X-Ray Measurement of Material Properties in Composites

Abstract

Advanced materials for use in the aerospace industry are presently being developed and applied at an astonishing rate. This pace is driven by the need for materials that can withstand higher operating temperatures and loads, yet remain cost competitive. As the performance demands of aerospace materials push nearer and nearer the theoretical limit for strength, the allowed flaw size in traditional materials is driven smaller, making quality control more stringent. This demand for improved performance characteristics is also generating strong interest in other materials such as: exotic alloys, ceramics and reinforced composites. A need exists for characterizing these advanced materials for composition variations, flaw content, inclusions and porosity using nondestructive techniques at all stages of the materials life cycle. These stages include initial characterization of a new material, process control during the manufacturing of the material, quality control of incoming material, and the in service inspection of the final part. The importance of quantitative measurement techniques is illustrated by porosity. The detection of porosity in ceramic composites is not sufficient, since good ceramic composites have a level of porosity easily detected. Knowledge of the amount of porosity is necessary to adequately characterize the quality of the material. The use of many techniques will be required for the adequate determination of the quality of these new materials. Ultrasonic, eddy current, thermal techniques, have been widely reported(l,2,3). One powerful technique for preforming these types of inspections that until recently(4,5) has been unsuccessful is the use of X-rays. Although the early results(6) using film based detection methods were unsuccessful due to insufficient sensitivity of the film, the use of scintillation detectors give excellent sensitivity and subsequently excellent results. In this paper we will illustrate the utility of an X-ray based technique for the quantitative determination of the levels of porosity in several classes of materials, metal matrix fiber, re-enforcement content, and the detection of process control problems in metal matrix composites, and the determination of the morphology of the flaw. Instrumentation