AID T abstracts

49017 Krynicki, J.W.; Nagle, D.C.; Green, R.E. Direct thermomechanical stress and failure mode analyses of a cloth reinforced ceramic matrix composite Nondestructive Characterization of Materials IV. Edited by C.O. Ruud, J.F. Bussiere and R.E. Green. pp. 329-336. Plenum Press (1991).

Since inherently brittle ceramics are often toughened through reinforcing fibers, the mechanical behavior of a ceramic matrix composite (CMC) is heavily influenced by the strength of its flberhnatrix interface, which is in turn directly related to the residual thermomechanical stresses present between the matrix and reinforcement. This study describes the use of photoelasticity to directly determine thermomechanical stresses in this engineering CMC. The use of acoustic emission (AE) and optical microscopy to characterize flexural test data in establishing fundamental failure mechanisms will also be discussed.

48768 Pearson, L.H. Diffuse reflectance IR spectroscopy for bonding surface contamination characterization Review of Progress in Quantitative Nondestructive Evaluation, La Julia, California (United States), 15-20 Jul. 1990. Vol. 10 A, pp. 581-588. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4.

Contamination in bondlines is a known cause for the existence of weak bonds or debonds in solid rocket motor (SRM) bondlines. Organic compounds exhibit IR spectral signatures that are characteristic of or unique to the particular material. Such spectral information can be used to identify the contaminant type since the spectral signature is largely preserved in the diffuse reflectance spectrum. This paper evaluates the application of diffuse reflectance spectroscopy on rough metal and phenolic composite material surfaces. The following sections discuss the experimental and analytical procedures developed for acquisition and interpretation of diffuse reflectance

48766 Sottos, N~.; Scott, W.R.; Ryan, M.I. Repeatability of local thermal displacement measurements near the fiber/matrix displacement measurements near the fiber/matrix interface using micro-interferometry Review of Progress in Quantitative Nondestructive Evaluation, La Julia, California (United States), 15-20 Jul. 1990. Vol. 10A, pp. 1057-1063. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4.

A scanning micro-interferometer is used to image thermal displacements of specimens consisting of a single, 30 m u m diameter carbon fiber embedded in an epoxy matrix. The interferometer design provides the necessary resolution to detect deformations on a scale commensurate with the dimensions of the fiber/matrix unit cell. This paper discusses the repeatability and accuracy of the thermal displacement measurements obtained with this method.

48765 Zalameda, J.N.; Winfree, W.P. The rma l imaging of graphite/epoxy composite samples wi th fabricated defects Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 15-20 Jul. 1990. Vol. 10A, pp. 1065-1072. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4.

The purpose of this work is to develop a thermal inspection system for quickly inspecting large area composites for increased reliability and maintainability of helicopters resulting from improved quality assurance manufacturing. In this research an infrared camera/image processor based inspection system is applied to image defects in composites. Noncontacting and single sided measurements were performed on graphite/epoxy samples with fiber volume fraction variations, fabricated porosity, impact damage and inclusions in uncured lay ups. These defects were imaged by determining the variations in the cooling rates caused by differences in through ply thermal diffusivity. The heating period data was not used due to heat source reflections which complicated data reduction. In addition the system's sensitivity to measuring the defects due to sample thickness is presented.

48764 Balageas, D.L.; Delpech, P.M.; Boscher, D.M.; Deom, A.A. New developments in stimulated infrared thermography applied to nondestructive evaluation of laminates Review of Progress in Quantitative Nondestructive Evaluation, La Julia, California (United States), 15-20 Jul. 1990. Vol. 10A, pp. 1073-1080. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991). ISBN 0-306-43903-4.

1 0 2 N D T & E I n t e r n a t i o n a l V o l u m e 2 6 N u m b e r 2 1 9 9 3

We have developed pulsed stimulated infrared thermography and have applied it to carbon/epoxy composites. Some progress has recently been made in the data reduction procedure, which is briefly discussed in the first section. Due to the relatively low refresh frequency of the cameras currently used, the application of the method has now been restricted to low thermal conductivity materials. We present here, in the second section, new developments of the data reduction procedure that allow this technique to be applied now even to good conductors, in particular to carbon/carbon composites.

48761 Dobie, D.; Celeste, J.; Krauter, G. Quantitative non-destructive environmental characterization of advanced mater ia ls Nondestructive Characterization for Advanced Technologies, Oakland, California (United States), 18-22 Mar. 1991. pp. 25-27. ASNT (1991).

Computer-controlled environmental chambers have been built to evaluate advanced materials such as polymethyipentene, polystyrene, agar, carbon and composites which have unique engineering properties. The test also assess the thermal and water absorption properties of these materials. New materials have demanded new engineering tests. This study has shown the need to develop new coefficients to describe the hygroscopic and thermal responses of these materials effectively, because each material responds differently. The importance of humidity control in the environmental characterization of advanced materials is now better understood, because of the tests described here.

48542 Burleigh, D. Thermal NDT application: inspection of a large graphite-epoxy tool NDT for Today's Applications, 1990 ASNT Fall Conference and Quality Testing Show, Seattle, Washington (United States), 18-12 Oct. 1990. pp. 96-98. ASNT (1990)

A large tool, made of graphite-epoxy and used for making parts of graphite-epoxy, was inspected using Thermal NDT. Although one severe defect in the tooting surface had been previously discovered by visual inspection, it was suspected that many more existed. A simple technique of Thermal NDT using hot air guns and a thermographie scanner was employed to inspect the tool. Many more defects were discovered. The inspection was fast, inexpensive, and effective. Subsequent attempts at one-sided ultrasonic inspection were unsuccessful due to the porous nature of the tool material. Through-scan ullrasonic inspection was not considered, because of cost and the fact that the part could not be exposed to large quantities of water.

48266 Ahmed, T.; Jin, H.I.; Wang, X.; Favro, L.D.; Kuo, P.K.; Thomas, R.L. Infrared thermal wave studies of composites Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, Califomia (United States), 15-20 Jul. 1990. Vol. 10B, pp. 2173-2179. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1991 ). ISBN 0-306-43903-4

Thermal wave techniques have received increasing attention for use in the inspection and characterization of composite materials. In this paper we demonstrate the ability of the technique to image flaws in several types of composite materials and to measure the depths of the flaws. Our infrared thermal wave imaging systems consists of an infrared camera and a real-time image processor under the control of a computer workstation. A bank of up to eight xenon flash lamps, each 6 kJ energy and 2 ms pulse duration, are synchronously pulsed to launch thermal waves into the target from its surface. Real-time image processing technique and averaging are used to enhance the subsurface selectivity of the defect detection.

47311 Britain, A.S.; Rapoport, D.A.; Budadin, O.N.; Simakina, N.I.; Abramova, E.V. Thermoholographic nondestructive inspection of articles made of polymeric composite materials Soviet Journal of Nondestructive Testing, Vol. 26, No. 11, pp. 822-829 (Jul. 1991)

A thermoholographic method and means of nondestructive inspection of articles made from polymeric composite materials (PCMs), which combine thermal and holographic methods for the purpose of uniting the functions of not only detecting flaws and determining their characteristics (e.g., geometric, thermophysical) but also analyzing the degree of their criticalness to correspondence to the fitness parameters of the inspected article, are proposed.