CompositesWorld
Issue link: https://cw.epubxp.com/i/830100
JUNE 2017 24 CompositesWorld WORK IN PROGRESS downstream gripper, the gripper closes, firmly holding the cured profile while the die opens and again moves upstream to pull and cure the next section of material. is essential difference — a moving die — allows the material to be pulled around a curve. e result is a system that can continuously produce either a linear constant cross section or a constantly curved profile," Jansen says. As with conventional linear pultrusion, Radius-Pultrusion is a wet process. e fibrous materials are wet-out either by resin injection or in an open bath where local environmental regula- tions permit. TTI has vetted its system with a variety of composite mate- rials, including glass or carbon fiber impregnated with vinyl ester, epoxy, polyurethane, acrylate esters and others. Multiaxial fabrics are commonly incorporated, as well as veils, which are espe- cially useful for helping drape the material in the mold, Jansen says. What is needed in reinforcements for Radius-Pultrusion is material suited for what Jansen calls endless draping, to enable the material to follow the curve. "It must be flexible," Jansen says, noting that many woven materials are, indeed, flexible enough to be pulled around the curve. Five degrees of freedom For a constant curve in space, at least five degrees of freedom are necessary. "In addition to the horizontal x-axis of linear pultru- sion, curved pultrusion needs up to four additional axes," Jansen explains, naming the vertical y-axis, transversal z-axis and rota- tional axes (clockwise and counterclockwise), which would be added, for example, to make pipe (Fig. 1, p. 22). Jansen says TTI is now building machines that can produce linear profiles and — with some modification — curved parts with radii greater than 2,000 mm), incorporating the required additional axes of freedom. "Where the radius is parallel to the long axis, rotation and linear movement is vertical; and where the radius is parallel to the short axis, rotation and linear movement is horizontal," Jansen says. Typical parts, where the radius is parallel to the long axis, are bumper beams that are created with a vertical orientation of curve. Parts that can better be created with a horizontal curve include the thin reinforcement profiles for glass roofs on cars. For smaller-sized curved parts, with radii less than 2,000 mm, a different, custom design is offered. For these, the machine rotates about a central axis, which may be either horizontal or vertical. Parts for bicycle wheel rims are one example of what is possible on this type of machine. TTI, in fact, is in discussion with and making proof-of-concept carbon epoxy rim components for a bicycle manufacturer interested in the potential of Radius-Pultru- sion. e part radius here is about 300 mm. "Every kind of profile that is somehow curved can be manufac- tured by pultrusion now," says Jansen. Licensing the process In addition to producing parts for customers on its Radius- Pultrusion machines, TTI is licensing the technology to others. "We are currently developing new pultrusion lines together with FIG. 5 Autocomposites pultruded bumper beams? This graphic rendering depicts licensee Shape Corp.'s (Grand Haven, MI, US) Radius-Pultrusion system, which will be used to produce curved automotive bumper beams. Source | Shape Corp. Read this article online | short.compositesworld.com/CurvedPult