Effects of Electron Beam Irradiation on Impact Value of Novolak-Type Phenol CFRTP

Abstract

Homogeneous low voltage electron beam irradiation (HLEBI) improved the Charpy impact value (a uc ) of carbon fiber reinforced thermoplastic novolak-type phenol polymers (CFRTP) composite sheets with 2 mm thickness, although the irradiated depth estimated was 182.5 ± 33.5 μm on both side surfaces. The a uc values at low fracture probability (P f ) of 0.06 for CFRTP irradiated at 0.30 MGy (kJg ―1 ) was 60 kJm ―2 , which was 32% higher (46 kJm ―2 ) than for CFRTP before irradiation. Although the lowest impact values (a s ) estimated by three-parameter Weibull equation was zero for CFRTP before irradiation, HLEBI enhanced the a s value. The highest a s value was more than 59 kJm ―2 for CFRTP irradiated at 0.30 MGy. Thus, HLEBI remarkably enhanced the a s value, as well as the a uc value at low P f value. Since HLEBI enhanced the Weibull coefficient (n), it also enhanced the reproducibility of CFRTP samples. The maximum n value was found at 0.22 MGy HLEBI dose. The interfacial friction force, as well as the strengthening of both carbon fiber and novolak-type phenol resin probably contributed to the HLEBI effects to enhance the a s value of CFRTP, as well as enhancement of reproducibility.