Dissipated Energy and Heat Conversion Factor during Low Temperature Fracture in a Notched Glass-Epoxy Composite Material

Abstract

Cracking and debonding of epoxy filler materials generates heat by releasing elastic energy, and the heat output may result in premature quenching of a superconducting magnet because of the low heat capacity of the winding materials of the magnet at low temperatures. This paper considers dissipated energy during the low temperature fracture in a notched glass-epoxy composite material (G-10). The dissipated energy as a function of crack velocity follows from a dynamic strain energy release rate. The dissipated energy is compared with the measured heat output at 77K for partial fractures, and the heat conversion factor, that is the conversion rate of dissipative energy into heat, is obtained. Then, from the average value for the heat conversion factor, the heat outputs at 77K for total fracture and at 4K for partial fracture are predicted and shown graphically.