Analysis and evaluation of the effects of residual stresses on the damage evolution in intrinsically manufactured hybrid materials

Due to their weight-specific high strength and stiffness fiber-reinforced plastics (FRPs) have attracted great interest in the lightweight sector. Besides the solitary use of these FRP composites, the central focus is on application of hybrid structures. Time and cost-efficient production can be realized by process induced bonding of metal and FRP. Such kind of intrinsic hybridization allows to significantly reduce the total number of processing steps. However, the interface between metal and FRP is the weakest link in these hybrids, as different thermal expansion coefficients of fiber and metal lead to evolution of residual stress upon cooling from processing temperature to room temperature. At critical areas of the component, these stresses can be relieved through localized delamination.

Therefore, the present study focusses on the effects of residual stresses on damage evolution in intrinsically manufactured hybrid FRP-metal structures. As a first step methodological questions concerning the experimental residual stress determination in layered composites as well as effects of materials and process parameters on the resulting residual stress distributions were assessed. Subsequently, effects of manufacturing-induced residual stresses on the behavior of hybrid materials under mechanical loading, particularly damage evolution under static and cyclic loading, are investigated.