3点曲げ試験によるCFRTPの縦弾性率および面外せん断弾性率に関する評価

Abstract

Novel CFRTPs (carbon fiber reinforced thermoplastics) for mass production automobile have been developed in Japanese METI-NEDO project (2008-2012 fy). These CFRTPs have not only high mechanical properties, but also high cycle moldability and high recyclability. To perform reliable structural design for the CFRTP, we discussed if the use of conventional test method is applicable or not. Because shear modulus of the matrix of CFRTP is sometimes low, out-of-plane shear modulus of CFRTP would be lower than that of CFRTS (carbon fiber reinforced thermosetting resin), so conventional bending test standard may not be applicable to CFRTP. Hence this paper proposes a simple method to estimate accurate Young’s modulus and out-of-plane shear modulus by three point bending tests with small specimen. Three point bending tests are performed with changing the span length for the same specimen, the results of apparent flexural modulus are plotted, y-intercept and gradient are calculated by least squares method, and Young’s modulus and out-of-plane shear modulus are calculated based on a theory. It was found that Young’s modulus of CF/PP was accurately estimated by the method proposed in this study and underestimated by JIS standard. In addition, out-of-plane shear modulus was also able to be estimated by this method.