A Nonlinear Viscoelastic Model for Describing the Deformation Behavior of Braided Fiber Seals

Abstract

A nonlinear viscoelastic model has been proposed to describe the time-dependent deformation behavior of a fiber assembly including braided fiber seals. The model is based on the standard solid model, but modified to contain three nonlinear spring and damper elements. For a fiber assembly under a compressive load, the deformation status can be characterized by the fiber volume fraction V_f. The elastic spring and viscous damper elements in the proposed model are assumed to be nonlinear functions of V_f. General deformation solutions in the cases of creep and stress relaxation are obtained, as are nonlinear functional forms of the spring and damper elements versus V _f through a series of stress relaxation experiments on the fiber seals. The results are then used to analyze the deformation behavior of the fiber seals in the case of creep, and in other cases with ramp pressure or ramp displacement conditions.