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Processing technologies for carbon fiber-reinforced composite molding were at the fore at the recent IPF 2014 near Tokyo, with leading injection molding machine builders promoting their expertise in the field.

One of the more impressive and innovative technologies on show could be found at the JSW (Hiroshima, Japan) stand. As reported earlier, the company was showcasing a composite molding technique that employed a flexible semi-preg: a flexible carbon fiber fabric powder impregnated with with polyamide (PA) resin.

Japanese injection machine builders are hoping that lower-cost carbon fiber composite processing technologies will allow these composites to penetrate beyond Toyota's Lexus LFA high performance supercar (base price: $375,000), shown here at Composite Materials & Molding System Expo-FRP & CFRP & FRTP, that was part of the IPF Show. Flexible, powder-impregnated semi-preg enables partial back-molding of complex deep-draw parts. Multiple sheets of semi-preg are first trimmed from a roll of the fabric. At IPF, eight layers of prepreg were employed in the prototype part being molded. These sheets are stackded and then direct-formed via press-molding utilizing and heat and cool tool to form a rigid carbon fiber-reinforced component. This part can then be selectively overmolded with a frame rather than having to back-mold the entire pre-preg as is common with standard hybrid processes.

The JSW technology was demonstrated on a JT70RAD-110V-CFRTP hybrid molding system centered on a vertical injection press at IPF. The injection cycle time was 40 seconds. The injection-molded frame was comprised of 15wt% carbon fiber-reinforced PA 6, while the semi-preg was comprised of 60 volume% carbon fiber with the remainder comprised of PA powder and can be deep-draw formed. Manufactured by electrostatic coating of the carbon fiber with PA powder followed by IR heating, the semi-preg boasts a void ratio of just 0.5%.

JSW also demonstrated the application of its Melt Transcription Molding Process, debuted at IPF 2011, to molding of CFRTP. Firstly, the molten polymer is coated onto to the tool as per the standard process. Multiple carbon fiber sheet are then laid in to the tool, followed by pressinf and impregnation. "The advantage with this process the carbon fibe sheets can be laid in a random orientation," says Shigeki Inoue, General Manager of JSW's Hiroshima Research Laboratory. "Random orientation is preferable for parts with complex shapes," he notes.

Also promoting carbon fiber composite processing was Toshiba Machine (Tokyo), who brought a larger version of its LFormer "on-line blend injection molding machine" to IPF 2014. The LFormer debuted at IPF 2011 in the form of a 100-tonne press molding a motorcycle part. This year, a 550-tonne machine was on show.

The LFormer molds long-fiber compounds by feeding multiple strands of continous filament (carbon fiber, glass fiber, or potentially both) directly into the melt flow in a plunger-type injection unit. As a result, the fiber length in the final part averages around 5 mm. At IPF 2014, Toshiba chose to use a combination of glass fibers and carbon fibers to ensure proper fiber dispersion throughout the larger part, a 190 x 230-mm transmission cover molded from PA 6 with a shot weight of 430 g. Carbon fibers 7 microns in diameter are hard to disperse in such a large part, while glass fiber dispersions is good and the latter tend to piggyback carbon fiber throughout the matrix. The reinforcement ratio was 15% glass fiber/15% carbon fiber.

The transmission cover is 50% lighter than its aluminum diecast equivalent. Further, it was molded in a cycle time of 90 seconds.

Toshiba also brought back its 1oo-tonne version of the LFormer to IPF 2014, but this time mated it with a thermoplastic carboin fiber prepreg that was heated with a near-infrared heater before insertion into the mold. Sample "pillar connecting" parts were being molded in a cycle time of 60 seconds using carbon fiber-reinforced PA resin.

Toyo Machinery & Metal Co. (Akashi, Japan).was also showing a composite solution with continuous carbon fiber sheet being overmolded with long carbon fiber-reinforced polypropylene. The carbon fiber sheet is heated with an infrared heater in the mold prior to processing. One sheet can be heated while the other is being overmolded in the rotary type clamping unit, which was cycling at 40 seconds at IPF and molding a 28-gram test piece. Toyo uses its V&D screw in the 80-tonne vertical press to improve fiber dispersion while maintaining fiber length.

Sodick (Kaga, Japan) also demonstrated its capabilities in long fiber molding with its GL60(32) plunger press molding a 60% long glass fiber reinforced polyamide wrench. The 32-mm diameter screw employed in the machine ensures initial fiber length of 7 mm in the plastic compound still remains at around 2 mm in the finished product. "We see more potential for development of small long fiber reinforcen parts such as drill bits and printer shafts," says Sodick Marketing Center Executive Officer Kazuyoshi Taniguchi. "Previously, small parts were difficult as small screws tend to break down the fibers more but we've been able to overcome this through screw and barrel modifications."

Mitsubishi Heavy Industries Plastic Technology (Nagoya, Japan) was highlighting the capability of its machines to process long fiber materials with good fiber dispersion and minimal degradation in length. Real world examples of such components molded with its machinery were the radiator core support for the Nissan Fairlady Z, molded from long fiber polypropylene by Calsonic Kansei on a 2000MM III-340 injection machine, and a similar component for the Nissan V37 Skyline.

A Mitsubishi 3500MMV-470 injection press is also employed by Hitachi Chemical to mold the inner (PP+LGF) and outer (PP) parts for an all-olefinic liftgate for the Nissan X-Trail. This is the same liftgate employed in the Nissan Rogue made and  sold in North America. The molding is handled by Magna International Inc. (Aurora, ON).

"There's still a long way to go for long fiber compounds in Japan,:" says Yasuo Honda, General Manager, Sales Department, at Mitsubishi. But developments at IPF 2014 certainly proved the industry is headed in the right direction.

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