Failure behavior of on-site repaired CFRP laminates

Abstract

On-site repairs of carbon fiber reinforced polymer (CFRP) composites involve out-of-autoclave curing, which increases the defect density and reduces the mechanical properties. This work aims to understand the strength and the associated failure mechanisms of on-site repaired woven CFRP laminates through experiments and simulations. A series of wet lay-up and prepreg step repaired specimens produced according to standardized aerospace procedures were tested under uniaxial tension. Wet lay-up repair provided a strength recovery of 66%, whereas prepreg repairs maintained 76% of the original strength. Finite element modeling closely predicted the experimentally observed behavior and showed that stress concentrations due to the adhesive-adherent stiffness mismatch are the primary causes of the lowered strength. The findings provide systematic experimental data and an accurate modeling framework to design and implement effective repairs in practice.