Impact Fracture Behavior and Fracture Criterion of Brittle Beams, plates and Circular Rings

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Square plates of laminated safety glass, of which interlayer is the polyvinyl butyral, are impacted transversely by dropping a circular steel punch and perforated. the corresponding fracture behaviors are photographed by a camera connected with the stroboscope. The penetration fracture of the laminated safety glasses consists of the following three steps;The first step is the brittle fracture of the opposite outerlayer glass to impact side, the second step is the brittle fracture of the outerlayer of the polyvinly butyral. The limits of the impact energies U_1 and U_2, which are the energy to initiate crack in the outerlayer glass and the penteration energy of punch, are measured by changing the dropping height of punch. U_1 increases proportionally to the thickness of outerlayer glass. U_p incrases proportionally to the thickness of interlayer. The strongest relation was observed between U_p and the crack propagation phenomena in outerlayer glasses. Considering the relations mentioned above and material properties of plate, the formula estimating U_p is proposed.