No abstract

Among engineering materials today continuous fiber reinforced polymers (FRP) show some of the highest stiffness and strength to weight ratios. To rival the traditional manufacturing methods of continuous FRP many investigations have sought to combine the outstanding mechanical performances of these materials with the freedom in design and the economic benefits of additive manufacturing (AM). This paper focuses on the fiber placement strategies and their interaction with Selective Laser Sintering (SLS) specific machine features. The goal is to develop and conduct test series to gain a deeper understanding of how the process, the polymer, and the reinforcement fibers interact. For this investigation different patterns of glass fiber rovings are embedded into specimens made from PA 12 on a Sintratec Kit printer. The rovings are put up onto a frame in varying patterns to be able to relate fiber tension and curvature as well as the stack height of intersecting rovings to the quality of embedding. Additionally the time of placement, the clamping and the interaction of the fibers with the recoater have been investigated. Based on these results an SLS printer with automated continuous fiber implementation will be developed in the future.

An innovative production processes for manufacturing rotationally symmetric FRP-metal components, such as drive shafts or tie rods, is the rotational molding process. In the course of this process, a dry fiber preform and metallic load-introduction elements are inserted into a two-piece mold and subsequently clamped into a spindle. The matrix is injected directly into the rotating mold. Due to the arising centrifugal forces, the preform is impregnated and the component cures under rotation. In comparison to conventional joining processes, such as adhesive bonding or bolt connections, the metallic components as well as the FRP part are intrinsically joined during the forming process. A downstream joining process is not required. The joint is based either on the adhesive property of the matrix system or on a form-fit geometry with undercuts. The paper addresses the production and tensile testing of tie rods. Different rod geometries and different surface treatments, including sandblasting, knurling, and arc spraying, are compared and evaluated.