Elastic Response of Porous Matrix Plain Weave Fabric Composites: Part I—Modeling

In this first of a two-part series of papers, improved two-dimensional modified lamination theory and three dimensional finite element models are developed for the elastic analysis of plain weave fabric composites. New more accurate surface functions are proposed to model the geometry of the woven unit-cell. These geometry functions are implemented in both the analytical and finite element models which allows for direct model comparison. These models take into account the effects of the complex microstructure exhibited by both Chemical Vapor Infiltrated (CVI) woven ceramic matrix composites and traditional woven polymer matrix composites. The spatially dependent directional orthotropy of the fiber bundles is incorporated in both the analytical and numerical 3-D finite element models. In addition to the interbundle matrix porosity. the models also account for the presence of porosity within the bundles, as well as the presence of thin fiber and bundle coatings. The models are developed in a general manner such that they can be used to assess the effective elastic response of both stiff-ceramic and soft-polymer matrix woven composites. Case studies of pure remote tension and shear are formulated, and the theoretical platform required for the analytical and numerical evaluation of the in-plane effective elastic properties of stiff-ceramic and soft-polymer matrix woven composites is presented. Extensive parameter studies, discussion of the results and overall conclusions are reported in the accompanied manuscript with the title extension, Part II-Results. This work extends and refines previous micromechanical models aimed at predicting the macromechanical response of woven composite systems. It also establishes for the first time a hierarchical modeling framework, which is needed in the modeling of the effects of complex microstructures often exhibited by soft-polymer and stiff-ceramic porous matrix woven composites.