Résumé:
Abstract
Composite materials satisfying certain demands of manufacturers on structure, physical and mechanical properties, etc. are widely used in aviation and sea ship building industry. Non-destructive inspection of composite materials differs from that of metallic materials for two reasons.
Firstly, physical properties such as thermal conductivity, acoustic attenuation, electrical resistivity and elastic behaviour are significantly different. This presents difficulties with the applicability of the physics of some of the techniques. Secondly, and more fundamentally, metallic structures are fabricated from feedstock, e.g. plate, bar and section, of known property, composition and quality. Subsequent inspection usually focuses towards joints, particularly welded connections
Composites on the other hand are heterogeneous and the material of construction and the component are formed in the one operation. Inspection therefore must be concerned with the whole surface of the structure a different scale of problem altogether. In addition the range of flaws which may need to be detected is much larger. As a result the NDT of composites is more complex than for metals both in terms of method of application and interpretation of results.
Microwave Nondestructive Testing techniques have advantages over other NDT methods (such as radiography, ultrasonics, and eddy current) regarding low cost, good penetration in nonmetallic materials, good resolution and contact less feature of the microwave sensor (antenna).
Microwave is an electromagnetic wave having a wavelength of 1 to 100 mm. By comparing with ultrasonics, microwave has an advantage that it can propagate well in the air. Therefore, a coupling medium is not necessary when the nondestructive inspection is carried out, and was the best solution in the case of composite. In these paper, we have developed a microwave simulation method for testing composite material, and their application for detecting surface cracks.
