Sheet moulding compound (SMC) composites are a cost-effective alternative to metals for applications within the transportation industry. SMCs are lightweight materials with excellent properties, including high-corrosion resistance, and they are suitable for medium to high-rate processing. SURFAS is helping to increase the use of SMCs in the automotive industry, improving the appearance and performance of a variety of road vehicles.
"These composites are starting to be used more widely as a replacement for steel in automotive body panel applications," says Véronique Michaud of the Laboratory of Polymer and Composite Technology in Lausanne. "They suffer, however, from major drawbacks in terms of reliability, and surface appearance. Simply stated, it is extremely difficult to obtain, in a reliable manner, a surface quality that matches that of steel, especially after the painting operation."
The goal of the project was to investigate problems of surface quality in SMC composites. One issue identified by SURFAS partners at the beginning of the project was the presence of surface craters or pits on composite parts.
"EUREKA gave us the opportunity to cooperate on a European level, without the heavy administrative constraints of a typical European project."
Laboratory of Polymer and Composite Technology, Ecole Polytechnique Fédérale de Lausanne, Switzerland
"At that point, nobody knew why these craters appeared," explains Michaud, "so a main goal was to understand what was happening, at all stages of the process, from fibre production and the deposition of the sizing layer to compounding the composite pre-product, up to the final processing of the part. From there we hoped to make proposals on how to modify either the base material or the process to better control surface quality."
The project delivered an array of important scientific results, says Michaud. First, partners gained a better understanding of the role of fibre sizing and over-sizing on the final part quality and how parameters such as fibre surface energy, permeability and rigidity affect final product quality. They also investigated the exact mechanisms of the so-called ‘low profile effect’, where a blend of thermoplastic and thermoset resin is used to improve the final surface quality.
"We also developed several testing protocols that were implemented by our industrial partners," says Michaud. "New formulations were proposed, which were tested not only in the laboratory, but also in real-part production at a moulder's site." Finally, SURFAS partners investigated SMC recycling, of crucial interest for their use as a metal replacement.
In the European automotive sector, SMCs represent 90,000 tons of material per year and are currently used mainly for structured parts such as bumper beams, front-end panels or oil sumps. Aesthetic SMC parts, which represent about 29,000 tons of material per year, are mainly used in truck cabin components such as steps, spoilers and front panels, and in public transport vehicles, such as trains and buses. The car body application currently represents only a small part of the total SMC market.
"SMC moulders want to meet new productivity and surface quality demands," says Michaud, "and in this way considerably raise their market share in body panel applications." Most European experts do believe this objective can be reached, considering the increasing use of SMC body panels in the American market.
For car manufacturers, the results of SURFAS mean a better understanding of the complete SMC composite production process, potentially reducing development time and resulting in fewer initial production problems and corrections.
"The direct outcome for our company is two-fold. First, we are now better armed to develop new products in this or similar domains of application, thanks to all the technical knowledge that we gained. Second, we have increased our credibility and image with respect to our customers."
Vetrotex International, France
"EUREKA gave us the opportunity to cooperate on a European level," says Michaud, "without the heavy administrative constraints of a typical European project. All partners could deal with their local funding agencies, with whom they were already familiar and who reacted quickly and remained closely involved in project progress."
Dr. Michel Arpin works for SURFAS industrial partner Vetrotex International. He says the project was an excellent opportunity to investigate a technical issue from a more scientific perspective.
"The direct outcome for our company is two-fold," he says. "First, we are now better armed to develop new products in this or similar domains of application, thanks to all the technical knowledge that we gained. Second, we have increased our credibility and image with respect to our customers. Finally, this project has helped us to point out clearly how complex the materials-process-performance interaction is with this type of composite material."
"We hope this project has contributed to the increased use of SMC in the automotive industry," says Michaud. "These materials are lighter than metals and more resistant to corrosion. They will not only help us make nicer cars, but also, most importantly, lighter cars. This is a crucial step in reducing fuel consumption and the emission of carbon dioxide and other greenhouse gases. Together with improved engine systems, these materials can contribute to meeting EU regulations concerning emissions, and to reducing the impact of modern transport on the environment."