It is well known that adhesion between glass panes and plastic interlayers is a requisite of fundamental importance for the safety and the structural integrity of laminated glass. The level of adhesion depends on many factors: type of materials, autoclave temperature, pressure and time of bonding process, cleaning process etc. Surprisingly, any national or international standard requires minimum adhesion properties in spite of the importance to know and model bonding mechanisms between glass and polymers in order to get high quality LSG and to avoid delamination phenomena between glass and PVB. Furthermore, the high adhesion of PVB to glass ensures, in the post-breakage phase, that fragments remain attached to the plastic film. On the other hand, a Laminated Safety Glass with low PVB adhesion guarantees a higher impact resistance, since more energy is absorbed by elastic deformation of the plastic material. Therefore, the control of the adhesion properties should be such to satisfy at the same time the capacity to absorb impacts and the need for a sufficient bond strength. In Compression Shear Tests (CST) specimens of Laminated Safety Glass (LSG) are inserted in a special test device with an angle of 45° with respect of the loading force so that the compression and the shear components acting in the plane of the plastic interlayer have always the same magnitude. The CST procedure has been performed in order to assess the ultimate shear stresses of PVB interlayers of different kinds. Critical values of shear and normal stresses has been taken as measures of the adhesion properties of PVB to be implemented in calculations to model interfacial adhesion. Different sets of specimens were prepared under different bond process conditions and tested at the Laboratory for Testing Materials and Structures of the University of Pisa. In addition the shear viscoelastic properties, as creep and relaxation, have been investigated on large specimens subjected to different parameter of lamination process. A numerical viscoelastic model of LSG well be adopted to compare the FEM predictions with experimental results.
Adhesion, Creep and Relaxation Properties of PVB in Laminated Safety Glass
FROLI, MAURIZIO;
2011-01-01
Abstract
It is well known that adhesion between glass panes and plastic interlayers is a requisite of fundamental importance for the safety and the structural integrity of laminated glass. The level of adhesion depends on many factors: type of materials, autoclave temperature, pressure and time of bonding process, cleaning process etc. Surprisingly, any national or international standard requires minimum adhesion properties in spite of the importance to know and model bonding mechanisms between glass and polymers in order to get high quality LSG and to avoid delamination phenomena between glass and PVB. Furthermore, the high adhesion of PVB to glass ensures, in the post-breakage phase, that fragments remain attached to the plastic film. On the other hand, a Laminated Safety Glass with low PVB adhesion guarantees a higher impact resistance, since more energy is absorbed by elastic deformation of the plastic material. Therefore, the control of the adhesion properties should be such to satisfy at the same time the capacity to absorb impacts and the need for a sufficient bond strength. In Compression Shear Tests (CST) specimens of Laminated Safety Glass (LSG) are inserted in a special test device with an angle of 45° with respect of the loading force so that the compression and the shear components acting in the plane of the plastic interlayer have always the same magnitude. The CST procedure has been performed in order to assess the ultimate shear stresses of PVB interlayers of different kinds. Critical values of shear and normal stresses has been taken as measures of the adhesion properties of PVB to be implemented in calculations to model interfacial adhesion. Different sets of specimens were prepared under different bond process conditions and tested at the Laboratory for Testing Materials and Structures of the University of Pisa. In addition the shear viscoelastic properties, as creep and relaxation, have been investigated on large specimens subjected to different parameter of lamination process. A numerical viscoelastic model of LSG well be adopted to compare the FEM predictions with experimental results.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
