High-Performance Composites

NOV 2014

High-Performance Composites is read by qualified composites industry professionals in the fields of continuous carbon fiber and other high-performance composites as well as the associated end-markets of aerospace, military, and automotive.

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N O V E M B E R 2 0 1 4 | 2 7 N O V E M B E R 2 0 1 4 | 2 7 a vehicle when there is a compelling economic business case. The take-away? New, lightweight steel alloys have cap- tured the attention of OEMs and will increase the competitive pressure com- posites face in the automotive market to a greater degree than many realize. A wealth of technology Technical sessions revealed a wealth of new revelations from composites research. A recurring theme was high- rate-capable processing methods for thermoset materials. Koichi Akiyama, group leader for automotive compos- ites material development group of Mitsubishi Rayon Co. (Tokyo, Japan), described ongoing development of his company's prepreg compression mold- ing (PCM) technology, in which carbon fber prepreg material, preformed in a press-forming process, is molded in a high-speed compression press. Akiyama reports that prepreg cure is in the three- to fve-minute range, and work contin- ues to reduce it further. PCM reportedly yields a Class A fnish and can be modi- fed for comolding with other materials, such as SMC. Akiyama described the re- design and processing of a carbon fber decklid for the Nissan R35 GT-R , using PCM. On display at the show, the part is 40 percent lighter than the aluminum part it replaced. Although state-of-the-art epoxy systems can cure in as little as two minutes, high-volume automotive ap- plications require production output of about 1,000 parts per day, which equates to a one-minute cure time over two shifts. Roman Hillermeier, transpor- tation technology manager, Momentive Specialty Chemicals Inc. (Columbus, Ohio), presented a method capable of producing carbon fber-reinforced "crash box" components via RTM at that rate, using its fast-curing EPIKOTE epoxy system and multicavity tooling. (Crash box components attach to the front-end module of the body-in-white, absorbing energy in event of a crash.) The carbon fber preforms for the parts were continuously braided on a man- drel, cut and then placed directly into a multicavity mold. At nine parts per mold, given an average cure cycle of two to three minutes, the process can pro- duce 1,000 parts in 10 hours — six hours short of two shifts. Hillermeier asserted that a cost objective of €5/kg of saved weight could be achieved by using glass or lower-cost, heavy-tow carbon fber. Sebastian Schmidhuber, lead R&D engineer at KraussMaffei Technologies, explained the nuances of several high- pressure RTM (HP-RTM) processes. One of the newest, Surface RTM, is capable of producing ready-to-paint carbon fber exterior parts out of the mold. In this two-step process, a preform is placed in the mold and impregnated with a ma- trix resin via compression RTM. Next, the mold is opened slightly and poly- urethane is introduced into the cavity through a side injector in the mold. The mold is again compressed, creating, af- ter cure, an overmolded Class A surface. In the area of sheet molding com- pound (SMC) for body panels, Ashland Inc.'s (Covington, Ky.) Michael Sumner, group leader for SMC, gel coat and ma- rine resin, in the composite polymers Global Technology Organization, de- scribed that group's design-of-experi- ments project to boost the mechanical properties of its 39 percent glass-flled, 1.2 density Class A SMC. Its goal is a minimum 20 percent improvement by replacing the material's unsaturated polyester resin (UPR) with differing amounts of vinyl esters. Researchers found that a 50 percent blend of a par- ticular vinyl ester with a new, low-profle additive and reactive toughener yielded up to a 40 percent improvement of tar- get mechanical properties without a ma- jor compromise in surface fnish quality. SMC also was the topic for AOC's (Col- lierville, Tenn.) Jeff Klipstein, a closed mold technical service specialist, who described his company's new low-den- sity (1.2) SMC that reportedly has prop- erties equivalent to standard SMC at 37 percent lower mass, and with a Class A surface. This is tricky, explains Klipstein, because adding more glass enhances mechanical properties but tends to de- grade the molded surface quality. The new, low-density formulation of poly- ester and glass fber is reportedly com- petitive with aluminum in terms of cost and weight savings. Work is ongoing to further reduce density while maintaining properties and surface quality. Thermoplastic autocomposites Thermoplastic composites were featured in several sessions. One of the chal- lenges for thermoplastics in automotive applications is meeting part stiffness requirements at elevated tempera- tures — typically 90°C/194°F. Du- Pont's (Wilmington, Del.) Paul Kane, who leads Du- Pont's Performance Materials North America advanced development auto- motive lightweight- ing solutions team, presented a re- view of high glass- t r a n s i t i o n - t e m - perature (high-T g ) polyphthalamides (PPAs) and their use as an overmolding resin with stamped, continuous glass fber/polyamide in- serts. Kane reported that at 90°C/194°F, a 50 percent glass- reinforced PPA with a T g >100°C/212°F has almost twice the modulus of a 50 percent glass-flled PA 6/6. Kane reported results of a study that found crossmember beams compris- Battery-case case study Keynote speaker Kestutis "Stu" Sonta, senior materials engineer, General Motors Co. (GM, Detroit, Mich.), revealed the novel composite design developments that preceded production of the complex, two-piece battery enclosure now aboard GM's Chevrolet Spark (see the photo and caption on p. 29). SPE ACCE Scholarship winner A winner of one of two SPE ACCE Scholarship Awards, Fatimat Oluwatoyin Bakare was awarded $2,000 in honor of her proposal for "Synthesis of Bio-Based Composites with a Lactic Acid Based Thermoset Resin from Lactic Acid and Allyl Alcohol." Originally from Nigeria, Bakare is working on her Ph.D in materials science/polymer engineering at the University of Borås (Borås, Sweden). Michael Connelly, product manager at Huntsman Polyurethanes (Auburn Hills, Mich.), presented the award. Source: SPE ACCE Source: SPE ACCE

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