Prediction of statistical life time for unidirectional CFRTP under creep loading

Abstract

Recently, a thermoplastic epoxy resin (TP-EP) was developed at the Innovative Composite Center of Kanazawa Institute of Technology. Resin-impregnated carbon fiber reinforced TP-EP (CF/TP) strands molded by pultrusion were developed for use as tension rods by Komatsu Matere Co. Ltd. This study examines the prediction of the statistical life time for these developed CF/TP strands under creep tension loading with comparison to similar prediction for CF/TS strands having a thermoset epoxy resin (TS-EP) as matrix described in our earlier report. First, a test method for creep strength and static strength at elevated temperatures was developed for CF/TP strands. Second, the static tensile strengths of CF/TP strands were measured statistically at various constant temperatures under a constant strain rate. The statistical creep failure times under tension loading for CF/TP strands were predicted at a constant temperature by substituting the statistical static strengths into the formulation based on the matrix resin viscoelasticity. Third, the validity of predicted results was clarified by comparison with the creep failure times measured statistically using creep tests for CF/TP strands. Finally, the relation between the failure probability and creep failure times for CF/TP strands at various loads and temperature conditions was discussed by comparing the result of CF/TS strands with those for thermosetting epoxy resin as the matrix.