Low-velocity impact damage tolerance of ultrahigh molecular weight polyethylene/carbon fiber laminates under prestress

This article provides a comprehensive understanding of the influence mechanism of prestress on the low-velocity impact behavior and damage tolerance of carbon fiber-reinforced polymer composite laminate toughened with ultrahigh molecular weight polyethylene fiber. Two kinds of prestress: uniaxial tension and uniaxial compression, were loaded by an innovative preloading apparatus, which has been patented with the number CN110426278A. Central composite design was adopted to design drop-weight impact test matrix considering both impact energy and preloading two factors. After the low-velocity impact test, residual bending stiffness and tension after impact (TAI) strength of the impacted laminates were tested. It was observed that the residual bending modulus and TAI strength of the impact specimens under preloading were higher than those without prestress. Through-the-thickness distribution of internal damage obtained by X-ray scanning and electron microscope analysis, together with fracture toughness analysis, were employed to explain the experimental findings and relevant mechanisms.