Compression Creep of Pultruded E-Glass-Reinforced-Plastic Angles

Abstract

Results from an experimental investigation of the compression-creep behavior of thermoset-pultruded fiberglass-reinforced-plastic angle sections are presented. Tests were carried out on three 152 mm (6 in.) angle stubs made of isophtalic polyester resin with 53–59% E-glass fibers in weight. Each stub was instrumented with twelve 5-mm-long gauges in order to assess the variability of the strain measurements on the faces of the shape. Coupon-creep and stub tests were carried out simultaneously, and results of the two series of tests were compared to validate the use of coupon tests to predict creep deformations of full-sized members. The total duration of the tests was 2,500 h in creep and 250 h in creep recovery. Average predictions using Findley's power law with creep parameters determined from the stub tests and coupon tests agree with one another and with the actual creep strain measurements on the stubs. This indicates that there is no real benefit in making detailed creep-strain measurements on stub angles. The creepocity (ratio of creep strain to initial strain) measured on angle stubs is relatively small (14.4% after 2,500 h at a stress level averaging 45% of the proportionality limit) and should not cause geometrical integrity problems at the stress level considered. Finally, Boltzman's superposition principle was used to compare the experimental creep-recovery results with predictions from Findley's model, and agreement was also observed.