Adhesively-bonded repairs to fibre-composite materials I: Experimental

The performance of carbon fibre/epoxy repair joints, bonded using an epoxy film adhesive, under static and fatigue loading has been investigated. The repair joints were immersed in distilled water at 50 degrees C for periods of up to 16 months and the effect of the hot/wet environment on the static and fatigue strengths was evaluated. Residual strength tests, where repairs were subjected to fatigue followed by static loading, were also performed. The mechanical properties of the substrate and the adhesive forming the joint were determined. All tests were undertaken at room temperature. It was found that there was no major effect of the conditioning on the above properties and that the repair joints had a similar static strength to that of the parent material. In some cases, a video camera fitted with a macro-lens was used to record the repair during static loading; cracks of an average length of 2.6 mm were visible in the composite just before catastrophic failure took place. In contrast to the static properties, the fatigue behaviour of the repair joints was significantly inferior to that of the parent material. Finally, fatigue tests were also performed on relatively large repair carbon fibre/epoxy panels with centrally-placed repairs, The fatigue results obtained from the repair panels were in close agreement with the fatigue results obtained from the repair joints. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.