Reinforced Plastics magazine is reporting an exciting technological development in FRP fabrication, the development of integrated hinge technology for composites. In the article Your flexible friend: FRP with a hinge (Reinforced Plastics Jan/Feb 2016, p. 66), writer Liz Nickels relates the tale of two students at California Polytechnic State University (Cal Poly), Ann Livingston-Peters and Gabriel Mountjoy who, in 2011, came up with an idea for making integrated hinges in carbon fiber composite sheets. They were involved in a competition to design a high-efficiency vehicle. Their team was making a monocoque carbon fiber chassis, and the integrated hinge was a solution to reduce weight by having integrated doors.
Their patented hinge, which they call CF-lex, is made by removing the resin matrix along a discreet line in a sheet of hardened carbon fiber composite. Removal is accomplished with a laser. After laser ablation, the exposed fibers retain 78% of their strength. After 50,000 hinge cycles, the hinge retains 92% of it’s original strength. The exposed fibers can be protected with the application of a thermoplastic tape over the hinge, if desired. This process can also be used with glass fiber, and any other fiber with a sufficiently higher melting temperature than the matrix resin.
Although the article only hints at the architectural significance of this idea, it is still well worth reading to understand the technology fully.
Brief mention is made that, after laser ablation, the sheet can be bent at the hinge point and re-hardened at that angle by the application of additional resin. This means that sheets of carbon fiber (or glass fiber) could be formed much like sheet metal.
This opens up a range of possibilities. Such as:
- One-Offs: Casting composites on molds may be the most cost-effective way to make repetitive architectural elements, but for one-offs with flat surfces, laser-ablation folding could be far more practical.
- Form finding: It provides a way to explore a form and make changes to it quickly and cheaply.
- Prototypes and Mock-ups: It provides a way to prototype an FRP structural element and make a full-scale, testable mock-up.
- 2-D to 3-D: Both structural elements and architectural surfaces could be made from flat sheets of FRP, pre-hinged in the factory. That way they can be shipped flat to the job-site, saving a huge amount of space, and folded into shape on-site, origami-like, for final hardening. A complete shelter could probably be shipped on a pallet and dropped by helicopter anywhere on the planet. They could be assembled with no more tools than a mixing stick for the resin and a paintbrush to apply it (OK, perhaps a slight exaggeration). Such very compact shelter kits could be stockpiled in a minimal amount of storage space for preparedness against (for example) natural disasters that displace people from their homes, or crises that involve mass migrations of refugees.
You probably have a few more ideas, too.
Meanwhile, Livingston-Peters and Mountjoy, the Cal Poly student inventors, formed a company, Common Fibers, to commercialize their idea. They funded it on Kickstarter in 2014, and at the moment are focusing on small consumer items including several models of wallet, as well as non-hinged carbon fiber accessories like bottle openers and guitar picks. On their website, they state that a wallet’s material thickness is 0.02″, with a tensile strength of 1066 lbs., and a hinge tensile strength of 840 lbs. They have three different models of wallet for sale, starting at $99.00.
Common Fibers offers their wallets with an unusual warranty that says something about carbon fiber: For a wallet that fails (and they have a list of qualified fails), they will replace it free of charge for the first year, and after that, replace it for 50% of cost… forever (their phrase is “for the rest of eternity”).
Their wallet may have another long-term significance: it may be the forerunner of an ultra-lite shelter, or an architectural landmark building.
Keeping watching for further developments.
Images via Reinforced Plastics