Measuring Failure Stress of RTM6 Epoxy Resin under Purely Hydrostatic Tensile Stress using Constrained Tube Method

The temperature dependence of the failure stress of RTM6 resin under nearly pure hydrostatic tension was measured for two standard curing cycles. The stress in the resin was achieved by confining the resin in capped quartz tubes while cooling from the curing temperature. The stress was estimated from the deflection of the outer wall of the quartz tube relative to its unstressed diameter assuming linear elasticity. The failure stress increased monotonically on cooling from the curing temperature and reached a maximum value of 28 MPa at 108 °C. This value is roughly consistent with the failure stress estimated from a void initiation failure criterion using room temperature tensile strength.