ND T abstracts

51293 Abbe, S.; Degait, A.; Honorat, P.; Renon, J.M. Industrial non destructive testing of composite materials by stimulated infrared thermography Non-Destructive Testing 92. Proceedings of the 13th World Conference on Non-Destructive Testing, Sao Paulo (Brazil), 18-23 Oct. 1992. Vol. 2, pp. 703-707. Edited by C. Hallai and P. Kulcsar. Elsevier (1992)

SEP (Societe Europeenne de Propulsion) has been using for more than 10 years, Stimulated Infrared Thermography for inspecting composite material parts or bonded structures. Specific methods have been perfectly in order to control new ceramical composite materials, developed by SEP. Results obtained on several hundred of parts which are currently industrially controlled will be presented. They show that SIT, performed on ceramical composite materials is a reliable, fast and repeatable technique.

51022 David, D.; Marin, J.Y.; Tretout, H. Automatic defects recognition in composite aerospace structures from experimental and theoretical analysis as part of an intelligent infrared thermographic inspection system Thermosense XIV. An International Conference on Thermal Sensing and Imaging-Diagnostics Applications, Orlando, Florida (United States), 22- 24 Apr. 1992, pp. 182-193. SPIE Vol. 1682 (1992)

The difficult identification of flaws on the infrared images due to the complex nature of the stimulated phenomena calls for efficient data processing in conjunction with thermal imaging, optimum heating and mathematical modelling of the heat diffusion. We have been carded out for the last two years a project integrating artificial intelligence which goal is to automatically recognize and size defects in order to output a diagnosis as a function of the design office acceptance criterias. This paper summarizes our approach and presents the theory behind it.

51020 Laine, A. Detection of failures in plastic composites using thermography Thermosense XIV. An International Conference on Thermal Sensing and Imaging Diagnostics Applications, Orlando, Florida (United States), 22- 24 Apr. 1992, pp. 207-212. SPIE Vol. 1682 (1992)

This paper presents results of detecting sub-surface defects from plastic composites using thermography. We have examined glass-fiber reinforced composites, which have several flaws occured during manufacturing. The results of thermography have been verified by using ulwa~nic or by cutting the specimen. Experimental results show, that flaws can be detected if the wall thickness of the object is small enough and delamination-like failure is bigger than wall thickness.

51018 Safai, M. Thermography evaluation of metal bonding materials Thermosense XIV. An International Conference on Thermal Sensing and Imaging Diagnostics Applications, Orlando, Florida (United States), 22- 24 Apr. 1992, pp. 234-238. SPIE Vol. 1682 (1992)

At Boeing Defense & Space Group Quality Assurance Research and Development, an investigation was conducted to determine the possibility of using thermographic technique to detect bonding anomalies in composite and aluminum structures. This paper describes the thermographic technique used for the nondestructive evaluation of bondline integrity in metal and silicone rubber bonded material.

51017 Maclachlan Spicer, J.W.; Kerns, W.D.; Aamodt, L.C.; Murphy, J.C. Source patterning in time-resolved infrared radiometry (TRIR) o f composite s tructures Thermosense XIV. An International Conference on Thermal Sensing and Imaging Diagnostics Applications, Orlando, Florida (United States), 22- 24 Apr. 1992, pp. 248-257. SPIE Vol. 1682 (1992)

A quantitative thermographic NDE technique for the characterization of composite materials is under development along with supporting theoretical analysis. The TRIP, technique differs from other pulsed thermography techniques in that the surface temperature of the specimen is monitored as a function of time during the application of a step heating pulse to the sample. Full-field images with temporal resolution faster than video frame rates are acquired with an infrared scanner by disabling the vertical galvanometer in the infrared camera and scanning the heating source across the sample. Alternatively, an lnSb focal plane array is used to acquire the time-resolved images. Experimental results in both simple and hybrid composite systems will be discussed. The depth and lateral extent of interlaminar separation in

composites will be presented and the use of lateral heat flow techniques to image vertical defect structures will be examined.

50524 Zhang, D.; Sandor, BJ. Advances in thermographic stress analysis and evaluation of damage in composites Composite Materials: Testing and Design, Vol. 10, pp. 428-443. ASTM STP 1120 (1992)

Development of the thermographic stress analysis CI'SA) method and the stress pattern analysis by thermal emission (SPATE) method for suess analysis and evaluation of damage in fiber-reinforced composites during the past five years is reviewed, and some new results are presented. The fundamental factors affecting the TSA signals, calibration methods, stress analysis, stress (strain) separation, and methods of qualitative and quantitative evaluation of damage are discussed. Reasonable future research topics are outlined.

50286 Corvasce, F.; Lipinsla', P.; BerveUler, M. Thermomechanical behaviour of metal matr ix composites Nondestructive Characterization of Materials, 3rd International Symposium, Saarbrucken (Germany), 3-6 Oct. 1988. pp. 194-203. Edited by P. Holler, V. Hauk, G. Dobmann, C.O. Ruud, and R.E. Green. Springer-Verlag (1989)

This paper deals with the modelling of the inelastic thermomechanical behavior of Metal Matrix Composites (MMC) within the framework of the classical uncoupled thermo-elasto-plasticity without damage. At first the local behavior of materials is presented, followed by the global or overall description. A general approach to the determination of concenwation tensors from the integral equation is proposed and next specialized for the case of the self-consistent scheme. A few applications are presented concerning elasticity (evaluation of the overall elasticity tensor), thermoelastieity (local stresses, thermal expansion coefficients,...) and elastoplasticity (stress-strain curves, residual s ~ . . . ) .

50280 Zenkert, D.; Vikstrom, M. Shear cracks in foam core sandwich panels: nondestructive testing and damage assessment Journal of Composites Technology & Research, Vol. 14, No. 2, pp. 95-103 (1992)

In the present paper, different types of shear cracks are simulated in foam core sandwich panels. They are inspected with a thermal nondestructive testing (NDT) method based on an infrared (IR) detector. It is found that all types of simulated cracks can be satisfactorily detected. An engineering approach is used to estimate the residual strength of the panels caused by the shear cracks. The panels are analyzed with the finite element (FE) method to compute fracture mechanics parameters. By using fundamental material data, such as the fracture toughness, the strengths of the panels in presence of the cracks are predicted. Finally, all panels are tested in four-point bending, and it is found that the experimentally measured and the predicted strengths agree well.

50014 Busse, G. Thermal waves for material inspection Physical Acoustics. Edited by O. Leroy and M.A. Breazeale. pp. 31-39. Plenum Press (1991)

Thermal waves, with their high attenuation, allow for remote near- surface probing of boundaries in materials at a range that can be tuned with the modulation frequency. Fibers and layers are features of interest for inspection. Therefore thermal waves fit well into the gap of existing conventional methods: ultrasonic methods are not applicable in the near-surface region and low reflection coefficient (like polyurethane coating on polyurethane substrate). Also, they require mechanical contact. On the other hand, X-rays allow for remote inspection but they are not sensitive to boundaries. There is no competition with optical methods which depend on transparency, since the thermal wave generation is based on optical absorption.

50012 Van Hemelrijck, D.; Schillemans, L.; Daerden, I.; De Roey, F.; Boulpaep, F. The use of thermoelastic emission techniques (Spate) for damage analysis of graphite epoxy composites Durability of Polymer Based Composite Systems for Structural Applications. Edited by A.H. Cardon and G. Verchery. pp. 325-335. Elsevier Applied Science (1991)

It is the intention of the authors theoretical and experimental results of the use of Spate on isotropic materials. Then, an attempt will be made to expand the theory to anisotropic materials. Tbe'busic thermoelastic formula will be updated and used in a program which predicts the spate output. Comparison of this output with experimental scans will be shown for

100 NDT&E International Volume 26 Number 2 1993