Cryogenic shear fracture tests of interlaminar organic insulation for a forced-flow superconducting coil

Since a forced-flow superconducting coil consists of metallic conductors and organic insulation with relatively low mechanical strength, a knowledge of mechanical behavior and properties of the interlaminar insulation is of great importance. Shear fracture tests of interlaminar organic insulation under biaxial stresses were carried out at low temperature, by using test specimens made of stainless steel pieces bonded with impregnated organic insulation (glass-kapton-glass). Inclination of adhesive surface was varied to get combinations of the debonding stresses and to construct the critical curve of the debonding fracture. The test results show that the critical curve approximately agreed with the Mohr-Coulomb criterion and that shear fracture resistance of the bonding interface enhanced with the increase of compressive stress value