EDISON WELDING INSTITUTE COOPERATIVE RESEARCH PROGRAM (CRP)

Project Title: NDE of Composite Materials and Welds

Area: NDE

Project Number: J1175/B9010

Center: Edison Welding Institute

Contact: John C. Lippold

Phone: (614) 486-9400

Principal Investigator: Laszlo Adler

Institution: The Ohio State University - Welding Engineering

Initiation Date: 07/88

Completion Date: 06/91

Funding: N/A

Key Words: Composite Materials, NDE, Discontinuities

Abstract:

The use of composite materials in an increased number of engineering applications has resulted in more stringent demands for quantitative nondestructive evaluation (NDE) techniques. Detecting porosity, cracks, delamination and other discontinuities in composite materials is extremely difficult. Standard NDE techniques such as normal incidence pulse-echo are not practical in thin composite plates, which are both anisotropic and inhomogeneous. The back-reflected ultrasonic signal from the walls overshadow the ultrasonic scattered signal from a possible discontinuity. The inherent scattering from the fiber and then from the various plies produce additional signals. Lamb waves are much better suited for interrogating thin plates than bulk waves because the Lamb wave will propagate along the plate rather than through it. Two new immersion techniques are reported which use single transducer broadband leaky lamb wave modes. Results are presented from composite plates to demonstrate a four-to-five-fold increase in sensitivity for discontinuity detection compared to conventional C-scan techniques