Thermoviscoelastic Characterization and Prediction of Kevlar/Epoxy Composite Laminates Available to Purchase

Unidirectional fiber-reinforced plastic (FRP) composite lamina, made from Kevlar 49 fibers and Fiberite 7714A epoxy, were characterized for nonlinear thermoviscoelastic response using the time-temperature superposition principle (TTSP). Mechanical static creep and creep recovery tests were performed using strain gages on 0°, 10°, and 90° unidirectional specimens at numerous temperature and stress levels. Master curves and shift factor functions for all four orthotropic material properties (fiber direction S₁₁, fiber/transverse coupling direction S₁₂, transverse direction S₂₂, and shear S₆₆ compliances) were obtained. Results were used in a numerical procedure to predict the viscoelastic response of general laminates. Predictions are compared with actual test results on selected two, three, and four fiber direction laminates made from Kevlar/epoxy.