The use of lightweight components increases the payload of different systems and reduces the energy consumption of moving vehicles.
One innovative production process for manufacturing rotationally symmetric FRP-metal components, such as drive shafts or tension and pressure rods, is the rotational molding process. For the rotational moulding, a dry fibre preform together with two metallic load-introduction elements is inserted into a two-piece mould and clamped in a spindle. The rotation process is then started and the matrix is injected directly into the rotating mould. Due to the centrifugal forces that occur, the preform is impregnated and the component cures under rotation. The impregnation process is divided into two phases. It begins with a radial impregnation followed by the axial impregnation of the overlapping area between the metallic load introduction element and the preform. In comparison to common joining processes, such as bonding or screwing, the metallic components and the fiber-reinforced plastic part can be intrinsically joined during the forming process. The joint can based on the adhesive property of the matrix system or on a form-fit geometry. This saves production time and cost compared to conventional joining processes. Since additional joining process are no longer necessary, production time can be reduced.
In order to fully control the impregnation process, an analytic impregnation model which based on Darcy’s law model is developed. By use of this model the impregnation time can be calculated, when permeability and viscosity are given. The analytic impregnation model is validated through an experimental test series. For the production of hybrid form fit geometries, the preform needs to have a near-net-shape geometry. This is important because a poor contour accuracy will lead to wrinkles when closing the mold. Hence, a special preforming machine for the corresponding forming step is designed and optimized.
To increase the load transfer between metallic load introduction element and CFRP-part, finite-element simulations are conducted to optimize the geometry of the hybrid components. The results are compared to experimental tensile test results. In addition various mechanical surface treatments are compared to increase the adhesive bond between metal and CFRP. Furthermore computer tomography and microscopy analyses are conducted to determine the fibre volume, the pore content and the interface shape.