MICROMECHANICAL CHARACTERIZATION OF CYCLIC PLASTICITY OF IM7 5260 COMPOSITE AT VARIOUS TEMPERATURES/

Uniaxial cyclic tests were performed on composite IM7/5260 and matrix Narmco 5260 specimens at 24 degrees C (75 degrees F), 107 degrees C (2 25 degrees F) and 149 degrees C (300 degrees F). Based on the test res ults, a constitutive model was obtained to describe matrix cyclic plas ticity. Subsequently, by assuming linear elastic behavior for fiber IM 7 and perfect bonding between fiber and matrix, a simple micromechanic al model was used to predict the cyclic behavior of the composite. For initial loading, model predictions agree with experimental results ve ry well. For the subsequent cyclic loading, the model underestimates t he average stiffness over a cycle, and the matrix properties require a djustments to yield satisfactory results.