Investigation of asymmetrical fiber metal hybrids used as load introduction element for thin-walled CFRP structures

Abstract

Due to the industrial success of fiber reinforced plastic (FRP) light-weight components, the demand for joining methods suitable for FRP increases as well. Conventional joining elements like rivets and screws or simple clamping are designed for an application in conventional isotropic materials such as steel or aluminum. Therefore, by design these joining elements do not consider characteristic FRP properties such as the orthotropic (fiber) or the setting behavior of matrix materials that are subjected to a constant load. Thus, without any FRP specific adjustments, conventional joining elements will, in most cases, lead to poor results and an inferior joint. Hence, this investigation presents the concept of a layered local metal-hybrid area that can be used as a load introduction element, the "Multilayer-Insert". The design aspects of the hybrid area are discussed for several stacking options. Furthermore, the sensitivity to geometrical design variables and asymmetrical stackings are investigated by a simplified two-dimensional finite element model. The deduced parameter relations are discussed in the context of an application in an automated fiber placement process in order to formulate recommendations for the geometrical parameters.