulation study on the effect of voids on ply cracking evolution [32]. In order to build realistic models, the authors required a dataset containing the statistical distribution of void characteristics.…”

Fibre Alignment and Void Assessment in Thermoplastic Carbon Fibre Reinforced Polymers Manufactured by Automated Tape Placement

“…The first observation is the amount of voids that appears in IM7/PEEK and AS4/PA12. This method could also be used for the void content measurements [ 44 ], but, due to the high cost and limited sample size, the authors decided to proceed with the data from the optical microscopy. This observation is correlated to the lower volume fraction obtained for both of the thermoset-based composites.…”