Influence of double vacuum debulking process on co-cured soft-patch carbon fibre composite repairs

Reliable composite repair processes are a necessity to support the operation of next generation lightweight commercial aircraft. In-situ soft patch repairs of aerospace structures made from carbon fibre reinforced polymers require curing of conventional autoclave prepreg materials in an out-of-autoclave environment, which can result in poor repair quality. We demonstrate that the use of a double vacuum debulking (DVD) pre-curing step for soft patch repairs can essentially achieve void-free repairs for prepreg materials with moderate to high solvent residue. Porosity reductions translated into an increase in flexural and interlaminar strength properties of 7.3% and 14.8%, respectively. The repair quality improvement due to void reduction in both soft patch and adhesive film resulted in a 19% increase in tensile repair strength. The work presented demonstrates the need to include a DVD pre-curing step to achieve the stringent manufacturers' repair porosity limits and performance requirements for highly loaded composite aircraft structures.