Resistance of Structural Silicones to Creep Rupture and Fatigue

Structural silicone sealants are subjected to repeated wind and thermal load cycles and, in certain applications, to sustained loads. Data from two types of creep tests are presented, one using constant loading and the other ramp loading. Both were done on an acetoxy silicone. Fatigue data are reported for tension on a neutral cure sealant, tension on a two-part silicone in insulating glass joints, and shear on an acetoxy silicone. All fatigue testing used full reversal, constant load amplitude cycling. Regression analyses on failure stress versus time or cycles to failure and on stress versus the logarithm of time or cycles to failure are discussed in relation to current design practice. Some of the problems associated with creep and fatigue testing of silicone sealants are explained.