Lamb wave reflection for the quick nondestructive evaluation of large composite laminates

The possibility of using Lamb waves for the long range nondestructive evaluation (NDE) of composite laminates has been investigated. Three different possible testing strategies using the S₀ Lamb mode - S₀ mode transmission, S₀ mode conversion to A₀ and S₀ mode reflection - are described and evaluated. It is shown that the S₀ mode reflection technique is the most promising method for long range inspection, 10-20 mm (0.4-0.8 in.) diameter delaminations being detectable at a range of a least 500 mm (20 in.). The time taken to test along a line using this technique is similar to that required to test at a point in conventional ultrasonic inspection, so considerable savings in testing time may be obtained.