切欠きをもつGF/PP板の高速引張試験による破壊

Abstract

The effects of notch geometry on the tensile strength of notched fiber-reinforced polymer (FRP) plates in dynamic tensile strength tests were investigated. A short-glass-fiber-reinforced polypropylene (GF/PP) plate containing 30% E-glass fiber by weight was prepared by injection molding. The notch-root radii were 0.5, 1, and 2mm, while the notch depth ranged from 2 to 5mm. Dynamic tensile strength tests were carried out at room temperature of 23°C and a tensile speed of 1000mm/s. The validity of the fracture criterion based on the concept of the severity near the notch root was previously confirmed for notched FRP plates under static loading. In other words, the maximum elastic stress at fracture is determined only by the notch-root radius. This is accomplished by the experimental data of the static tensile test at a constant cross-head speed of 0.5mm/min (= 0.008mm/s). When the time to a fracture was the same, the results of the dynamic tensile strength tests showed that the maximum elastic stress at fracture is determined by the notch-root radius but is independent of the notch depth. Thus, the concept of the severity near the notch root could be applicable to the fracture of notched FRP plates in dynamic tensile tests. On the other hand, the fracture strength of FRP is time-dependent, and this dependence is called viscoelastic behavior. Therefore, when the tensile speed is varied, the maximum elastic stress at fracture would be determined by the notch-root radius and time.