Globe Machine Manufacturing Co. (Tacoma, WA, US) told CW in an exclusive interview at JEC Europe 2015 (March 10-12) that it is making progress on next-generation composites processing concepts for even faster cycle times. Known for its trademarked RapidClave machines capable of sub-eight minute cycles (read the CW story here), the company says it is now close to trialing a thermoplastic work cell process for production of structural automotive parts, said president Calvin Bamford, Jr.
“We are employing a two-pronged approach,” he stated. “We have fast-cycle technology for thermosets, and now will have the ability to quickly and reliably process thermoplastic materials.” While no specific details about the thermoplastic work cell or machines are available yet, Bamford did say that the process is designed around unidirectional tape, not consolidated thermoplastic prepreg sheet material based on woven fabrics, and will involve consolidation pressure and some combination of water and hot air for heat transfer. This new, third-generation process technology should be unveiled sometime this year.
Bamford and Globe’s automotive composites expert Gary Lownsdale said that one of the key challenges encountered in development of very fast heating and cooling cycles is “dynamic viscosity” of the resin. Lownsdale explains that at ramp rates as high as 60°C per minute, required for automotive rates, resins can behave very differently than they do in the deliberate, traditional autoclave ramp rates of a few degrees over several minutes. The resin can actually shear or undergo other physical flow changes not related to chemistry.
To address concerns about dynamic viscosity, significant testing of carbon fiber-reinforced coupons has been undertaken throughout the RapidClave’s development. Bamford reports that results are in on parts made with a classic, well-qualified aerospace epoxy system. Parts were produced by the RapidClave and a traditional autoclave, and mechanical results show that the fast-cycle parts had mechanical performance comparable to the autoclaved parts.
“This proves that even at the very high heating rates, aerospace resins can perform, with no property degradation,” asserts Bamford. “We have not yet found the practical limits of most resin systems!” Lownsdale points out that by testing these established resins and proving they work in Globe’s accelerated process, customers can used already-qualified, established materials, saving time and money. When asked if aerospace parts are on the horizon, Bamford said Globe’s processing concepts can be scaled to any size, even to parts like wing skins. “For the aerospace industry, we’re looking to take some of the good technology from our automotive experience and apply it to novel work cells to meet the growing demand for automation.”