A testing program to determine the time-temperature response of unidirectional T300/934 graphite/epoxy materials is described. Short-term (15-min duration) creep test results of strip tension specimens with the load at various angles to the fiber direction and at various temperature levels are reported. It is shown that the material is elastic at all temperature levels when the fiber is in the load direction. On the other hand, when the load is transverse to the fibers the viscoelastic response is shown to vary from small amounts at room temperature to large amounts for temperatures in excess of the T_g (180°C). For other fiber angles, namely, 10, 30, and 60 deg, the response is similar to the latter.

The time-temperature superposition principle or the method of reduced variables is used to determine compliance master curves for each fiber angle tested. The 10-deg results are used to obtain the master curve for the in-plane viscoelastic shear modulus. A viscoelastic analogue to the elastic orthotropic transformation equation is used incrementally to predict the master curves for the tensile compliance of the off-axis specimen. The incremental procedure by which the predictions are made are described in detail. The predicted master curves are compared to the ones determined experimentally. Further, 25-h creep test results for T = 180°C are compared to predictions. Agreement between theory and experiment in all cases is reasonable.