Scarf Repair Joints in Carbon Fibre Reinforced Plastic Strips

Abstract

Various theoretical models are developed for scarf joint repairs in unidirectional carbon fibre reinforced plastic strips subjected to a tensile load. for the type of joint where the fibres of both the original and repair materials (the adherends) are aligned along the longitudinal axis of the joint (a dry/dry joint), a uniform shear stress is predicted in the adhesive layer. When the repair material is laid directly on to the scarf surface with the fibres inclined to the longitudinal axis (a wet/dry joint), it is shown that the degree of shear stress uniformity is a function of the scarf angle, but reaches a uniform state at slopes smaller than 1 : 30 when the joint stresses can be calculated very simply.

The theoretical work is supported by tests on a number of joints of both types. The test results show that the dry/dry joints are more efficient than the wet/dry joints, and that it is possible to achieve joint efficiencies at failure, under a static load, in the region of 90% with slopes less than or equal to about 1 : 65.