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As the composites industry struggles to give a competitive edge to customers while continuing to be safe, efficient and good product stewards, the industry must continually reevaluate older processes with new materials. Years ago sheet molding compound (SMC) was the only way to achieve Class “A” surfaces. In the recent past, new low profile additive chemistry has allowed Class “A” surfaces to be made with the “old” resin transfer molding (RTM) process. Now, breakthrough resin technology allows Class “A” surfaces with even the older spray up process; and the industry is reinventing the SMC process with crystalline resin that can be compression molded into Class “A” surfaces at less than 200 psi. This paper will discuss current resin technology changes as well as the processes and tooling changes that have allowed these technology breakthroughs. Discussion will also center on the strengths and weaknesses of each material and process.

With the Elan's launch, Lotus is moving into a new era of low-volume production. By the middle of the next decade, a maximum of 3000 a year will be produced at Hethel and it was these requirements, combined with a desire for more design freedom, that led Lotus to carefully examine its current VARI (Vacuum Assisted Resin Injection) process and develop a unique, flexible system for the Elan. It was decided to develop a manufacturing process to employ a larger number of separate panels to allow future design freedom. The aim was to jig assemble panels which would allow accurate and consistent control of the complete assembly. Evaluation of alternative materials and processes for body panel manufacturing began in 1987, leading to the conclusion that the Lotus patented VARI process was still the most cost effective for the new car.

The production of FRP Class A surface parts for the automotive industry has been limited to high temperature SMC molding which requires chrome plated steel tooling and large hydraulic presses. The cost of this type of operation limits the economics of the process to a minimum of 30,000 parts/yr. Production runs of 3,000 to 20,000 parts/yr cannot justify hard tooling so other methods of production are used. These alternate methods have not offered the same quality of surface as the high temperature molding does. A new resin transfer molding resin. Arotran™ 50437, has been developed which can be used at mold temperatures as low as 120°F. Parts have been produced at tool temperatures between 120°F and 200°F with a surface comparable to that obtained with SMC. Molding produced at 120°F have utilized plastic tooling. Processing at 200°F, however, will undoubtedly require more durable tooling such as nickel shell molds.