A non-local finite element model to assess the compressive strength of composite structures

Abstract

Compression failure is a mechanism of non-local ruin that depends on the composite structure (layer thickness, load gradient), which makes it a peculiarity. The mechanism has been described and modeled with particular numerical tools in the literature. Only a few researchers modeled the mechanism at a mesoscopic scale, which is limited to UD composites. A homogenized non-local finite element model is proposed in this article. This is similar to Mindlin's II gradient theory to assess the compressive strength of the carbon/epoxy long fiber composite at the mesoscopic/structural scale. The framework of this non-local modeling is more general than that of Drapier et al. (1999) to assess microbuckling phenomenon in UD and woven composites. The developed non-local numerical model has been implemented in User Element (UEL) subroutine for analysis in ABAQUS®, which permits the simulation of the behavior of 2D and 3D cases. A 2D continuous (C1) type super-parametric non-local element (NL U32) is developed for both linear and non-linear (geometry and material) case. Various tests results are presented to validate the non-local FE model for 2D case by comparing the results of the homogenized non-local element with ABAQUS® iso-parametric elements. The classical (elastic and plastic) and non-local material properties (elastic) of the non-local model are identified by comparison to the responses of a Representative Volume Element (RVE) of full heterogeneous microstructures. A comparison of the compressive behavior of UD composite with the results in the bibliography shows the capabilities of this numerical tool.