Abstract: In order to investigate the moisture absorption-creep coupling behavior during long-term stacking storage of box-type composite directors for multiple launch rocket systems, a three-dimensional orthotropic nonlinear creep constitutive model considering moisture effect is derived by introducing the moisture shift factor into the Schapery's nonlinear equation. The E-fiberglass/6509 epoxy resin composite laminates were prepared, and the moisture absorption test, static mechanical performance test and short-term creep-recovery test were carried out to obtain the hygroscopic parameters and the moisture- and stress-dependent nonlinear creep parameters. Finite element method was used to establish a numerical model of coupled moisture diffusion-nonlinear creep analysis. The creep deformation of composite directors after 15 years of storage was predicted. The calculated results show that the moisture diffuses to the inner surface of director after one year of storage in the general military warehouse and reaches the quasi-equilibrium uptake state after eight years. The maximum residual deformations of all 20 directors take place between the second and third positioning rings, and are approximately distributed in a saddle shape in three-dimensional space. The residual deformations of the directors between upper and lower rows are the largest with a maximum value of 0.38 mm, while those of the directors between left and right columns are the smallest with a minimum value of 0.33 mm.

Key words: multiplelaunchrocketsystem, compositedirector, stackingstorage, nonlinearviscoelasticity, moistureabsorption-creepcoupling