Mesh-Independent Modeling and Moiré Interferometry Studies of Damage Accumulation in Open-Hole Composite Laminates

Abstract

A three-dimensional ply-level modeling of multiple matrix cracking near an open hole in a quasi-isotropic composite laminate was performed. A mesh-independent displacement discontinuity modeling method based on higher-order shape functions was constructed for this purpose. The mesh configuration is dictated by the boundaries of a specimen, such as the presence of a hole, whereas the matrix cracking surfaces are aligned with the fiber direction in a given ply. The surface of the displacement jump associated with matrix cracking was defined in terms of the domain Heaviside function approximated by using higher-order polynomial B-splines. Several matrix cracks in each ply of a [0/45/90/–45] s composite were modeled, and their effect on the fiber-direction stress magnitude in the 0° ply was examined. Up to 35% relaxation of the fiber-direction strain amplitude due to matrix cracking (splitting) in the 0° ply was predicted. The moir? interferometry was used to experimentally determine the strain and displacement fields in the surface layer of the same composite, previously prestressed beyond the damage initiation load. A good correlation between the experimental data and the stress redistribution predicted by the mesh-independent damage modeling technique was observed.