Residual deformations in obliquely reinforced fibrous composites: experiments on cyclic stretching

Abstract

Experimental studies of test samples from a obliquely reinforced composite based on carbon tape on cyclic stretching were carried out. It is established that the loading and unloading branches do not coincide, forming a hysteresis loop, and the axial deformation at each subsequent cycle at the same stress level in the cycle gains an increment that decreases in the initial cycles and tends to a constant value with a further increase in the number of cycles. This process is called the process of adaptability of the composite material. On the basis of tests on multi-cycle stretching of a composite with an aging after unloading, a viscoelastic component was distinguished from accumulated strain at each loading cycle. It is shown that at the initial cycles, the total strain accumulated in the sample by the end of the unloading process can be represented as a sum consisting of residual strain formed due to structural changes in the composite and creep deformation that disappears in the sample after unloading and holding during a long time.