Advantages And Disadvantages Of Laminated Glass

Laminated Glass (LG) comprises two layers of glass and a layer of viscous elastic polymer Polyvinyl Butyral (PVB) film. Two layers of glass and PVB in between are put together under heat and pressure to make LG. Interlayer improves mechanical properties such as impact resistance, tensile strength and fracture toughness of the laminated glass. It also increases the area of impact which increases the impact resistance as a result. Interlayer in between keeps together broken pieces that can possibly cause dangerous incidents or accidents. The LG as a system dampens the energy of impact improving the brittle structure when compared with monolithic glass structure. LG is mainly used in automotive industry and structural applications. LG act as a

A finite element solution is determined for such a layered system assuming that the effect of the PVB will be low. Numerical solution was provided for the structure having two adjacent plates without any interaction. It was found at lower temperatures glass behaves as monolithic glass whereas at high temperature it behaves as layered glass. Vallabhan [3] [1987] has stated strength factors for different load and aspect ratio conditions. Variation of the strength factor is observed for different forces applied over glass plates, Involving nonlinear theory of rectangular plates.
Strength factor (SF) is given as:
Strength factor = Maximum principal tensile stress in monolithic glass plate Maximum principal tensile stress in layered glass

It was observed that a severe degradation of effective shear modulus undergoes in the interlayer at and above 77° C whereas LGbehave like monolithic glass at temperatures up to 49° C, after which degradation in shear modulus of the interlayer occurs and the glass begins to behave in the manner of a layered glass system, and the LGbehaves like monolithic glass when subjected to even long term loading at and below 0° C. it was also found that hard interlayer displays no creep at 1.4° C, while the soft interlayer displays considerable creep, But this fact reflects that the results from the experiments of Behr which yield a type factor of 1.0 for up to 49° C, may be true only for the specific PVB used in these experiments unless strength factor (SF) is greater than 1.0, phenomenon is valid for the concerned geometry and loading. So, SF should be applied with reference to transition temperature of the specific PVB used in LG. Vallabhan [1993] derived a mathematical model for analyzing the bending behavior of LGunits in which the total potential energy of plates was minimized using variational methods. They assumed that the plates possess both bending and membrane strain energies and interlayer has only shear strain energy. Von Karman nonlinear theory of the plates was used for modeling of the glass plates. The total potential energy of the system with respect to