Bardet, Raphaël Régis
A life cycle assessment method for alternative material selection strategies in boat structures.
University of Southampton, Engineering and the Environment,
In general the use of composites results in shorter production time, lightweight and lower maintenance costs to the marine industry in the leisure, fast and fishing boats sectors. The social and economic benefits of using composite materials have made users complacent about the pollution and the health and safety issues associated with these materials. As the perception of environmental problems changes with time, alternatives with lower emissions allowing for cleaner production and easier disposal must be investigated. Glass Reinforced Thermoplastics (GRTP) have been in use for many years in the automotive industry and aerospace. These materials are fast to process, solvent free, have an unlimited pot life and demonstrate better mechanical properties such as improved toughness compared to aluminium and Glass Reinforced Thermoset (GRTS). However, building boats with GRTP requires massive investment in equipment that ship builders do not currently undertake, such as curing ovens, autoclaves and plastic welding equipment. It is, thus, necessary to define a method to measure the environmental performance of this material in the context of marine structure. The present research presents a comparative study of four materials, namely steel, aluminium, GRTS and GRTP, in the above context. The outcome of the research defines a material selection framework for marine structures focusing primarily on environmental performance. The study focused on life cycle energy and material flows to represent environmental impact over the entire life of a boat and the methodology used respects Life Cycle Assessment (LCA) standards. The influence of the conventional marine structure design approach on LCA results was highlighted by the result of a grillage and a boat design study. These two studies also showed that the contribution of in-service fuel consumption to the life cycle energy has the most significant environmental impact. This impact is two to three orders of magnitude larger than the manufacturing environmental impact of the candidate materials. A boat study taking into account the results of the two above mentioned studies overcame this limitation. This boat study, referred as a boat synthesis, uses a constant fuel consumption as a design constraint for each material. It demonstrated that in some part of the studied design space, GRTP could offer the best material alternative, whereas in some other part, aluminium is the best alternative. In addition, the study also showed that steel could also be the least environmentally damaging material under some conditions, which goes against the common practice to build all small boats in GRTS
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