Static strength of pultruded fiberglass composites at elevated and reduced temperatures under complex-stress state

Pultruded glass-fiber composites have been widely used in road infrastructure and in construction, but their strength characteristics under complex stress state at different temperatures have not been determined, which complicates their further implementation. This work is devoted to the determination of static strength and stiffness of pultruded glass-fiber composites under normal and shear stresses (induced by simultaneous axial loading and torsion of specimens) for three different temperatures. The paper reveals methodological aspects of testing under multiaxial loading, in particular, analyzes different variants of specimen tabs. The experimental part included uniaxial tensile, torsion, compression tests, as well as multiaxial combined tensile and compression tests with torsion at normal, elevated, and low temperatures. Sensitivity of pultruded glass-fiber composites to complex stress state is revealed. The failure envelopes were built for after axial and multiaxial testing at various temperatures. The failure criterion of the fourth order is proposed. The displacement and strain fields of the tubular specimens were analyzed using the VIC 3D at the chosen loadings and temperatures. The displacement fields were similar on the surfaces of the specimens that indicates of correct and uniform loading. The characteristic fractures were presented. The cracks on the specimens were different and correspond to respective loading parameters and temperatures. The obtained data allows to predict the failure of the pultruded glass-fiber composites under complex loadings and different temperatures, which is necessary for implementation of such materials.