Composite Scarf Repair with Different Materials in Airframe Structures

摘要

Parametric analysis via finite element (FE) method was adopted to study the composite scarf repair with different materials in airframe structures. The analysis of modulus variations shows that the longitudinal and transverse moduli of unidirectional ply have different influence on scarf repair. The study also indicates that mixed variation of longitudinal and transverse moduli will further the influence on strain levels. Research shows that a lay-up of [45/-45]_(4s) is too soft for the given structure and results in lower strain level in the parent structure near bondline along the load direction. [0/90]_(4s) lay | | up shows desirable stiffness but usually causes strain concentration at parent structure near bondline. Further study indicates that the equivalent modulus difference between the repair patch and the parent structure is an essential criterion for repair design. Severe thermal stress analysis indicates that thermal loading affects the stresses in bondline slightly for repair patch which is quasi-isotropic or has identical in-plane stiffness at the two directions.