Effect of blank holder force on strain evolution of forming of steel/SRPP fibre metal laminate

This paper presents findings on forming and wrinkling behaviour of Fibre Metal Laminate system based on steel and self-reinforced polypropylene composite material systems. Stamp forming experiments were conducted at room temperature with a hemispherical punch under different blank holder forces. Resulting surface strains were captured real-time using a 3D photogrammetric measurement system, from which forming limit diagrams could be constructed. Increase in blank holder force resulted in reduced severity of wrinkling and larger formable depth, except at the largest blank holder force for which inter-laminar delamination occurred and lower forming depth was reached. More stretching as opposed to drawing occurred with larger blank holder forces and along axes at 0°/90° to fibre orientations of the composite material