Advanced CAE Windscreen Model

CAE model's head impact fracture prediction.

HORIBA MIRA delivers the most advanced Computer Aided Engineering (CAE) windscreen model that cuts cost, reduces development time and provides an accurate solution to virtual safety development.

ADAM OPEL AG wanted to develop pedestrian safety measures earlier in their vehicle development cycle rather than relying on expensive and time-consuming hardware testing.

Normally such safety measures would be developed utilising Computer Aided Engineering (CAE). However, because the then existing CAE technology consisted of complex material behaviour, which includes fracture, it was unable to realistically simulate windscreen impacts.

Our CAE engineers set to work on developing advanced material models of each component of the windscreen, namely the glass, the fixing adhesive and the Poly Vinyl Butyral (PVB) foil, which is a resin that bonds the glass providing strength and impact resistance. The properties for both the PVB and the fixing adhesive were obtained from a number of tensile tests and corresponding CAE models were built and correlated. The development of the windscreen glass model required a very novel approach to be taken.

Fractured windscreen post head impact testing.

The engineering team needed various and very accurate performance characteristics of the windscreen glass at different locations in order to understand and quantify how the glass properties were affected by how it was loaded, its shape and its manufacturing process. Using a specifically designed test rig, the glass was mounted and covered in a photo-elastic coating. Then with a polarised light source along with other instrumentation, the glass characteristics were measured and recorded for each mm of deflection during various loading conditions.

The results of the testing, combined with head impact data from both drop testing and full scale testing were combined to produce the most advanced windscreen simulation model available. The CAE model accurately replicates both radial and tangential crack propagation which is critical to the windscreen’s stiffness. It also accurately predicts pedestrian head impact injury levels, thereby now allowing for the virtual development of protection measures.