A Study on Repair Means and Impact Load on Tensile Strength and Compressive Strength for Scarf Repair Part of CFRP Laminate Composite

When structures and products made with CFRP laminate composite plates get some local damage accidentally then need to be repaired, the scarf repair is done generally. In this study, the influence of the difference in the processes of scarf repair used in the structures of CFRP laminate composites on the tensile and compressive strength of the repaired parts were investigated and discussed. Two processes of scarf repair were used. One (ideal repair) was carried out under a sufficient condition having cleanroom and autoclave, etc. in a repair factory of aircraft maker and other (field repair) was done using some simple instruments in a laboratory expecting a field repair. Two ideal repair models (one of them was given an impact damage to its repair part) and one field repair model were prepared and each repair models were examined by tensile test and compressive test under the condition of room temperature in air, these strengths and fracture modes were discussed comparing among the three kinds of repair models. The following results are obtained. ⑴ The field repair model showed lower tensile strength by about 18 % compared with that of the ideal repair model. ⑵ For the ideal repair model with impact damage, in tensile test, its damage starting from local damage part by impact load generates the separation in adhesive layer. Thus, its tensile strength decreases by about 20 % compared with the ideal repair model without impact damage. ⑶ Both of two ideal repair models with/without impact damage and a field repair model showed almost same values in these buckling stress and compressive failure stress. ⑷ In case of that the compressive load acts in practical structure with scarf repair, the design of scarf repair should be considered with the influence of the load due to the out-of-plane deformation, which leads to separation in the adhesive layer.