CW Blog

By: Jeff Sloan 14. February 2019

A change in the wind

When I joined CompositesWorld as editor-in-chief in the fall of 2006, I was coming off of a 10-year stint as editor and eventually publisher of a trade publication that served the injection molding industry. As I transitioned to my new job at CW, I anticipated some modest crossover in materials and manufacturing concepts between injection molding and composites. Both industries are polymer-based, and there are principles of robust injection molding manufacturing that, I assumed, must have application in composites manufacturing as well.

My assumptions, of course, turned out to be wrong. Injection molding is a machinery-intensive, fast-cycle process that uses thermoplastics almost exclusively. The name of the game is speed (measured in seconds), consistency, repeatability and tight, highly automated process control. In composites, I discovered a vast and complex world composed of multiple fiber types, fiber formats, resin types, tooling types and process types. And although machinery is important in composites fabrication, it is not the centerpiece of fabrication. Further, the highly engineered, multi-ply, quasi-isotropic nature of composites manufacturing depends, in many cases, on touch labor of the type that would be unheard of in injection molding. 

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By: Dale Brosius 11. February 2019

Composites recycling — no more excuses

In April 2016, I authored a column titled “Can we make recycled carbon fiber sexy?”. It was written after I had seen a roof panel on a BMW i8 at the North American International Auto Show in Detroit that was made from a visible, clear-coated carbon fiber mat, recovered and repurposed from cuttings in BMW’s composites manufacturing process. It demonstrated significant forward thinking at the time, as all other examples of visible carbon fiber on display at the show were woven fabrics, yielding the classic carbon fiber “look” under their clear finishes.

A lot has transpired since then, as various composites recycling technologies have matured and spawned multiple entrants. Composites recycling has also attracted investment from venture capital funds as well as strategic investors, such as Hexcel (Stamford, CT, US) taking an equity position in Carbon Conversions Inc. (Lake City, SC, US) in 2016, and the December 2018 announcement of Mitsubishi Corp. (Tokyo, Japan) taking a 25% stake in ELG Carbon Fibre Ltd. (Coseley, UK). Perhaps most significant is the growing list of end-use applications incorporating recycled composite materials, from manhole covers to park benches to materials for 3D printing, among others.

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Composites have been used in fire resistant applications for decades. Generally, inorganic fibers (e.g., glass, carbon, basalt, ceramic) and inorganic matrix materials (e.g., ceramic/carbon, metals, polysialate/geopolymers) do not burn and most can withstand high temperatures. However, when most organic fibers and polymer matrices are exposed to high temperatures and fire, they will decompose into:

A composite’s fire performance is measured by a variety of characteristics, including:

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My latest blog, about HIA Velo bicycles, concerned the use of high molecular weight polypropylene (HMWPP) combined with carbon fiber for more durable bicycle frames. But there’s more to cover on this topic: bicycle rims (wheels) that combine carbon and HMWPP for greater toughness. I recently had the opportunity to speak with Ray Scruggs, the founder, owner, and product designer of Derby Rims LLC (San Anselmo, CA, US). The company is named for Scruggs’ nickname (derby), which came from his participation in friendly mountain bike gatherings, or derbys, in the California mountains.

Scruggs began designing and testing carbon fiber bicycle rims in 2012, and sold his first mountain bike rims, which were wider than any available at the time, in 2013. Says Scruggs, “My carbon fiber rim designs had much improved thicker, more durable upper rim walls and tire retention safety over existing carbon rims.” He adds that advanced riders recognized the advantages of improvements in width, durability and safety. Scruggs continued investing all proceeds from rim sales back into the business, while continuing his day job testing and developing business software. He explains that he filed patent applications for new designs for self-protection but adds “My designs were immediately closely copied by nearly every carbon fiber rim brand.”

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A research program in the UK is attempting to achieve a fundamental step-change in the composites industry. HiPerDiF (High Performance Discontinuous Fibre) project, which began in December 2017 and runs through 2020, is a program funded by the UK’s EPSRC (Engineering and Physical Sciences Research Council: https://gow.epsrc.ukri.org/NGBOViewGrant.aspx?GrantRef=EP/P027393/1 ) that is exploring an alternate way of producing high-performance carbon fiber composites: start with discontinuous, rather than continuous fibers. The program, led by Professor Ian Hamerton of the Bristol Composites Institute (ACCIS) at the University of Bristol, has an impressive roster of project partners, including Airbus, Toyota, BAE Systems, ELG Carbon Fibre Ltd., Hitachi Chemical Co. Ltd., and several composite material suppliers including Solvay and Hexcel.

My colleague Ginger Gardiner has already blogged about this topic, describing several US entities with the same idea (here’s the link: https://www.compositesworld.com/blog/post/sustainable-inline-recycling-of-carbon-fiber). And even earlier, I wrote an article in CW about stretch-broken, discontinuous carbon fiber as a means of faster manufacturing: https://www.compositesworld.com/articles/aligned-discontinuous-fibers-come-of-age. The HiPerDiF researchers argue that in order to increase composite part production volumes, we need to simplify and automate our manufacturing processes. And, if greater production volume means using more carbon fiber, we also need to employ recycling processes to recover the fiber, and methods to reuse the fiber, while retaining its mechanical properties and economic value. In other words, develop a high-volume method that can readily, as the group says, “remanufacture” recycled short fibers and produce parts with mechanical properties comparable to continuous fibers, with those parts in turn (if coupled with a thermoplastic matrix) getting recycled several times (here’s a link to a paper on the topic: https://www.sciencedirect.com/science/article/pii/S1359836818301896?via%3Dihub).

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