WEIGHT FUNCTION BASED MICROSCOPIC ELEMENTS FOR MULTISCALE A-FEM ANALYSES OF COMPOSITES WITHOUT HIERARCHICAL HOMOGENIZATION

摘要

The progressive failure process in composites involves many types of damage initiating andpropagating in a strongly coupled fashion. The various damage modes typically include plycracking, delamination, fiber rupture (in tension), and kink band formation (in compression), etc.Recent developments in advanced numerical methods such as X-FEM and A-FEM have beenable to treat such coupled damage evolutions, provided appropriate crack initiation andpropagation criteria are available. Currently strength criteria calibrated from individual damagemodes are being used. However, recent multiscale composite simulations and high-resolutionmaterial characterizations have shown that the crack initiation is significantly influenced by localmaterial heterogeneity at single fiber scale (～ 5- 10 microns). The empirical based initiationcriteria cannot reflect such reality and needs further improvement. In this paper, we shall seek amethod that has the potential to yield high fidelity damage initiation prediction with explicitconsideration of local material heterogeneity. The approach employs weight-function method toanalyze the microscopic failure with a domain that contains large enough number of randomlydistributed fibers. Concentrated local stresses due to local material heterogeneity and crackingare computed through a generic 3-fiber interaction problem with varying local materialheterogeneity. The results will then be applied to the entire domain using weight functionmethod. The method needs not to solve the inverse problem with large degree of freedoms.Therefore the microscopic analysis will be very fast and efficient.