Optimize design of composite laminate scarf patch repair by numerical analysis and experiments

Abstract

Composite structures often experience various types of defects and damages during manufacturing, assembly, and service. In order to effectively restore the strength of damaged structures without compromising their original aerodynamic shape, adhesive repair is commonly employed. This paper investigates the tensile behavior of composite laminate. Initial tests include intact specimens, damaged specimens, and baseline scarf repair specimens. The load-carrying capacity and stiffness of the baseline repair specimens were both improved. Numerical analysis is developed based on the dimensions of the specimens. Numerical analysis model was established based on the dimensions of the specimens, employing continuum shell elements and cohesive elements to simulate the adhesive between the patch and the parent structure. The simulation results closely matched the experimental results, confirming the reliability of the simulation approach. Using this model as a basis, a parametric study is conducted on the patch repair parameters, including the scarf angle, the number of extra plies, and the overlapping width of extra plies. It is found that increasing the scarf angle and the overlap width of extra plies enhances the ultimate load capacity of the specimens, while increasing the number of extra plies improves the tensile stiffness. Subsequently, a scarf repair configuration with an angle of 1:50, an overlap width of 12.7 mm, and two extra plies is selected for the repair. Optimized scarf repair specimens are obtained and subjected to tensile testing. The results demonstrate that the optimized specimens exhibit excellent tensile performance, with an ultimate load reaching 93% of the intact specimens and a tensile stiffness in the linear range reaching 97% of the intact specimens.