Bending behaviours of laminated glass and an experiment based method to determine the effective thickness

This study investigates the bending deformation behaviour of laminated glass (LG) and develops an experimental methodology for determining effective thickness applicable to composite glass with diverse configurations. The research reveals that the mechanical properties of LGs are significantly influenced by the shear transfer efficiency of polyvinyl butyral (PVB) interlayers, which is primarily governed by thickness. LGs with thin PVB interlayers (0.38 mm) demonstrate enhanced flexural rigidity, and peak load is approximately ~ 15.2% greater than the LGs with the same thickness of glass but thicker interlayers (1.52 mm), exhibiting near-monolithic behaviour. Through digital image correlation (DIC), the interlayer slip of different specimens is analysed through identification of localised shear bands in the interlayer region. Furthermore, the transverse strain contours reveal that LGs consistently develop dual neutral axes during bending, regardless of glass and interlayer thickness variations, highlighting inherent limitations in PVB shear transfer capacity. DIC also characterises the fracture modes of LGs. Experimental bending strength of LGs derived through Hook’s law and fracture strain data indicate that LGs with thin interlayers exhibit around 21.3% higher strength than that of thick ones. Finally, the effective thickness of PVB LGs, vacuum glazing and multi-laminated glass determined by the experimental methodology is confirmed the reliability through bending stress comparisons between calculated and experimental values. These results demonstrate the superior applicability of the proposed method for complex-structured composite glass compared to conventional approaches.