Stamp forming of steel-based fibre metal laminates

This paper investigates forming and failure modes of a fibre metal laminate (FML) system based on steel- and glass-fibre reinforced polypropylene composite material constituents. A hemispherical punch was used to perform stamp forming on this hybrid material at different blank preheat temperatures and blank holder forces. The evolution of surface strain during forming was captured and analyzed with a real-time three-dimensional photogrammetric measuring system. An increase in preheat temperature leads to elimination of composite failure and rises fibre trellising in the middle layer. At these temperatures, inter-ply delamination between FML layers could be prevented to some extent by increasing blank holder forces. Contrary to forming blanks at high preheat temperatures, fibre fracture happens at room temperature at every blank holder force. An increase in blank holder forces at room temperature results in increasing the FML forming depth before composite failure.