The sandwich plate can be used to replace the conventional steel stiffened plates on the ship’s hull structure. By using the sandwich plate, not only the stiffness of the plate can be increased but also the overall ship weight can be reduced, as well as the ship payload can be increased. The sandwich plate should be accompanied by the damage identification system to prevent ship structural failure. In this paper, the global damage identification method, which is based on the vibration analysis, is investigated. For that purpose, the vibration-based damage identification using the Finite Element Method (FEM) is explored. The variables being investigated are the damage sizes, damage locations, and the boundary conditions which affect the natural frequencies of the structures. The sandwich plate considered in this study consisted of steel faceplates with the polyurethane elastomer core, which has been checked to meet Lloyd’s register, an international maritime standard. From the analysis, it is found that the fully clamped boundary conditions accompanied by high vibration modes are more sensitive to the presence of artificial damage. The changes in the natural frequencies can be used as a reference to identify the size and location of damage in the sandwich plate.
A lightweight sandwich plate system (SPS) consisted of steel faceplate and polyurethane elastomer composite cores have excellent potential to be applied on the ship structure. Steel faceplate and polyurethane elastomer (PU) cores are frequently applied, but PU has a relatively high material cost. More economical material can be achieved by combining PU with fiberglass as a fiberglass reinforced polyurethane elastomer (FRPU) composite. In this study, the sandwich consisting of steel faceplate and FRPU composite core material is applied in the tanker side hull by investigating the structural performance and weight saving analysis using finite element analysis (FEA). Four sandwich side hull models using different stiffener configurations are compared with the conventional stiffened plate model. The result shows the promising SPS application in terms of structural strength and weight savings. The remarkable stress reduction, deformation, and structural weight reduction due to SPS application are discussed. Therefore, its weight reduction can increase the ship payload so that ship operations will be cost-effective.
The implementation of sandwich panel on the marine structure needs better knowledge of mechanical behaviour, primarily static and dynamic response. The static and dynamic response is investigated due to the application of a sandwich panel on the ferry ro-ro ramp door using finite element software ABAQUS. Five modification models using different sandwich thickness and stiffener configuration are compared using nonlinear static analysis to analyse a comparison of structural strength and weight saving. Additionally, the dynamic response is also investigated due to debonding problem. The influence of debonding ratio, geometry, number of debonding, debonding depth, debonding location, and boundary condition is carried out. Debonding is estimated by using free vibration analysis where Lanczos method for eigenvalues extraction is applied. Result of nonlinear static analysis shows that Model C causes an increase in strength to weight ratio compared to the existing model. Furthermore, natural frequencies are being calculated as modal parameters to investigate the debonding problem. The natural frequency of the debonded model decreases due to discontinuity in the damage area. The dynamic response using natural frequency shift can be performed as structural health monitoring technique on the ramp door model.
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