Time Dependent Behavior of Laminated Composites at Elevated Temperatures

Abstract

Models are presented for describing the time dependent viscoelastic and viscoplastic stress-strain relationships of unidirectional fiber reinforced thermoset matrix composites exposed to elevated temperatures. For Fiberite T300/976 graphite-epoxy com posite the constants in the stress-strain relationships were determined from data obtained in four point bend tests over the range 75 to 350°F. A procedure is also described which, together with the stress-strain models developed in this study, can be used to calculate the stresses and strains in loaded multidirectional laminates at high temperatures. Strains in loaded multidirectional Fiberite T300/976 laminates were measured as a function of time at temperatures varying from 75 to 350°F. Strains calculated by the models were compared to these data, and good agreements were found between the analytical and experimental results.