An inelastic finite element model of 4D carbon-carbon composite

Abstract

Sepcarb 4D is a carbon-carbon composite material wherein the reinforcing fibers are bundled in four directions. It is widely and successfully used in integral solid rocket nozzles. However, an accurate prediction of the material behavior is difficult, due to the anisotropy and above all to the nonlinear inelasticity of the composite. An elastoplastic finite element model, including homogenized monoaxial stiffnesses, is presented. A consistent set of constitutive constants is obtained from test data. The adequacy of the model is demonstrated through comparisons between predicted and measured test results of Sepcarb 4D uniaxial specimens and rings. Results showing the significant influence of the orientation of the 4D reinforcement s relative to the applied load are discussed. The model can be extended to an increased number of directional composites and offers new possibilities in the stress analysis of such materials.