Long-Term Storage Capability Prediction for Composite Directors in MLRS: Considering the Influence of Actual Environment

To predict the long-term storage capability (LTSC) of composite directors for multiple launch rocket system (MLRS) in the actual environment, a creep constitutive model was established in a three-dimensional nonlinear form, which considered the moisture effect by introducing a moisture shift factor that related to moisture absorption (MA) into the nonlinear Schapery equation. The constitutive model in integral form was transformed into the incremental-iterative form to realize the numerical finite element solution. Quasi-static experiments and short-term creep-recovery tests for E-glass/6509 epoxy resin laminate were performed to obtain the moisture and stress dependent parameters. A coupled numerical model in multi-physical field of moisture diffusion-nonlinear creep was established, and the MA process and creep deformation of composite directors during storage were predicted. The influence law of creep strain on rocket launching was further investigated by establishing the coupled rocket-directors launching dynamics model. The results show that the water diffuses to the inner surface of directors after storage one year in the environment of temperature of 30°C and relative humidity of 70% RH, while a saturated MA state was reached after 8 years storage. Maximum residual strain (RS) in 20 directors locates between the 2nd and 3rd positioning mounting rings, whose distribution likes a saddle-shape. The residual strains of the middle position in the upper and lower rows are the greatest, with a value of 0.38 mm; and the middle position in the left and right columns are the smallest, with a value of 0.33 mm. The creep strain increases the angular displacement and rate in the pitch and yaw directions of the rocket axis.