Why Windshields Crack at the Edge
83% of replacements per year are caused by edge cracks, with impact points less than three inches from the edge.
Edge cracks are the result of:
1. A weak spot around the perimeter caused from the thermal effect during the manufacturing process.
2. Mechanical stress from the windshield being glued to the vehicle, which also enhances the weak spot.
3. Tension field created by the weak spot, mechanical stress and temperature variance.
4. Fracture mechanics. The critical size and force for fracture decreases as you approach the edge.
5. Theory of Elasticity. Tension stresses are produced in the perimeter from inside vs. outside temperature variations
Survey Results
The statistics below were obtained by combined survey results taken from:1)Replacement shops; 2) repair shops; and 3) mall parking lots. Multiple surveys were completed, totaling over 10,000 vehicles.
The cause of windshield replacements:
1. Edge crack - 83%
2. Sandblasting or pitted - 7%
3. Floater cracks (stone breaks that cracked), impact was past 4 inches from the edge - 5%
4. Vandalism - 2%
5. Stone breaks in acute area (8 1/2" x 11" in front of the driver) - 2%
6. Hail damage, stress cracks and miscellaneous - 1%