| Description |
Lightweight composite materials are increasingly used as the material of choice in modern engineering applications. With the inevitability of damage that can occur to composite structures, it becomes necessary to design suitable repairs as well as predict the repaired performance. This research focused on scarf repairs, currently favored for use on composite structures. Composite scarf repairs were evaluated using a combined computational and experimental approach. A finite element-based methodology was used for predicting damage progressions, failure modes, and the resulting strengths of composite scarf repairs. Specialized mechanical testing was performed to calibrate damage parameters and cohesive interface elements. A parametric evaluation of representative composite scarf repairs was performed to investigate locations of damage formation, damage progressions, and predicted strengths. Experimental validation testing was performed on selected scarf configurations to determine damage progressions and ultimate strengths under tension loading. Representative composite scarf repair test specimens were designed and manufactured with scarf angles of 5˚, 10˚, and 15˚. Tension test results were compared to predictions from the finite element simulations to evaluate predictive capability. Results from finite element simulations, using calibrated cohesive elements along the scarf joint interface and progressive damage modeling within the composite laminate, were in good agreement with mechanical test results for the three scarf repair angles considered. Further enhancement of scarf repairs through the use of laminate pad-up scarf tip reinforcement was also investigated. As the scarf tip is a critical region of the scarf repair, it was hypothesized that adding reinforcement at the scarf tip would suppress damage development and significantly improve the strength of the scarf repair. Results from tension testing and finite element simulations showed the strength of the scarf repair with reinforcement to be nearly twice that of that of the unreinforced scarf repair. Additionally, analyses performed suggest that such reinforcement at the scarf tip may be capable of restoring the full strength of the structural component. iv |
