Sensitivity of orthotropic material parameters used within the strain invariant failure theory

Understanding failure within composite materials has been an ongoing area of research over the last several decades. The difficulty in understanding their properties is fundamentally due to the nonhomogeneous nature of the microstructure, which is made up of two materials with distinctly different properties. Many newly emerging failure theories to acknowledge this non-homogeneity using Representative Volume Elements (RVEs), where the properties of the fibre and matrix constituents are retained throughout the modelling process. However, this improvement made in the analysis procedure is complicated by the requirement to obtain a full set of orthotropic material properties. The fibre and matrix constituents are often assumed to be isotropic on their own, but this is not the case. In this paper the authors examine a physics based failure criterion; the Strain Invariant Failure Theory (SIFT) and its sensitivity to various anisotropic material properties. It was found that assuming the fibre to be isotropic was responsible for 55% difference in the failure criterions’ prediction. Given this significant difference, additional examination of constituent properties and their effects on these dehegemonised failure theories was looked at.