Balancing Processability and Mechanical Performance in an NGDE ‐Modified Epoxy Resin for Delaminated CFRP Laminates

ABSTRACT

Comparing precuring flowability and postcured mechanical performance is key in delaminated CFRP laminates. A neopentyl glycol diglycidyl ether‐modified DGEBA/MTHPA/EMI‐2,4 epoxy is designed for vacuum‐assisted delamination repair and the role of NGDE content in terms of resin viscosity, cured‐matrix and repair efficiency is assessed. Increasing NGDE contents continually decrease resin viscosity, leading to more reliable flowability as well as infiltration capability. Vacuum‐assisted resin injection was performed at room temperature, followed by curing at 60°C for 1 h, 90°C for 2 h, and 130°C for 3 h. Under these fixed processing conditions, the optimal repair performance was obtained at an NGDE content of 3 phr, with tensile‐ and flexural‐strength recovery ratios of 114.4% and 106.5%, respectively. This improvement was attributed to the balance between enhanced resin flow and infiltration into the delaminated interface and the preserved integrity of the cured epoxy network. Enhanced crack deflection and energy dissipation further improved interfacial load transfer and inhibited crack propagation. This paper provides a practical basis for designing epoxy repair formulations for delaminated CFRP composites.