Bent pultrusion—a method for the manufacture of pultrudate with controlled variation in curvature

Variously known as “Bent pultrusion”, “3D pultrusion”, or “Post-Die Manipulation”, this is a method of pultrusion where the cure process takes place outside the die. This results in very low pulling forces and the ability to manipulate the shape of the pultrudate during formation. In the normal pultrusion process continuous thermoset resin coated fibres are pulled through a long heated die. Since the resin is cured within the die the pulling force required could be significant, consequently current process machines are large and expensive. The finished pultrudate is also limited to continuous straight profiles of constant cross-section. In the feasibility study work described in this paper, the process of curing relies primarily on irradiating the resin-coated fibres with ultra-violet (UV) light, as the profile exits the die. The die therefore, is only required to impart a profile, and strip excess resin from the fibre/resin bundle. The pulling force is thus very much reduced lowering the capital cost of the plant. The pultrudate can be manipulated after it exits the die and before the resin matrix has fully cured to produce a product with controlled variation in curvature.