Deformations of Reinforced with Unidirectional Carbon Fiber Yarns Polysulfone Under Long-Term and Cyclic Loads

The deformation features of a thermoplastic matrix under long-term and cyclic loads have not yet received the necessary broad coverage. The evolution of deformations and accumulation of tensile damage in polysulfone reinforced with unidirectional high-strength and high-modulus carbon fiber threads under long-term and cyclic loads are studied. Composites were prepared by im-pregnating carbon fibers with a polysulfone solution and then removing the solvent. Stress re-laxation, creep, and low-cycle fatigue, as well as the structure and nature of damage to materials under load, are studied. The dependence of the effective modulus of elasticity on the maximum applied stresses is studied. It is shown that in composite materials with a thermoplastic matrix, the tensile diagrams are nonlinear, and the effective modulus of elasticity increases with increasing stress. Poisson's ratio at the initial moment is close to those for the pure polymer and is about 0.40, whereas with increasing stress this value decreases to 0.19-0.22. Video processing of sample de-formation in combination with scanning electron microscopy allows us to evaluate local features of deformation processes in carbon fibers and identify the main patterns of damage accumulation processes under long-term and cyclic loads.