Stationary glass, especially the windshield, is part of the vehicle structure. It contributes to the strength of the roof and pillars, and helps keep occupants from exiting the vehicle during a collision. Completely shattered glass or cracks where the glass was struck are examples of easily identifiable glass damage. However, the overall structural integrity of a stationary glass assembly may be adversely affected when exposed to excessive heat from a vehicle fire. This type of damage may not be recognized as easily.

Figure 1. Fire damage to this vehicle was caused by faulty wiring in the dash panel.

Figure 2. The plastic trim panel at the bottom of the windshield started to warp from excessive heat, caused by a vehicle fire.

Figure 3. The sample shows substantial degradation of the urethane adhesive.

    Although some vehicle fires are caused by collisions, many are not. Other causes for vehicle fires include faulty wiring (see Figure 1), fluid leaks, the exhaust system, smoking, and vandalism. A vehicle may also be exposed to excessive heat or fire if it is parked near a burning building or another vehicle. A vehicle that has been damaged by fire requires a close inspection of stationary glass, even if there are no obvious signs of damage. Heat-
damaged parts, adjacent to stationary glass, may indicate that the glass should be inspected further (see Figure 2).

Glass inspection
Inspecting stationary glass on a fire-damaged vehicle may include checking for a smoky haze or stain that cannot be removed using conventional glass cleaners and techniques. Permanently stained glass should be replaced because the reduced visibility is a safety hazard.
    Also look for signs of delamination on laminated glass. Delamination is when one or both layers of glass begin to separate from the inner polymer layer. This may appear as a bubbling near the edge of the glass. Glass that appears to be delaminating should be replaced because the structural integrity of the glass is likely to have been compromised.

Adhesive concern
The integrity of the adhesive that bonds the glass to the vehicle is just as important as the glass itself. It is a reasonable concern that the structural integrity of the urethane adhesive may also be adversely affected when exposed to excessive heat, and result in a much weaker bond.
    To confirm this, I-CAR conducted some basic tests to see how heat may affect glass urethane adhesive. The materials we used for the test included 63 mm (2 1/2") long coupons cut from an OEM painted panel, glass urethane, and square-shaped steel tubing. Steel tubing was initially chosen because we intended to use tensile-testing equipment to determine the extent the adhesive was weakened. However, we realized that this would not be necessary after some preliminary experiments.