Characterisation of laminated glass for structural applications

Laminated glass (LG) consists of two or more glass layers bonded by an elasto-polymeric layer, the most commonly used being PVB (Polyvinyl Butyral). LG has improved safety properties compared with single layer glass because the interlayer prevents large sharp pieces from spreading when the glass is broken by impact. Even if one of the layers breaks, the other layer(s) still contribute in carrying the load. Through proper understanding of the interaction between the interlayer and the glass LG could be used in engineering as a load bearing material to a larger extent. This study aims at gaining a deeper knowledge of the behaviour of laminated glass by experimental investigations and by numerical model simulation. To pursue the proposed study, three point bending test with simple support conditions were performed for single layer glass and laminated glass units with three different types of interlayer materials. Corresponding finite element numerical models were created in the software ABAQUS to fit the model with experiment to obtain the bending stiffness and shear stiffness of the interlayer material. The PVB tested showed viscos-elastic material properties, whereas other two interlayer materials, Solutia DG 41 and Sentry Glass, showed linear elastic properties. PVB is the least stiff interlayer material among the three types. Solutia DG 41 and Sentry Glass have similar stiffness, about 13 to 15 times stiffer than the PVB. The behaviour of laminated glass lies in general between the two limits of a layered glass unit with no interaction and a monolithic unit of the same total thickness, depending on the stiffness of the interlayer material. Failure tests of the specimens were also carried out. The obtained strength of glass from four specimens is 80 MPa to 92 MPa with a variation of about 15%. The number of more performed experiments would have better outcome for strength of glass. The bending stiffness of the laminated glass as estimated with the numerical model fitted well with the experimental results with an error of about 2%. Hence the experimentally and numerically obtained results show a good correlation and are thought be possible to use in future larger scale modelling