Effect of aspect ratio variations on forming limit diagram of glass-fibre reinforced polypropylene composite at room temperature

This study investigates the formability of pre-consolidated glass-fibre reinforced polypropylene composite during stretch forming conditions. Fixed boundary condition was applied to the sheets through a lock-ring and samples were deformed up to the depth of failure in an open-die custom-built press by a hemispherical punch. Specimens with different aspect ratios were employed to induce different deformation modes. Deformations and their evolutions were captured and recorded by an in-situ 3D photogrammetric measurement system (ARAMIS). Resultant major and minor strains were calculated and plotted in 2D strain space to construct a Forming Limit Diagram (FLD) which elucidates safe and failed deformation margins during stamp forming procedure. It was found out that Woven glass-fibre reinforced all-polypropylene composite sheets do not tend to exhibit thinning or localized necking behaviour during forming and hence their Forming Limit Diagrams would not contain marginal regions as in sheet metals.