Dow Automotive Cuts Composite Cycle Time to 60 Seconds

Ann R. Thryft

March 20, 2015

4 Min Read
Dow Automotive Cuts Composite Cycle Time to 60 Seconds

At the JEC Europe 2015 composites show in Paris March 10-12, many companies showcased their carbon fiber composites and related products, especially for high-volume automotive manufacturing. Last year, Dow Automotive Systems introduced commercial availability of its ultra-fast, under-90-second molding cycle time VORAFORCE 5300 matrix. This year, the company announced a new record-breaking, under-60-second molding cycle time for the epoxy resin matrix, with 30-second times coming later this year.

MORE FROM DESIGN NEWS: Slideshow: New Carbon Composites for Production Car Volumes

Dow Automotive's global strategic marketing manager Peter Cate, and senior R&D manager Rainer Koeniger, gave a Tech Talk last week at JEC Europe on the new cycle times for the matrix and its processes. The commercial product was initially aimed at high-pressure resin transfer molding (RTM) for making structural parts for high-volume car production. VORAFORCE 5300 with the shorter under-60-second processing time is aimed at both RTM and wet compression processes, Cate told Design News.

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The shorter times have come through yet more work on chemistry, Cate said. Dow's been tailoring the material and the process to address its OEM car maker customers' goals for several years, as we've been reporting since 2012. In this slideshow, we detailed how company engineers achieved fast cycle time while the material was still in development by optimizing carbon fiber and resin chemistry for stiffness and strength, while also withstanding thermal, moisture and aging cycles, along with sustained very low processing viscosity and low moisture absorption.

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The 90-second commercial matrix had a processing viscosity of 15 millipascal seconds (mPa.s), but that's now been pushed down to 10 mPa.s, which is four to five times lower than previous competitor's benchmarks, Cate told us. The resin's lower viscosity means faster infusion with less movement of the fibers and better wet out. It also allows longer infusion times. These enable complete wetting and filling of the large structural composite parts sought by automotive OEMs, who want composites both to enable lighter weight, and to consolidate smaller parts into larger complex ones to save cost and improve reliability. Cutting composite part costs makes them just that better of an alternative for mass production, and a relatively cost-comparable one, to multiple steel parts welded together.

In RTM, the dry preform is put into the tool, the tool is closed, and the preform is infused with resin. Wet compression splits up the infusion process: resin is applied to the dry preform outside the tool, which is then closed for curing. In that process, there's very little flow, since resin is already in place. "In wet compression, the infusion and flow parts of what goes into total cycle time in an RTM tool are eliminated, and the molding step is really the curing step," said Cate. "This is important because the press is now doing only what it's really best at doing: curing resin as fast as possible. With RTM, we can get the process down to less than 60 seconds. But in wet compression, cycle time can go down to 30 seconds, and the tool can run hotter, so the part cures faster." This isn't to say that everything will move to wet compression, though. For instance, complex parts tend to be made with RTM, while simpler parts tend to be made with wet compression.

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For some applications, automotive suppliers also want higher thermal performance than VORAFORCE 5300's glass transition temperature of 120C, Cate said. So Dow Automotive is developing two new grades of VORAFORCE that aren't commercially available yet: 6300, with a glass transition temperature close to 150C; and 7100, with a glass transition temperature of about 170C. These new higher-temperature grades were developed for specific application needs, such as a higher temperature in normal operations or in automotive assembly during the e-coat bake stage. All three grades are designed to work with both RTM and wet compression, and need no post-cure. Post-cure for the 7100 formulation, though, allows a glass transition temperature of just under 200C.

Ann R. Thryft is senior technical editor, materials & assembly, for Design News. She's been writing about manufacturing- and electronics-related technologies for 25 years, covering manufacturing materials & processes, alternative energy, machine vision, and all kinds of communications.

About the Author(s)

Ann R. Thryft

Ann R. Thryft has written about manufacturing- and electronics-related technologies for Design News, EE Times, Test & Measurement World, EDN, RTC Magazine, COTS Journal, Nikkei Electronics Asia, Computer Design, and Electronic Buyers' News (EBN). She's introduced readers to several emerging trends: industrial cybersecurity for operational technology, industrial-strength metals 3D printing, RFID, software-defined radio, early mobile phone architectures, open network server and switch/router architectures, and set-top box system design. At EBN Ann won two independently judged Editorial Excellence awards for Best Technology Feature. She holds a BA in Cultural Anthropology from Stanford University and a Certified Business Communicator certificate from the Business Marketing Association (formerly B/PAA).

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