A Strength Prediction Methodology in Regions of Matrix-Dominated Stress Concentrations

Abstract

A point stress criterion based on stress distribution, in conjunction with Hashin's interactive failure criteria for fiber composites, is applied to composite laminates containing throughthickness discontinuities. The point stress criterion assumes that failure occurs when the stress over some distance (characteristic distance) from the discontinuity is equal to or greater than the strength of the material without the discontinuity. The characteristic distance is determined from Vnotched beam specimens cut through the thickness of AS4/3501-6, S2 glass/3501-6, and AS4/PEEK unidirectional laminates. This characteristic distance is then used to estimate the strength of inplane Vnotched beam specimens, transverse flexure specimens, and an AS4/PEEK doublenotched cylinder loaded in axial compression. Good correlation between the predicted and measured strength was obtained for this case. Based on these results, additional investigations with other material systems and more interactive stress states are warranted.