Abstract

Open hole tension (OHT) and 4-point bending (4PB) tests are some of the standard qualification tests at coupon level in the aerospace industry. To minimize the number of tests and associated time and cost, it is essential to predict the failure strength using finite element models. In this context, current paper discusses the analysis and simulation methodology that was used to study OHT and 4PB specimens made of carbon/epoxy 2D woven plies. The approach is based on specific meso-models available in the literature (Ladeveze type models) for modeling intra and inter-laminar behaviors of woven plies laminates. The intra-laminar model can represent fiber failure, progressive damage in the matrix (cracks and de-cohesion between fibers and matrix) as well as permanent deformation. The inter-laminar model is used to represent progressive delamination between the plies of the laminate. Numerical simulations are conducted with the SAMCEF (Siemens) finite element software. The parameters of the material models are identified based on specific physical testing at the coupon level. When applied to OHT, a so-called non local approach must be used to handle in a proper way the stress concentration that occurs at the border of the hole, and avoid localisation of damage issues. The characteristic length associated to the non local approach is an additional parameter that must be determined based on test results for specific OHT configurations, and then, once identified, used in the finite element models for the other studied OHT configurations. Comparisons between physical and virtual testing demonstrate the necessity to take the non local effect into account, and the capability of the simulation methodology to predict failure strengths of the considered OHT specimens. The approach is then validated on 4PB cases, with different stacking sequences and numer of plies; here again, simulation is compared to physical test results. [1] Hochard C., Aubourg P.A., Charles J.P. (2001). Modelling of the mechanical behavior of woven fabric CFRP laminates up to failure. Composite Science & Technology, 61, pp. 221-230. [2] Allix O., Ladevèze P. (1992). Inter-laminar interface modelling for the prediction of delamination. Composite Structures, 22, pp. 235-242. [3] Jetteur P., Bruyneel M., Craveur J.C. (2019). Structures en matériaux composites – calcul par éléments finis. Dunod. [4] Lahellec N., Bordreuil C., Hochard C. (2005). Etude de la rupture fragile d’un stratifié quasi-isotrope à plis tissés : mise en évidence d’une longueur interne. C.R. Mécanique, 333, pp. 293-298. [5] SAMCEF. Siemens PLM software.