Fatigue Analysis of Pre-cracked Aluminium Alloy Thin Sheets Repaired with a CFRP Patch at Elevated Temperature
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The effect of fatigue life was studied at an elevated temperature of 80 °C of a centre pre-cracked specimen of aluminium alloy 6061-T6, repaired with a unidirectional carbon fibre-reinforced plastic (CFRP) patch. The patch was bonded only on one face of the aluminium alloy skin and tested under tension–tension fatigue load with a stress ratio of 0.1 and a frequency of 10 Hz. The performance of the two kinds of CFRP patches was studied with three-ply and five-ply patches. The fatigue life of pre-cracked bare specimen was improved substantially by bonding the CFRP patches. The performance of five-ply patch was significantly better than the three-ply patch. At low applied loads, the repaired specimen of both kinds failed with the growth of the crack tips all the way to the specimen edges. At high loads, the initial growth of fatigue crack was observed for few millimetres and the specimen failed due to the separation of the patch. At low loads and elevated temperature, the fatigue life was increased substantially over those of tests conducted at room temperature. However, at high loads, the failure life at elevated temperature was decreased significantly.
KeywordsFatigue analysis Stress ratio Frequency Constant amplitude loading Composite patch repair Crack propagation Final failure
This work is carried out with the help of research grant from ARDB (Aeronautical Research and Development Board), DRDO, New Delhi, for the project “Fatigue growth characterization at cold and elevated temperatures of thin aluminium alloy panel repaired with polymer composite patches”.
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