Dynamic analysis of CFRC continuous variable curvature cylindrical shells: Theoretical modeling, experimental validation, and mode switching mechanisms

Carbon fiber reinforced composite variable curvature shells (CFRC-VCS) serve as core components of high-performance, multifunctional structures in aerospace and deep-sea exploration. Their complex dynamic characteristics directly affect equipment reliability and are critical for ensuring operational safety. Consequently, CFRC-VCS defined by mathematical functions with spatially continuous variable curvatures are investigated in this paper. The study encompasses dynamic modeling, specimen fabrication, multidimensional validation, and mechanism exploration. First, a semi-analytical dynamic model is established to determine the eigen-characteristics of CFRC-VCS across diverse variable curvature geometries. This model integrates the first-order shear deformation theory (FSDT) with classical laminated plate theory (CLT) by explicitly incorporating spatial initial curvature function modifications and utilizing artificial spring techniques. Second, a two-level validation strategy combining finite element benchmarking and representative experimental testing is employed to assess the validity of the proposed semi-analytical model. Numerical benchmarking was performed using ANSYS software to evaluate continuous shells with diverse curvature profiles, such as parabolic, elliptical, and sinusoidal cylindrical shells. Experimentally, a representative parabolic cylindrical specimen was fabricated using a high precision metal mold and a two stage hot press curing process. An impact hammer modal testing system was subsequently established for experimental validation. Results indicate that the proposed model accurately predicts the eigen-frequencies and mode shapes of the considered CFRC-VCS configurations. Furthermore, it significantly improves computational efficiency compared to ANSYS while maintaining strict accuracy. Finally, the effects of key parameters, such as fiber orientation, focal length, and geometric dimensions, on the eigen-frequency characteristics of the CFRC-VCS are systematically analyzed. Particular attention is given to exploring the phenomenon of mode switching and revealing its underlying mechanisms. The modeling methodology and findings presented in this study provide a robust theoretical foundation for the structural design and vibration suppression of CFRC-VCS.