Earlier this year, BASF established a lightweight composites team to show its commitment to the growing importance of lightweight design in the automotive industry. The group focuses on the development of marketable materials and technologies that are suitable for manufacturing high-performance fiber-reinforced parts for automotive applications.
Via its broad product portfolio, BASF is able to investigate three different plastic matrix systems (polyurethane, epoxy and polyamide chemistries) simultaneously and intends to develop tailor-made formulations in close cooperation with customers. The company will be making a double-digit million Euro investment in development in this area in the coming years, according to Willy Hoven-Nievelstein, BASF’s head of the Engineering Plastics Europe business unit.
RTM and fiber-reinforced composites: easy-flowing and fast-curing. Resin Transfer Molding (RTM), can be used to produce large and complex composite components in a single press-form operation. This involves placing multilayer fiber structures in a heated mold that is mounted in a press. A liquid resin is then injected into the mold, wetting the fibers completely and then curing in a controlled manner. In the newly established RTM laboratory in Ludwigshafen and at polyurethane research in Lemförde, BASF engineers are working on the chemical and technical challenges posed by the new matrix solutions. The automobile components to be produced from these materials in the future will be able to withstand high loads despite their light weight.
In addition to the mechanical performance of the finished fiber-reinforced composite part, good flow characteristics and a short curing time of the resin components represent the primary challenges with all three material systems. BASF already offers solutions on the basis of epoxy and polyurethane systems under the brand names Baxxodur and Elastolit R, respectively. Epoxy resin systems from BASF are in use today for the rotor blades of wind turbines.
Both solutions employ novel curing mechanisms: thanks to their low initial viscosity, they impregnate the fiber structures very well and then cure within only a few minutes. Thus they address one of the problems that previously represented an obstacle to the use of high-performance composites in automobile production. They are self-releasing and can be processed on existing high- as well as low-pressure equipment. Moreover, the new polyamide systems that are currently under development can be welded easily and also recycled as thermoplastics. BASF is devoting significant effort on accelerated curing of the three plastic matrix systems, and thus a further shortening of the cycle time.
Carbon and glass fibers. Structural chassis or body components can be manufactured only from composite materials based on endless carbon or glass fibers, and require fiber contents of about 65 wt %. Endless fibers are already in use today in aircraft and wind power applications, in plant construction, in prototype construction and in short-run automotive applications. Carbon fibers impart very high stiffness as a reinforcing material and are thus of special interest. To interact with application engineers and end users at an early stage, BASF has recently become a member of Carbon Composites e.V. (CCeV), a competence network for carbon fibers and fiber-reinforced composite technology that was established in 2007 and now has more than 120 members. In addition to the performance of a reinforcing material, price and availability are important for rapid introduction of matrix systems to the market. Glass fibers show great potential here—the limits of their mechanical strength have not yet been reached, BASF says.
Multimaterial systems. The overall system consisting of plastic matrix and fiber reinforcement must be processable on a reliable basis and readily adoptable for high-volume production. Compared to conventional metal components, they will contribute to a weight reduction of about 50%. Established technologies that embed metal inserts or endless fiber-reinforced thermoplastic mats and UD tape (unidirectional fiber reinforcement) in plastic complement the new approach.
In addition, endless fiber-reinforced skin layers can be combined with lightweight foam cores to yield high-quality sandwich structures with exceptionally good specific part stiffness and good insulating characteristics in combination with low weight. The PU foam systems developed for such parts by BASF are characterized by high compressive strength and temperature resistance in conjunction with a low density.
Without such multimaterial systems, the next major advance in lightweight automotive applications will not be possible.—Volker Warzelhan, Head of Thermoplastics Research at BASF
At the same time, BASF is expanding the capabilities of ULTRASIM, its computer simulation tool, the objective being the ability to predict the behavior of complex endless fiber-reinforced composites as well.