Towards optimization of composite repair patch manufacturing for automated fiber placement

Repair involving composite patches are widely used in the aerospace industry as they allow for extended service life for aging aircraft structures and reduced turnaround time for aircraft to get back in the air. However, repairs in the field are currently performed manually; extensive training is required to acquire the skills needed for surface preparation and adequate repair patch application. The focus of this study is to investigate the manufacturability of adhesively bonded composite scarf repair patches using automated fibre placement (AFP). A simulation of the automated process for repair patch manufacturing was performed and a finite element model was built to examine stresses in the repair patch and the adhesive layer when subject to in-plane tensile loading. Two distinct repair patch shapes were investigated. The first model consisted of a circular repair patch replicating typical manual scarf repair with circular layers. The second model represented an AFP produced repair patch consisting of several layers of discrete composite tows with straight-edge endings. The resulting mechanical behavior for both repair patch shapes was assessed and compared by analyzing stress peaks and stress distribution in the composite repair patch layers and in the adhesive layer. The results and analysis presented may provide a guide to repair and research engineers wishing to use AFP technology for composite repair patch manufacturing.