A CASE STUDY OF AN COMPOSITE AUTOMOTIVE ROOF

The automotive engineers are seeking the best manufacturing processes in order to meet the highly exigent requirements in terms of lightweight and cost. The main scope of the present paper is to give an understanding of the cost structures of Resin Transfer Molding (RTM), High Pressure RTM (HP-RTM) and Compression RTM (CRTM) manufacturing cells for production volumes of 90,000 automotive roofs per year. Filling and curing times, as well as pressure distribution, have been estimated by PAMRTM simulations. Equipment and tooling have been selected based on this information.

Finally, the roof costs for each RTM variant have been calculated taking into account the investments, energy consumption and plant costs. The main conclusion is that, taking conventional RTM as reference, cost is reduced by a 38% with HP-RTM technology, and by a 93% by CRTM.

The selected component for the case study is an urban car roof with a circular window

The cost of an automobile roof has been estimated for three RTM variants, conventional RTM, HP-RTM and CRTM. The main conclusion is that the cost for CRTM is the lowest one, whereas that for HP-RTM is 9.2 times higher and for RTM 14.8 times higher. The reason for such differences is the shorter injection time required for CRTM that allows setting a higher molding temperature and fastens the curing of the composite, resulting in a shorter cycle time for manufacturing a roof. The main
consequence is that, for manufacturing 90,000 roof/year, the CRTM cell should be equipped with a single press/mold, whereas 6 are necessary for HP-RTM technology, and 15 for conventional RTM. The plant area is also directly proportional to the number of presses, so costs are also higher for RTM and HP-RTM