Stress Analysis of Metallic Pocket-Motor Cases Reinforced with a Viscoelastic Fibre Overwind

Analytical stress solutions are presented for a metallic rocket motor case reinforced with a prestrained fibre overwind, with viscoelastic properties, under both constant and varying temperature histories. The treatment is in terms of the "reduced time " proposed by Schwarzl and Staverman, with the Williams/Landel/Ferry form of the "shift function". The analysis is reduced to the solution of a Volterra integral equation. For a constant temperature history and using the "standard linear solid" representation of the material properties of the overwind, this equation can be solved in closed form. For varying temperature histories the equation is solved using a finite-difference techniaue proposed by Lee and Roger and improved by Margetson. T1;e effects of fibre relaxation on the internal pressure reouired for the initiation of yield in the rotor case are evaluated and discussed for a number of temperature historie