Study on impact performances of scarf-repaired carbon fiber reinforced polymer laminates

Composite structures used in aircraft are vulnerable to low-velocity impact and replacing them with new ones requires significant cost. Scarf-repair technique is an effective method to restore the stiffness and strength of damaged composite structures. Previous studies on scarf-repaired composite laminates have focused on stiffness and strength recovery efficiency, but limited attention has been directed toward the impact properties. However, scarf-repaired composite laminates are also sensitive to low-velocity impact. The residual strength is worth investigating to ensure the safety of scarf-repaired composite structures. In this study, experiments were conducted to test the residual compression strength after impact. Two main factors, namely impact energy and location, were considered. Finite element models were established to analyze the influences of these two factors and to predict the residual strength. Impact damages were introduced by degrading the mechanical properties in the damaged area estimated through the C-scan photographs. Results indicated that the damage area was larger when the impact was applied at the bondline of the top surface and the residual strength was the smallest. Increasing the impact energy caused large damage area, in which the residual strength declined. The predicted residual strength agreed with the experimental results well.