Impact penetration energy of laminated glass and its penetration formula.

Square plates of laminated glass, whose interlayer is the polyvinyl butyral, are impacted transversely by a circular steel ball. The impact penetration energy Up, which is the penetration energy of the ball, is measured by changing the dropping height of the ball. The penetration fracture of the laminated glasses consists of three steps. The first step of fracture is until initial cracks initiate in the outerlayer glasses, the second fracture is the bending fracture of the laminated glass and the third is the fracture due to shearing the interlayer. Considering the relations mentioned above and material properties of laminated glasses, we proposed the formula for estimating Up. The validity of this formula was discussed in terms of the results of experimental and theoretical examinations.