Deducing the R-curve for trans-laminar fracture from a virtual Over-height Compact Tension (OCT) test

Abstract

The R-curve for Mode I trans-laminar fracture energy in quasi-isotropic IM7/8552 carbon/epoxy laminates is here deduced numerically from a virtual Over-height Compact Tension (OCT) test. A High-fidelity Finite Element Method (Hi-FEM) using the explicit Finite Element (FE) software LS-Dyna was adopted. Cohesive interface elements and a Weibull fibre failure criterion were used to predict failure. The input parameters for the Hi-FEM were measured from independent characterisation tests.OCT specimens were tested to verify the Hi-FEM results with good agreement. The Rcurve effect is postulated to be caused by the growth of the height of the Fracture Process Zone (FPZ) with crack length. Hi-FEM can be used to better understand Mode I trans-laminar fracture toughness tests and generate fracture properties such as damage heights and R-curves for future structural scale models.

Virtual characterization of nonlocal continuum damage model parameters using a high fidelity finite element model

“…The OCT [23,28] geometry produces stable and self-similar crack growth in dispersed quasi-isotropic CFRP laminates. A FE mesh was created based on a unit cell, which can accommodate potential splitting in different fibre directions [5].…”

“…Inserted cohesive interface elements were therefore pre-defined to simulate potential intra-laminar matrix splitting, and the laminae were connected with cohesive interface elements to simulate delamination. Further to the previous study [4], a High-fidelity Finite Element Method (Hi-FEM) has been developed to numerically predict the R-curve for Mode I trans-laminar fracture toughness [5]. Beyond the FPZ development in [4], the pre-defined potential paths for multiple splits were extended over the entire crack path.…”

“…Initially, the R-curve for Mode I trans-laminar fracture was determined based on the effective crack length which includes the FPZ. An alternative definition of R-curve was also discussed based on the 'true' crack length which excludes the FPZ [5].…”

“…In this paper, we present a virtual material characterization strategy to determine the key parameters of the continuum damage model, CODAM2, using the High-fidelity Finite Element Method (Hi-FEM) [5] effectively as the virtual testing tool. This will enable physics-based progressive damage simulation of large scale composite structures that are required, for example, in aerospace or automotive applications.…”

“…Here, we propose a solely virtual characterization of ply-based CODAM2 parameters to simulate damage progression on the basis of the validated Hi-FEM model [5]. This methodology is applicable to arbitrary loading conditions.…”