Lightweighting was the theme throughout the SPE’s 15th Automotive Composites Conference & Exhibition (ACCE). And with good reason: In 2011, the Obama administration announced new vehicle fuel-efficiency standards that require cars and light-duty trucks to average 54.5 mpg by 2025. Since then, every automotive manufacturer has raced to pursue lightweighting strategies.
Just before the conference, long-fiber thermoplastic (LFT) provider PlastiComp, Winona, Minn., announced the commercializion of its Complet Hybrid long glass+carbon fiber composites in two additional thermoplastic polymer matrices. These “hybrid” products, which combine long glass and carbon fibers in a single pellet, are now available in PP and engineered thermoplastic polyurethane (ETPU); last year they were initially introduced in nylon 66.
During ACCE, Eric Wollan, PlastiComp technical director, said hybrid LFT composites provide a “stepped approach to decreasing mass and cost while providing opportunities to optimize performance with different fiber mix ratios.” Initial trials have indicated that long glass+carbon fiber hybrids could bridge the performance gap between either fiber type alone. Wollan further noted that hybrids could lower the cost barrier to utilizing carbon fiber’s performance benefits. He emphasized that it’s not simply a question of substituting one material for another; rather, integration of design, material, and process is required to maximize the benefit of material change.
“The automotive sector has been adopting long-glass PP for a couple of decades because it offers significant weight reduction compared with traditional metal components,” Wollan said. “To meet increasing fuel-economy regulations, they still need to go lighter, but LFT-PP can’t get any stronger, and jumping straight to carbon fiber is a bold economic step for a price-sensitive industry. Using our long glass+carbon hybrids, we can incorporate carbon fiber in small increments to achieve the performance boost needed to switch more components from metal to plastic while keeping material costs reasonable.”
News in thermoplastic composites was also presented by BASF Dispersions & Pigments Div. (U.S. office in Florham Park, N.J.;). Henning Karbstein, manager for new business development and idea management at BASF, discussed the company’s thermoplastic versions of its Acrodur acrylic binder system. These one-part binders are supplied as aqueous solutions and latex dispersions that are free of solvents, formaldehyde, phenol, isocyanate, or other VOCs. They have low viscosity for impregnating fibers, allowing production of prepregs at room temperature. They exhibit thermoplastic behavior before cure; these semi-finished goods are thermally formable and cure at elevated temperature into thermoset composites with water the only byproduct of cure.
Called Acrodur Power 2750 X, the newest product in the line is designed for production of natural-fiber composites for lightweight automotive applications such as interior door panels or shelves. Unlike thermoplastic binders based on PP, it allows the use of up to 75% natural fibers in lightweight components, according to BASF. Karbstein said that the new thermoplastic grades allow cost-effective cold-press processing and short cycle times, while also achieving significant weight reduction (20% or more) vs. PP. The combination of compression and back-injection molding has further potential for design and strength/weight performance. Natural fibers bonded with Acrodur Power 2750 X can be processed using standard thermoplastic cold-forming methods and can be combined in a single process step with complex plastic elements such as reinforcing ribs or supports.
ADDITIVE MANUFACTURING GROWS
Perhaps a sign of its progress in the automotive market, this was the first year for the ACCE to feature a track dedicated to additive manufacturing/3D printing.
James Orrock, v.p. of FDM materials development for Stratasys, Minneapolis, showcased several examples of the company’s automotive rapid-prototyping capabilities. The company has worked with several OEMS on using additive manufacturing to create realistic headlamp prototypes, strong test fenders, and lightweight, ergonomic factory fixtures.
One example cited was a bumper fascia used to confirm exhaust-gas flow testing and layout. It was built from PC in five sections and then solvent bonded. The model took about 4.5 days’ run time in two Fortus 900mc FDM machines to print it, and the material cost was $3000.
Stratasys also spoke of the “next generation” of 3D-printing composites. Combining carbon fiber and PEKK offers impressive physical properties in additive manufacturing, Orrock said. Early prototypes display not only good process compatibility, but impressive physical properties.
The room was packed for the presentation of Ellen Lee in materials and manufacturing research for Ford. While Ford has about 30 years of experience in 3D printing under its belt, Lee said the car maker is focused on going beyond the prototype level to the direct production of functional end-use parts. Recently, Ford developed a new, dedicated additive-manufacturing research program to explore the potential of new technologies to manufacture vehicle-ready parts.
Lee also revealed that Ford has partnered with Silicon Valley startup Carbon3D on using the company’s Continuous Liquid Interface Production (CLIP) technology. Last December, Ford began testing a pre-release version of Carbon3D’s first CLIP-based device. Ford says CLIP technology is allowing it to move more quickly from ideas to production. The automaker has already successfully applied the technology to current and future vehicle model designs, and is leveraging CLIP to research new automotive materials.
Carbon3D’s CLIP technology uses a tunable photochemical process instead of the traditional mechanical approach, which is said to eliminate the “shortcomings of conventional layer-by-layer 3D printing technology,” to rapidly transform 3D models into physical objects. CLIP carefully balances the interaction of UV light, which triggers photopolymerization, and oxygen, which inhibits the reaction, allowing objects to be continuously “grown” from a pool of liquid resin. Predictable mechanical properties allow for part creation across a range of needs for Ford vehicles including under the hood, interiors, and high strength/weight ratio parts.
Beyond the current vehicle applications, Ford has also been able to expand its own materials research because of CLIP’s gentle process and high-quality polymeric materials. To date, the team has tested several materials, including resins reinforced with nano-sized particles. Ford says it is eager to further investigate resin modifications for improved mechanical properties and to consider the creation of thermally and electrically conductive materials for future vehicle applications.
RENEWABLE AUTOMOTIVE MATERIALS
During her keynote presentation, Deborah Mielewski, Ford’ senior technical leader of sustainable materials and plastics research, talked about the auto giant’s focus on increasing the use of recycled and waste products in its vehicles. Ford’s biomaterials research program was founded in 2001. In 2008, Ford launched soy-based foam on the 2008 Mustang, and soy seat cushions and backs have now found their way into every Ford North American-built vehicle. The biomaterials research team continues to work on development of sustainable plastic materials, including natural fiber-reinforced plastics and polymer resins made from renewable feedstocks.
For the past few years, Ford has been working with forest-products leader Weyerhaeuser, Seattle, to develop a plastic composite material that uses cellulose fibers from trees in place of fiberglass or mineral reinforcements. This cellulose-reinforced PP replaces the fiberglass material typically used in the floor console armrest substrate—a structural piece within the center console armrest. Parts made from the new material are roughly 6% lighter and are being used for the Lincoln MKX.
“Do sustainable materials sell cars? Probably not,” Mielewski acknowledged. “Let’s be honest, people appreciate it, but it’s the not main driver. The advances of sustainable materials are that they protect the business from price fluctuation in the market. To me, we should have choices when it comes to materials—not just depend on petroleum.”