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

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 mu m 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. [doi:10.2320/matertrans.M2010165]