低温におけるガラス繊維強化有機複合材料の破壊じん性に関する研究

概要

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The paper is concerned with the fracture toughness of glass fiber reinforced plastics at low temperature. By the use of compact tension specimens of a random chopped-strand SMC composite, fracture toughness tests were performed at temperatures, 298K, 200K, 77K and 4K. The main results are summarized as follows : (1) At the lower temperatures, the nonlinearity of load-crack mouth displacement curve becomes remarkable and the acoustic emission activity becomes higher. (2) From the microscopic observation, it was found that the zone of damage consisting of fiber debonding, matrix cracking and fiber breakage is formed in the vicinity of the notch tip. (3) The fracture toughness value K_<AE>, obtained as the stress intensity factor which corresponds to the onset of abrupt increase of the accumulated acoustic emission energy, is larger, as the temperature is lower. (4) At a low temperature, the fracture toughness value K_Q obtained by the 5% offset procedure of ASTM E 399 is extremely smaller than the fracture toughness value K_<AE> at the same temperature. Thus, the value K_Q could be inappropriate for the fracture toughness at a low temperature. (5) The equation involving the tensile strength of fibers is derived for the fracture toughness of the random chopped-strand SMC composite at a low temperature.
一般社団法人日本機械学会の論文
1987-07-25