Laminar Strength of GFRP under Combined Axial and Shear Loadings

Abstract

Insulation of superconducting magnets of fusion reactors and generators is subjected to simultaneous axial and shear stresses from cryogenic to elevated temperatures. GFRPs are suitable for these insulation systems. To investigate the laminar strength of GFRP, combined compressive and shear test with parallel-and series-type fixtures and off-axis tensile test were performed. The test results showed that each test gives a characteristic failure envelope. Taking account of the friction between specimens and fixture and stress distribution at the fracture origin, a unique normalized envelope is obtained. The envelope is divided in three domains ; (i) interlaminar shear fracture under tensile and shear loadings which obeys Mohr-Coulomb or Tsai-Hill model, (ii) interlaminar shear fracture with relatively low compressive stress whose shear stress increases linearly with increasing compressive stress, (iii) translaminar shear fracture with high compressive stress whose shear stress decreases linearly with increasing compressive stress.