The Formulation of the Quadratic Failure Criterion for Transversely Isotropic Materials: Mathematical and Logical Considerations

The quadratic function of the original Tsai-Wu failure criterion for transversely isotropic materials is re-examined in this paper. According to analytic geometry, two of the troublesome coefficients associated with the interactive terms-one between in-plane direct stresses and one between transverse direct stresses-can be determined based on mathematical and logical considerations. The analysis of the nature of the quadratic failure function in the context of analytic geometry enhances the consistency of the failure criterion based on it. It also reveals useful physical relationships as intrinsic properties of the quadratic failure function. Two clear statements can be drawn as the outcomes of the present investigation. Firstly, to maintain its basic consistency, a failure criterion based on a single quadratic failure function can only accommodate five independent strength properties, viz. the tensile and compressive strengths in the directions along fibres and transverse to fibres, and the in-plane shear strength. Secondly, amongst the three transverse strengths-tensile, compressive and shear-only two are independent.

Automated summary

This paper re-examines the quadratic function of the original Tsai-Wu failure criterion for transversely isotropic materials and determines two troublesome coefficients using analytic geometry. The analysis of the quadratic failure function enhances the consistency of the failure criterion based on it and reveals useful physical relationships. The investigation shows that a failure criterion based on a single quadratic function can only accommodate five independent strength properties and only two out of the three transverse strengths are independent.