Transient moisture concentration profiles and hygroscopic stress fields in an asbestos phenolic nozzle liner

摘要

Surface cracks in an asbestos/phenolic liner for a rocket engine nozzle led to an investigation of the possible causes for the cracks. An analytic technique was devised wherein stresses due to moisture gradients were calculated via an analogy to thermal stresses. Experimental data were generated on moisture absorption rates and dimensional changes due to changes in the amount of moisture absorbed. The experimental data were used in the finite element computer program ANSYS with moisture concentration gradients substituted for temperature gradients and a coefficient of moisture expansion substituted for the coefficient of thermal expansion. The results showed that uncontrolled moisture abosorption/desorption can result in stresses higher than the material strength.