CompositesWorld
Issue link: https://cw.epubxp.com/i/866813
NEWS 73 CompositesWorld.com SMC Renaissance, Part 2 needed, but because the formal project has come to an end, that work will have to wait until additional funding and new partners can be found. Other research on the agenda includes evaluating additional filler systems as well as unfilled structural systems with higher reinforcement levels vs. the preliminary formulations. Park notes that the current PUR SMC systems FPC tested are at the practical limits of glass content (60 wt%). "Carbon fiber-reinforced PUR or epoxies or even vinyl ester are promising because part and mold design know-how for SMC are already well understood, and the process allows you to do near net-shape forming of a 3D, quasi- isotropic part at very low scrap rates relative to other carbon fiber composite molding processes," he adds. Connolly says that FPC and Huntsman did additional screening work after the formal study ended to evaluate PUR with 50K carbon fiber tow from Zoltek: A Toray Group Co. (Bridgeton, MO, US) in the D-SMC process. He says the work looks very promising, with the carbon/PUR SMC showing comparable or somewhat better tensile and flexural strength than large-tow carbon fiber/ VE SMC. Demold times were as low as 2.5 minutes at 130°C and 2 mm part thickness to yield a resin T g of ~125°C. More work is underway to evaluate molding of 3D designs, conduct extended freezer-storage studies and further explore impact testing. "We'd love to cooperate with interested companies for glass or carbon fiber [SMC] technology development, as there is only so much technology push we can do on our own," Connolly notes. "We need some pull now. We don't care where the pull comes from, but the most obvious choice would be from the molder/compounder level." Preliminary work suggests that PUR SMC may find a fit in applications that require greater durability and toughness. Interesting research also is underway in the epoxies arena. VE, itself, is synthesized from an epoxide, so epoxy-modified VEs and VE/UP blends have been available for some time. However, resin supplier Hexion Inc. (Columbus, OH, US) has recently commer- cialized a 100% epoxy grade specifically designed for automo- tive SMC. In addition to high mechanical properties, another advantage of epoxy SMC is that it is inherently compatible with epoxy prepreg: e two products can be co-molded to achieve a "tailored" composite part. e new system — EPIKOTE resin TRAC 06605 and EPIKURE curing agent TRAC 06608 — is said to be a low-viscosity formula- tion with good flow and fiber-wetting characteristics, specifically modified for the SMC process. It can be supplied with an internal mold release agent (HELOXY TRAC 06805) to expedite demolding. Structural SMC/prepreg hybrid A collaborative R&D; project between Ford Motor Co. (Dearborn, MI, US) and Magna Exteriors (Troy, MI) has led to development of an innovative prototype composite subframe. An important element of the car chassis, the subframe provides attachment locations for both engine and wheels while also contributing to rigidity and crash management. Compression molded of hybrid carbon SMC plus carbon prepreg, the part reduces mass by 34% and part count from 45 to 6 vs. the previous stamped steel assembly. The two composite subcomponents and their four metallic inserts are assembled via both adhesive bonding and structural rivets. Prototypes are reportedly undergoing vehicle-level testing at Ford. Source | Magna Exteriors