Mechanical Behavior of Active and Passive Strain Sections in CFRP Laminate under Uniaxial Tension

This study investigates the nonlinear behavior of quasi-isotropic CFRP laminate under uniaxial tension. To verify the convergence of the calculated and experimental deviations, the approximating nonlinear equations describing the upper and lower hysteresis loop branches were found. The formation of a hysteresis loop in the active and passive strain sections in CFRP laminate has been studied. The open hysteresis loop development stages are shown from maximum expansion to stabilization, and to the tendency of branches to connect and narrow the loop. The point of the maximum angle between the upper and lower branches of the loop is determined – the apex of the hysteresis loop at maximum deformation. The strain region is found, in which the branches of the loop are parallel. The equations are determined, describing the nonlinear behavior of modules of Ex(ε) in the sections of increasing and decreasing strain. The dependence between mechanical energy dissipation per unit volume and strain was obtained.