폴리프로필렌 복합재의 진응력-진변형률 선도 도출

This paper deals with dynamic tensile characteristics for the polypropylene composite used in an IP(lnstrument Panel). This polypropylene composite is adopted in the dash board of a car, especially PAB(Passenger Air Bag) module. The dynamic tensile characteristics are important because the PAB module undergoes high speed deformation during the airbag expansion. The operating temperature of a car varies from -30캜 to 110캜 according to the specification. The dynamic tensile tests are performed at the low temperature(-30캜), room temperature(21캜) and high temperature(85캜). The tensile tests are carried out at strain rates of nine intervals ranged from 0.001/sec to 200/sec. The flow stress increases as the strain rate becomes higher. The flow stress decreases at the high temperature while the strain rate sensitivity increases. Finite element analysis of the tensile test with the special specimen was carried out with unmodified stress-strain curve obtained from the ASTM IV specimen directly. The analysis result shows that the load response is almost same with the experimental result but the strain is rather larger than the experimental result. The stress-strain curves were modified on the basis of the gage length change rate, that is the change of gage length divided by the crosshead stroke. The analysis result with the modified stress-strain curves showed good agreement with the experimental result. The material properties obtained from this research will be useful to estimate the airbag expansion accurately in engineering sense.