Abstract:

This paper aims to develop a theoretical model for thin cylindrical shells made of composite materials with thermal expansion and hygroscopic expansion coefficients. The analytical expression of strain energy under complex environmental conditions is derived. Based on the principle of minimum potential energy, the effects of environmental parameters on the strain energy, twist curvature, and secondary stable principal curvature of T700/Epoxy, T300/5028 Graphite-Epoxy, and AS7/M21 carbon fiber/epoxy resin-based composite cylindrical shells are studied. A finite element model of the cylindrical shell structure is established to numerically simulate the bistable deformation process of the shell, and the numerical results are compared with the theoretical results. The results show that the twist curvature of T700/Epoxy and AS7/M21 is relatively stable within the temperature range of 20°C to 120°C and humidity range of 0% to 1%, with maximum strain energy reductions of 32.7% and 9.1% respectively. The strain energy increment of T300/5028 Graphite-Epoxy cylindrical shells is as high as 914.6%, indicating that high temperature and high humidity have a significant impact on the bistable performance of the structure. Through quantitative analysis of the mechanical properties of composite materials under different temperature and humidity conditions, this study provides a scientific basis for the selection of materials and optimization of the application environment for bistable structures, contributing to the improvement of structural design reliability and durability.

Key words: bistable state, composite material, cylindrical shell, complex environment, curvature