A Multiscale Framework for Predicting the Performance of Fiber/Matrix Composites

Abstract

To enable higher fidelity studies of laminated and 3D textile composites, a scalable finite element framework was developed for predicting the performance of fiber/matrix composites across scales. Effective design paradigms and lessons learned are presented. Using the developed framework, new insights into the behavior of laminated and woven composites were discovered. For a [0/90]s and [±45/0/90]s laminated composite, the classical free-edge problem was revisited with the heterogeneous microstructure directly modeled, which showed that the local heterogeneity greatly affects the predicted stresses along the ply interface. Accounting for the microscale heterogeneity removed the singularity at the ply interface and dramatically reduced the predicted interlaminar stresses near a free-edge. However, the heterogeneous microstructure was also shown to induce a complex stress distribution away from the free-edge due to the interaction of fibers near the ply interface, since close fibers were shown to induce compressive stress concentrations. The fiber arrangement had a significant effect on the local stresses, with a more uniform fiber arrangement resulting in lower peak stresses. Finally, the region needed to accurately predict the microscale stresses near the ply interface was shown to be much smaller then entire ply. For two types of orthogonally woven textile composites, nonidealized textile models were created and subjected to a variety of loads, providing insight into how load is distributed throughout the complex tow architecture and the locations of critical stresses. By comparing the stresses of a textile model with and without binders, the binders were shown to greatly affect the distributions of stress a tensile load but not in-plane shear. Variations in the local fiber volume fraction within the tows were shown to significantly affect the magnitude of critical stress concentrations but did not change where the critical stresses occurred. Finally, accounting for plasticity in the neat matrix pocket of the textile was shown to only affect the localized region near where binders traverse the thickness of the textile.