The prevalence of non-monolithic materials such as carbon fibre reinforced polymers (CFRP) in aerospace has introduced many new complexities to the materials industry. Sustainment and through life costs of military vehicles are often substantially greater than acquisition costs, and as such, efforts to improve reliability and minimise costs are significant. Regarding composite structures, scarf repairs are often used to restore strength to a damaged component, with a shifting focus to out-of-autoclave processes to reduce cost. The aim of this project was to identify the effects of processing techniques through the application of novel and standard assessment techniques.
Through the application of novel techniques, including pressure mapping and cure kinetics modelling, relationships surrounding bond quality and quality control were established. It was observed throughout this project that comparable strength and quality for DVB co-cured specimens with improved quality control was achieved when a caul plate was utilised. With consistent cohesive substrate failure (CSF) observed, 0.03 +/- 0.038 % average bond-line porosity, and an average tensile strength of 401 +/- 28 MPa, the quality and consistency of these specimens was significantly greater than other co-cured groups. It was also observed that the DVB cure cycle, when applied to the hard patch approach, resulted in decreased average tensile strength, indicative of an improper cure cycle. Cure kinetics modelling applied to the adhesive saw that the DVB process delayed the onset point by approximately 5oC and 30 minutes.
Additional work is required surrounding the cure kinetics for the prepreg system, in order to establish an optimized theoretical cure process. Additionally, further mechanical testing, porosity evaluation, and dielectric cure sensing will offer additional insights into the DVB co-curing process, allowing for standardized repair procedures to be developed
