CompositesWorld
Issue link: https://cw.epubxp.com/i/576646
OCTOBER 2015 106 CompositesWorld APPLICATIONS Carbon fiber/PET saddle tree features intralaminate heating element REFORMABLE COMPOSITE EQUESTRIAN SADDLE › The efectiveness of LaminaHeat LLC's (Greenville, SC, US and Dorset, UK) PowerFilm and PowerFabric materials in heated composite tooling and structures was recently demon- strated in a very big way, via an 18m long carbon fber (CF) composite tool used by Norco GRP Ltd. (Poole, Dorset, UK) to cure the tips of Blade Dynamics' (Southampton, UK) 75m long composite blades for 6-MW ofshore wind turbines (see "Learn More"). PowerFilm, a thin (100 microns thick) layer of randomly oriented carbon fiber insulated with a polymer and incorporating copper contacts, converts electricity into heat so efficiently that it can generate up to 10 KW/ m 2 — roughly the same heat as three gas fires — from only 1m 2 of material. In fact, PowerFilm converts with 99% efficiency vs. 80% for gas flame, according to technology developer Peter Sajic. But before its prowess was demonstrated in processing turbine blades, PowerFilm was trialed in carbon fiber/ polyethylene terephthalate (PET) composite structures for equestrian saddles, providing a solution that could have far-reaching applications, from sporting goods to medical devices. Sajic had friends involved in horse training and was aware of their issues with fitting saddles. "One of the biggest problems ... is that the shape of the horse changes as it grows and matures, just like in people," he explains. The saddle must be sent back to the saddlemaker, who adjusts its shape to better fit the horse, to prevent chafing, discomfort and potential injury. This must be done at least twice annually at a cost of roughly £350 (US$550) each time. Sajic says the saddlemaker must first send someone out to measure the horse with a special gauge. The saddle is then disassembled and a hydraulic ram is used to open the width of the saddle tree, or frame structure, principally in the neck area. "Though the gauge measurement is used to guide the widening," says Sajic, "it is still, typically, a trial-and-error process." Sajic proposed a PowerFilm-enhanced composite alternative that enables a saddle to "grow with the horse." "With our system," Sajic explains, "you have the saddle on the horse and simply connect a power source via a plug at the rear of the CF/PET saddle tree." The latter heats up to 120°C-140°C (the leather acts as an insulator, so the horse feels about 25°C). A saddlejack is used to widen the neck area of the now-pliable laminate until it matches the horse's shape. "We designed the PowerFilm to hit 120°C in 2 minutes," explains Sajic. "It uses a 24-volt DC power source, so it's very safe." The CF/PET saddle tree is made using 12K CF tow commingled with linear PET (LPET) fiber. The latter enables lower processing temperatures vs. normal PET. The commin- gled tows are woven into fabric by Carr Reinforcements (Worsthorne, UK). The dry fabric is then hand layed onto a metal tool, with the PowerFilm and electric wiring to the power socket embedded within. The layup is then vacuum bagged, heated to 190-200°C and cured under vacuum for 20-30 minutes. After demolding, it's trimmed to size and ready to form the structure for the saddle. The PowerFilm is an efficient solution. "It supplies 10 kW/m 2 from a 0.004m 2 piece of film that is 200-250 microns thick and needed only at the neck," says Sajic. He notes there are 200 shapes that can be used to customize saddle trees, "but with our system, you only need, maybe, five or six generic shapes, and then simply heat them to tailor and match the horse you're riding." LaminaHeat's other PowerFilm applications include de-icing of wind blades. Sajic notes, "We've demonstrated a proactive system that prevents ice from forming, using a very low-mass insert [20 g/m 2 ] embedded into the glass laminate." "There are companies spending millions on carbon nanotubes," says LaminaHeat's VP sales and marketing for North America Marc Anderson, "but we have a low-cost, efficient solution that works now." Read more about the 6-MW blade tips online in "Heated Composites" | short.compositesworld.com/HeatComp Source (both photos) | LaminaHeat