Recently, glass fiber reinforced polymer matrix composite materials have been applied to load-carrying structures due to their high specific strength(S/p)and low material cost. Also, they have been applied to energy absorbing structures such as side door impact beams, bumper beams of passenger cars and guardrails, because they have excellent impact characteristics. Although many researchers have studied the impact characteristics of glass fiber polymer composites, their impact damages and impact energy absorption characteristcs with repect to strain rates have not been thoroughly investigated.
Since the stran rates during the Charpy test or automobile crash accidents are
generally in the range of 10-100 $\sec^{－1}$ and the strength in this range is different from the quasi-static strength, in this study, the tensile and compressive tests of glass fiber epoxy composites were performed to measure the strength variation with respect to strain rates of 1-200 $\sec^{－1}$. The quasi-static tests were conducted using a static material testing machine, and the dynamic tests were conducted using both a dynamic material testing machine with a specially designed gydraulic cylinders and a horizontal-type pneumatic impact tester. For accurate measurements of dynamic characteristics of the composite materials,the stree wave and mass inertia effect of the impact tester were considered. A load cell composed of four strain gauges was devised and calibrated vy the static material testing machine. A birdcage type specimen jig was used to prevent the misalignment between the direction of compressive load and the axis of specimen. In addition, tensile and compressive tests of 50-200 $\sec^{－1}$ strain rates were conducted at a low temperature (－60℃) to investigate the effects of temperature on the strength variation.
From the test results, it was found that the tensile and compressive strengths increased about 100% and 70% at the strain rates of 100-100 $\sec^{－1}$ compared to the quasi static strengths, repectively, while the strengths were little affected by the environmental temperature variation. Also, the impact energy absorption characteristics of glass fiber reinforced composites were estimated using the progressive impact fracture model with the measured stregths, which predicted relatively well the experimental results.
