ลักษณะการสั่นอิสระของแผ่นวัสดุผสมแบบชั้นที่มีรูหลายรูด้วยการวิเคราะห์ไฟไนต์เอลิเมนต์ Free Vibration Characteristics of Layered Composite Plates with Multiple Holes Using Finite Element Analysis

Abstract

This study investigates the free vibration characteristics and estimates the natural frequencies of a Kevlar 49 layered composite plate with symmetric multiple rounded-rectangular holes using finite element modal analysis in ANSYS. The scope covers the first five vibration modes and examines the effects of structural parameters, including boundary condition, number of layers, lamination orientation, fillet ratio, plate length-to-width ratio, cut-out length-to-width ratio, perforation ratio, number of holes in the x- and y-directions, and spacing between holes. The finite element model was developed progressively from a full plate to plates with square, circular, filleted, and multiple cut-outs. Mesh convergence and validation studies were performed before conducting the main parametric analysis. The validation results indicate that sufficiently refined models can reproduce reference results with small errors; for example, the full plate model yielded an error below 0.5%, and the sphere-of-influence or mapped-triangle meshing approaches produced accurate results for curved cut-outs. The parametric results show that fully clamped boundary conditions provide the highest natural frequencies, while increasing the number of layers and using cross-ply or angle-ply laminations increase the natural frequency compared with unidirectional layups. In contrast, increasing the plate length-to-width ratio, cut-out length-to-width ratio, perforation ratio, and number of holes generally reduces the natural frequency. The fillet ratio changes the frequency between the non-filleted square cut-out and circular cut-out limits. These findings provide a useful benchmark for composite plate design and for future experimental or numerical validation.