Rheology of cold-lamination-bending for curved glazing

• Cold lamination bending is a promising technique to obtained free-form curved glazing.
• Glass is cold bent and simultaneously laminated in autoclave; successively it is forced in the desired position.
• After lamination the composite package presents an initial spring back followed by a viscous relaxation.
• A sandwich beam model with viscoelastic core is used to describe the time-dependent response during the various phases.
• A distributed dislocation method is proposed. Comparisons are made with quasi elastic approximation.

A promising technique to obtain free-form curved glazing consists in cold-bending glass panels by forcing them in the desired position. When the glass is laminated, the static state of the forced panel varies in time because of the viscoelasticity of the polymeric interlayer, which causes the decay of the shear-coupling of the constituent glass plies. Here, a model is presented to calculate the evolution of stress and deformation in single-curvature cold-bent laminated glass when, in particular, the glass plies are first cold-bent and, in this condition, are successively laminated in autoclave. With this technique, referred to as cold-lamination-bending, the successive bonding of the plies through the interlayer partially maintains the curvature after that forcing actions are removed. An approximate method based upon a quasi-elastic approach is presented and compared in paradigmatic examples with the full viscoelastic approach.