The Yeh-Stratton Criterion for Composite Materials

Abstract

A new criterion for composite failure is proposed based on the Yeh Stratton (Y-S) criterion which is proven to work well for isotropic materials. Since the Y-S criterion requires three yield strengths from simple tension, compression, and torsion tests, the Y-S criterion can be applicable for ductile materials as well as brittle materials with different strengths in tension and compression. Like many other theories of anisotropic materials which were developed from those of isotropic materials, the Y-S criterion is now generalized in this paper to examine the failure of composite materials. One unique feature of the Y-S criterion is in its ability to change its format depending upon what types of stresses are applied and what types of material strengths are considered. Thus, it is shown that the entire closed failure surface by the Y-S criterion is composed of piecewise surfaces. When a material is in compression as an example, the compressive strength should be the dominant critical strength, not the tensile strength. Accordingly, the failure function must be adjusted so that it can accommodate the compressive strength. It is shown that the failure surface of the generalized Y-S criterion will consist of piecewise surfaces depending on types of stresses and strengths of composite materials. The validity of the generalized Y-S criterion is examined with experimental results of off-axis uniaxial strength tests of unidirectional fiber composites, and cross-ply and angle-ply laminated composites. Comparisons were made with other well-known anistropic theories.