Evolution of meridian strains in stamp forming of steel-based fibre metal laminate

In light of recent climate changes, tight regulations have been imposed on automotive manufacturers to reduce carbon dioxide emissions of new vehicles produced. As result, making light-weight vehicles has been many manufacturers' primary interest. To help achieve such goals, researches have been carried out on using Fibre Metal Laminate (FML) structures based on thermoplastic fibre-reinforced composites for making automotive panels. This paper presents findings on stamp forming characteristics of an FML based on steel and self-reinforced polypropylene under different blank holder forces (BHFs) at room temperature. A custom-built 30-ton stamping press with a hemispherical punch and an open die was used to perform the experiments and a 3D photogrammetric strain measurement system (ARAMIS) was used for capturing resulting surface strains real-time. FMLs were observed to fail by wrinkling at varying depths depending on the BHF, with wrinkling becoming more prominent at lower BHFs and inter-ply delamination occurring at higher BHFs. Studying evolution of meridian surface strains along and off-axis to fibre directions provided understanding of the manner in which different regions undergo varying modes of deformation throughout the forming process. Larger strains were observed at regions close to flange area of an FML sample along 45° meridians than in fibre directions.