Effect of Glazing System Parameters on Glazing System Contribution to a Lightweight Vehicle's Torsional Stiffness and Weight 2000-01-2719

A finite element model of a lightweight vehicle body-in-white has been developed to study the contribution of a lightweight vehicle's glazing system to its overall structural rigidity. This paper examines the effect of the glazing thickness and glazing molding stiffness on the glazing system contribution to a lightweight vehicle's torsional rigidity. The individual stiffness contributions of the front and back glazing were determined, as well as the weight of the glazing as a function of its thickness.

In the first set of analyses detailed in this paper, the torsional and bending loadcase was investigated by comparing the baseline model to a no-glass model. It was shown that the glazing system contributes significantly to the overall structural rigidity of the auto-body. The difference was mainly in the torsional rigidity which was 12.4% more rigid than the no-glass model. The bending rigidity was only increased by 0.5% in the glazing model. Since this was the case, further investigation on the torsional rigidity was necessary.

The next step was conducted using the lightweight vehicle model to determine the effect of the glazing thickness and glazing molding stiffness on the glazing system contribution to the lightweight vehicle's torsional rigidity. Only torsional loading is considered here because in the previous analyses it was determined that the glazing system did not significantly contribute to the car's bending stiffness. First, analyses were conducted in which the glazing thickness and molding stiffness were independently varied by application of a scale factor to the baseline values. For each analysis, the car's torsional stiffness was calculated. A curve fit was performed on the results to yield a relation for the torsional stiffness as a function of both the glazing thickness and the glazing molding stiffness. In order to test this relation, further analyses were conducted in which the glazing thickness and glazing molding stiffness were varied concurrently by the same amount. The results of these analyses served to validate the curve fit. Both the curve fit and the data show that the glazing thickness can be significantly increased or reduced with only a minimal change in torsional stiffness contribution. The results also show a marginal gain in torsional stiffness contribution from increasing the glazing molding stiffness and a significant loss in torsional stiffness contribution from decreasing the glazing molding stiffness.

Two analyses were conducted to determine the individual contributions of the front and back glazing to the car's torsional stiffness. These analyses used the baseline values of the glazing thickness and molding stiffness. In each analysis, either the front or back glazing was removed from the car and the resulting torsional stiffness was calculated. The results of these analyses show that the front glazing provides 10.2% of the glazing system's contribution to the car's torsional stiffness and the back glazing provides 2.2%.

Finally, the weight of the glazing as a function of the front and back glazing thicknesses was calculated. It was determined that the glazing weight is linearly proportional to its thickness. With the baseline values for front and back glazing thickness, the total glazing mass is 22.27 kg. The masses of the front and back glazing make up 62% and 38% of this figure, respectively.