Substantial growth potential for composite materials exists in the private sector, where high volume, low cost production is required. Post processing inspection can represent a significant percentage of the cost of composite products. Alternate ways of assuring quality must be examined. In-process inspection can be easily adapted to continuous composite manufacturing techniques such as the pultrusion process, enabling 100% inspection. Recent research efforts at the Center for Composite Materials has focused on ways of evaluating pultruded composites on-line by using ultrasonic non-destructive evaluation (NDE) techniques. The most accurate method to date is based upon Lamb wave velocity measurements. This inspection technique uses two transducers positioned at normal incidence to the composite in a through-transmission mode to generate and receive ultrasonic waves which propagate through the sample. Careful processing of the waveform data reveals the degree of porosity in the composite samples. A series of tests were performed in-situ on an actual laboratory scale pultrusion process which accurately predicted the porosity in a 6.4 mm multiplied by 3.2 mm (0.25' multiplied by 0.125') cross-section pultruded rod over a range of 0.5% to 12% void volume fraction.

Date Published: 7 July 1995
PDF: 11 pages
Proc. SPIE 2455, Nondestructive Evaluation of Aging Aircraft, Airports, Aerospace Hardware, and Materials, (7 July 1995); doi: 10.1117/12.213542

Published in SPIE Proceedings Vol. 2455:
Nondestructive Evaluation of Aging Aircraft, Airports, Aerospace Hardware, and Materials
Tobey M. Cordell; Raymond D. Rempt, Editor(s)