抄録
This paper presents the dynamic stress-strain properties of styrofoams. Two ballistic pendulums were used in this experiment. The specimens, which had been bonded on the end surface of the pendulum being impacted, were loaded by the impact pendulum. The acceleration-time curves induced in the impacted pendulum were measured. The dynamic stress and strain were calculated by integrating these acceleration-time curves numerically. The effects of the strain rates and the number of impact loadings on the dynamic properties of styrofoams were examined and the accuracy of the test result was also discussed. The results obtained are as follows:
(1) The dynamic stress-strain properties of foamed plastics can be obtained with the accuracy of about 3 percent by this experimental method.
(2) The strength and stiffness of styrofoams increase with increasing the strain rate up to about 20/sec, beyond which they start to decrease.
(3) The stiffness of styrofoams is remarkably reduced by the first application of impact loading but does not change any more by its further successive applications.
(4) At the strain rate of about 35∼40/sec, styrofoams disintegrate in an explosive manner. Therefore, the styrofoams seem to have the critical deformation rate in the vicinity of this strain rate.
