Innovative inspection techniques
Demands on construction materials are ever increasing. The overriding goal is to create materials that are both stronger and lighter than traditional materials (e.g. steel). Metal matrix composites (MMCs) represent one class of these cutting edge materials. MMCs are composed of a metal matrix and a reinforcement or filler material. The reinforcement can either be continuous (monofilament or multifilament) or discontinuous (particulate, whisker, short fibre or other). Aluminum and its alloys are the primary metals used in MMCs. In comparison with traditional, non-reinforced metals, MMCs offer increased strength, stiffness, damping capabilities and resistance to wear and high temperatures. MMCs are also significantly lighter than their metal-only counterparts. High-profile research funded in part by the European Commission has led to the discovery of new MMC processes and materials. Of great importance is the optimisation of several non-destructive (ND) inspection techniques used to detect weaknesses in MMCs. Cone beam tomography is promising, but depends highly on proper instrument calibration and is not yet appropriate for single fibre applications. Ultrasonic detection of material flaws exploits differences in the acoustical impedance of the MMC. Small-scale defects are detectable when high frequencies are employed. Several other usable methods were also identified, such as SPICA-testing (thermal expansion) and 2-D X-rays (to recognise cracks). Apart from inspection methods, the work also sought to compare new MMCs with current industry (non-MMC) standards (e.g. titanium). A typical rib structure component was chosen as a test piece. The results show great potential, particularly for savings in production costs (31%) and component weight (26%). The research consortium is in the process of refining and disseminating the results of the project. The target sectors include defence, aerospace and the microchip industry. Armed with these new techniques and MMCs, Europe can assume a leading role in the advancement of materials science in the next several decades.
