Lightening the load with composite materials

Cars are a conundrum – they have to haul a ton or two of metal just to move a single person from one place to another. Environmental awareness and increasingly strict laws are driving car manufacturers to produce vehicles that are more energy-efficient. This, in turn, means that cars need to lose weight.
A European research project involving many academic and industrial partners was launched this year. Members of the Hivocomp consortium, whose research will be carried out over a four-year period, will explore the potential of certain composite materials to be used on a large scale in the automotive industry.

“The problem with many of these materials is that they are not really compatible with mass production,” explains Véronique Michaud, professor in EPFL’s Laboratory of Composite and Polymer Technology. “In this program, we are evaluating two new families of materials: polyurethane-based composites (PU) reinforced with carr, and thermoplastics reinforced by polypropylene (PP), which also holds carbon.”

Each of these “families” has its advantages and disadvantages, which, for the moment, mean that they are not yet viable options for replacing steel in the structural parts of automobiles. “For assembly-line production, the processing time of these materials must be extremely short”, continues Michaud. “The fate of these elements at the end of their life cycle must also be considered; this is problematic for PU, which cannot be melted down.”

At EPFL, the researchers are working on characterizing the physical properties of these two kinds of composites, notably the internal constraints that appear when these pieces are manufactured, which can result for instance in deformations. The School, under the leading of Jan-Anders Manson, head of the Laboratory, is also in charge of preparing demonstration pieces for the entire project. The first structures will come out of their molds in 2013. For each of them, a complete energy budget must be calculated: lightening up a vehicle to reduce gas consumption is useless if more energy is needed or pollution produced from manufacturing the lighter materials! “You have to see how many kilometers it takes for the energy savings to kick in, and whether it’s worth it. For that, we have to take into account the entire life cycle of each component – the products used, the additives needed, the cost of recycling, and so on.”

All this information will be used to come up with a variety of “industrial scenarios.” At that point, it’s up to the car manufacturers, in full possession of the facts, to take the next step or not. But the fact that VW, Daimler and Fiat are participating in the consortium already indicates that the industry has its eye on these materials.