Vibration analysis of anisogrid composite lattice sandwich truncated conical shells: Theoretical and experimental approaches

Abstract

Drawing upon both theoretical and experimental methodologies, this study investigates the vibrational characteristics of lattice sandwich truncated conical shells featuring composite ribs made of carbon and E-glass fibers. Toward this aim, the equations of motion along with the corresponding boundary conditions of such sandwich shells are derived using classical Donnell’s shell theory and the smeared stiffness technique. Subsequently, the governing equations are solved to obtain a closed-form expression for natural frequencies employing the Galerkin method. In addition, ABAQUS simulations are presented to study the vibration behavior of single-skin and three-skin conical shells. To validate the theoretical methods, the specimens of three-layer sandwich conical shells were fabricated from two Kevlar fabric laminates and a composite lattice core with hexagonal cells using a manual filament winding process. The composite ribs consist of carbon and E-glass fibers with a ratio of 3:1. Finally, experimental modal tests were conducted to extract natural frequencies and mode shapes by measuring frequency responses at 40 points over a duration of 60 s using a laser vibrometer. A strong correspondence is observed between the theoretical outcomes (utilizing the Galerkin and FE methods) and the experimental findings (with a maximum discrepancy of approximately 16% for the initial four mode shapes). Findings indicate that the excellent performance of the composite lattice core in vibration behavior, which can increase approximately 19% and 16% the natural frequencies corresponding to the first and second mode shapes, respectively.