Out-of-autoclave scarf repair of interlayer toughened carbon fibre composites using double vacuum debulking of patch

Interlayer particle toughened carbon fibre composites play an integral role in the lightweight design of primary aerospace structures. We investigate an out-of-autoclave method using double vacuum debulking (DVD) to perform in-situ soft patch repairs. Utilizing the DVD process decreases the porosity of the co-cured film adhesive and patch from 4.7% to 0.4%, thereby increasing the flexural and interlaminar shear strength of 1D repair laminates by 30% to levels equal to autoclave cured laminates. In contrast, the higher void content did not significantly affect straight (2D) and round (3D) scarf repair strengths. 3D repairs showed significantly improved strength recovery compared to 2D repairs due to the stress shedding in the hoop direction. Finally, DVD process parameters may be optimized to reduce repair time by increasing the temperature and ramp rates while reducing the soak times, with no detrimental effects on porosity or strength observed.