Mechanical properties of the repaired composite materials

Composite materials are widely used in the aviation industry due to their excellent mechanical and thermal properties. During manufacturing and in-service stage some defects may occur on the composite structures. Especially, external impacts can cause combined damages to the structures. Since composite structures are more sensitive to those damages, it has led to the search for reliable composite repair methods. Generally, due to economic reasons, repairing is preferred provided that design requirements, instead of to change with a new one.Beside the current repair techniques, new techniques have been in the investigation stage. The main currently used techniques include adhesive external patch bonding and scarf-stepped type repairs. Scarf-stepped repair method is the most preferred for their stiffness and longevity features. In this thesis, the stiffness and tensile strength of different scarf-stepped repair design types were investigated experimentally considering various step sizes. Produced Glass/Epoxy test specimens were damaged performing Quasi-static indentation (QSI) and tensile tests. Damaged and original plates were compared for damage resistance considering directly damage results before and after repair processes. The results indicated that stiffness of the repaired specimens was significantly affected by step sizes.