Exceptions to the assumption underlying the so-called physically based failure theories

Li, Shugang and Sitnikova, E. (2019) Exceptions to the assumption underlying the so-called physically based failure theories. 22nd International Conference on Composite Materials, ICCM 2019, , Melbourne, Australia. 11 - 16 Aug 2019.

Record type: Conference or Workshop Item (Paper)

Abstract

This paper re-examines a well-accepted, mostly blindly, assumption adopted in many of modern composites failure criteria. After a brief review of its source, its inapplicability to heterogeneous and anisotropic composites has been argued rationally. As a further reinforcement to the argument made, two exceptions to the assumption have been cited first in the form of thought experiments and followed by physical experiments as the closest resemblances to the idealised thought experiments. In each case, fracture was observed in a plane on which macroscopic stresses vanish completely. The fracture observed cannot be attributed to the stresses exposed on the fracture plane. Any failure criterion based on this assumption is therefore not expected to predict the truthful material failure behaviour in a comprehensive manner. Any claim of the so-called 'physically based' criterion because it is based on this particular assumption is fundamentally flawed and therefore cannot be considered as credible. A new and rational approach will have to abandon this assumption before developing a reliable theory.

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