Forming and structural integrity of lightweight materials for transport applications

Abstract

The research described in this PhD dissertation covers two aspects of lightweight materials for transport applications. One aspect is manufacturing process for lightweight metallic alloys and the other is structural integrity assessment for composite materials. In both cases, there was industrial interest in the research from aerospace, marine and automotive manufacturers. The first study relates to forming of lightweight metallic alloys. A new forming technique was developed to form lightweight turbine blade preforms. The second study relates to structural integrity of composite sandwich structures. The resistance of sandwich composite structures to high rate loading conditions from an air blast was investigated. In the first study, a novel electrical upsetting process, Gleeble Electrical Upsetting (GEU), was developed and conducted in a Gleeble 3800 Thermomechanical Simulator. By means of a resistance heating system in the Gleeble, a sharp decreasing temperature gradient and localized high upsetting ratio of an Aluminium Alloy (AA2011) round bar could be achieved. The forming results showed that three key forming parameters played important roles in the electrical upsetting process. The three parameters were heating rate, forming temperature and forming speed. A processing window was assessed to determine the optimum forming process for the GEU technique. In the second study, the air blast resistance of full scale GFRP and CFRP-skinned sandwich composite panels has been researched. Explosive charges of 38 - 100 kg TNT equivalent were employed in these studies to achieve high rate air blast loading. High-speed photography and DIC system were employed during the air-blast loading to monitor the deformation of these structures under shock loading. Failure mechanisms have been revealed using DIC and confirmed in post-test sectioning. Full-scale experimental results presented in this thesis were compared with FEA simulations. The two research studies performed in this PhD thesis emphasise the importance of manufacture process control and structural integrity assessment. In both cases, the materials studied are to be employed in transport applications. The Lee Family PhD Scholarship along with provision of testing materials from aerospace, marine and automotive manufacturers has provided for an interesting PhD study.