Measurements of the Out-of-Plane Displacement of an Axially Loaded Cracked Metal Sheet with a CFRP (Carbon Fiber Reinforced Plastics) Repair Patch

摘要

An adhesively bonded CFRP repair patch situated centrally on one face of a 1.6 mm thick sheet test piece of aluminum alloy 7475-T761 containing a central fatigue crack caused an out-of-plane displacement when the test piece was loaded in tension normal to the crack length. Out-of-plane displacements for crack lengths = 75 and 94 mm were measured. The magnitude of the displacement depends on crack length and is a nonlinear function of applied load. A greater displacement per load increment occurs at low loads and there is a tendency towards a limiting value at high loads. A moire shadow technique was used to measure displacements and the results agree well with dial gage measurements. Ultrasonic C-scan images reveal an adhesive debond region near the crack line at the center of a crack of length 94 mm. This debond is thought to be the reason for a disparity observed between displacement measurements on the patched and unpatched surfaces of the test piece.