SANDWICH BEAM COMPRESSIVE TEST METHOD.

Experimental data are presented which show that the sandwich beam in four-point bending could be used to obtain reliable compressive elastic constants for graphite/polyimide laminates although some difficulties were encountered measuring composite compressive strengths. Data were obtained for ultimate stress, ultimate strain, Young's modulus, and Poisson's ratio values in 117 K, room temperature, and 589 K test environments for the HTS1/PMR-15 material system. A total of 36 compressive tests on four types laminates were performed. Also, 24 tensile tests on the same laminate orientations were performed to obtain input to the analytical portion of this program. A portion of the beam test section was analyzed using a linear elastic finite element computer program to predict the stress state in the graphite/polyimide composite. Specifically, the influence of the honeycomb core on this stress state was analytically determined.