Experimental and micromechanical investigation of T300/7901 unidirectional composite strength

Abstract

We experimentally find mechanical properties in uniaxial tension/compression and torsional deformations of the 7901 epoxy resin used as a matrix to fabricate T300/7901 unidirectional (UD) fiber-reinforced composite. A series of off-axis tensile tests on the composite were conducted, and micrographs of the fiber–matrix interface at different load levels, using a Scanning Electron Microscope, taken to ascertain their ultimate tensile strengths. Values of the elasto-plastic parameters for the epoxy determined from the tests, and the handbook values of the fiber parameters were used in a micromechanicsbased bridging model to predict ultimate tensile strengths of off-axis loaded composite by considering stress concentration effects due to debonding at the fiber/matrix interface. For the 30 off-axis loaded laminate, the predicted ultimate strength is found to agree well with that determined experimentally, and the interface debonding occurs before the ultimate failure. The UD composite is assumed to fail when either the fiber or the matrix failure criterion is satisfied. POLYM. COMPOS., 40:2639–2652, 2019. © 2018 Society of Plastics Engineers