抄録
It is intended in the present study to investigate direct application of the Griffith fracture criterion to the fracture of viscoelastic materials.
In the experiment, a strip specimen of polybutadiene rubber with artificial flaw of razor cut was stretched up to rupture limit of elasticity under various temperatures and at various strain rates.
The results obtained are as follows;
(1) A simple relation similar to Griffith's criterion was obtained between the fracture strength σba and artificial cut length Ci even in viscoelastic materials, and this relationship depends remarkably upon temperature, that is
σba_??_Ci-α(α=1/2∼1)
(2) The authors attempted to apply Griffith's criterion to the fracture of viscoelastic materials by using modulus Eba at rupture point instead of Young's modulus E.
Hence the fracture energy Γart.c which includes the configuration factor and surface free energy, strongly depends on temperature and strain rate (time).
