Energy dissipation and temperature rise associated with crack extension in a woven glass-epoxy laminate at low temperatures

Failures, fracture (cracking) and debonding of filler materials used in the winding of a high-performance superconducting magnet generate heat. When combined with the high thermal response of the materials at low temperatures, the small heat input may result in premature quenching of the magnet. An analytical procedure, using a finite element method, was developed to calculate the dissipative energy and temperature rise associated with crack extension in a woven glass-epoxy laminate(G-10) at low temperatures. The amount of energy dissipated during partial fracture of the test specimen is calculated as a function of crack speed using a dynamic strain energy release rate. The dissipative energy is compared with the heat output determined experimentally at 77 K, and the conversion rate of dissipative energy into heat is obtained. From the average value for the conversion rate, the heat outputs at 77 K for total fracture and at 4 K for partial fracture are predicted. Temperature elevations at the crack tip are also calculated.