The Physics of a Windshield Impact

Nearly every driver and commuter has had the unpleasant experience of a cracked windshield resulting from debris impacting the glass. That sudden, loud and unmistakable sound of a rock striking glass can ruin your day and cost you money, especially if the damage is left to expand into even larger cracks.

As random as windshield damage can be, researchers from Aix-Marseille University in Marseille, France have discovered some interesting data about this topic; some in the industry would say ‘interesting’ is an understatement. These researchers recently published research that points to a possibly revolutionary connection between an object’s velocity and the number of radial cracks that result from the object impacting glass. Nicolas Vandenberghe and his fellow colleagues discovered that the number of cracks is proportional to the square root of the impact speed for small steel projectiles hitting samples of plexiglass.

As an example, quadrupling the speed of a small rock would double the number of triangular cracks emanating from the impact site. While this knowledge is meaningless to all the drivers out there right now dealing with windshield damage, this research may prove extremely useful in ballistics testing, forensics, and even protecting spacecraft from the dangers of the cosmos.

 

 

Video credit: N. Vandenberghe; Aix-Marseille University

 

The researchers at Aix-Marseille University recorded small metal objects striking sheets of plexiglass with high-speed cameras. The velocity of the metal objects was varied, as well as the thickness of the plexiglass throughout the experiment (two impacts from these tests can be seen above).

Automotive glass has undergone numerous changes over the years, and this research may bring us closer to the possibility of windshields more resistant to this type of damage while being affordable enough to equip on the average vehicle. Aside from automotive glass, this could have even wider implications in areas such as crime scene investigations (tracking object velocity through glass) and aerospace.

 

Original article at Physicscentral.com

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