A novel low-cost polyurethane (PU) elastomeric material reinforced with mat-form fiberglass for alternative ship material was developed. The hand lay-up technique was used to prepare samples with glass fiber contents of 0, 7, 9, 11, and 15% by weight. Several tests, including density, tensile, and hardness tests, have been conducted to investigate the effect of fiber content on the material properties of the developed materials. The test results found that only composites with 0% (PU) and 7% (PFg-7) fiberglass had met all Lloyd’s Register criteria. PFg-7 has a density of 1,098 kg/m ³ , a hardness of 66.15 shore-D, a tensile strength of 21.32 MPa, and an elongation at break of 47.06%, a higher hardness, elastic modulus, and yield strength than PU. PFg-15 achieved the highest density, hardness, tensile strength, elastic modulus, and yield strength, which were 1,228 kg/m ³ , 68.85 shore-D, 32.13, 2,176, and 30.89 MPa, respectively. The elastic modulus and yield strength of PFg-15 were 5.6 times and 3 times higher than those of PU but PFg-15 did not meet the elongation at break criteria. PFg-9, PFg-11, and PFg-15 showed brittle properties, as indicated by relatively high hardness, elastic modulus, and yield strength compared to the results from various references.

As one of the most dangerous defects in the sandwich panel, debonding could significantly degrade load carrying capacity and affect dynamic behaviour. The present work dealt with debonding detection of the rectangular clamped hybrid sandwich plate by using ABAQUS software. The influence of various damage ratios on the linear and nonlinear dynamic responses has been studied. The finite element model was initially validated by comparing the modal response with the experimental test. Rectangular debonding was detected by comparing dynamic responses of free and forced vibrations between intact and debonded models. A wide range of driving frequency excitation corresponding to transient and harmonic concentrated loads was implemented to highlight nonlinear behaviour in the intermittent contact in the debonded models. The results showed that debonding existence contributed to the natural frequency reduction and modes shape change. The numerical results revealed that debonding affected both the steady-state and impulse responses of the debonded models. Using the obtained responses, it was detected that the contact in the debonded region altered the dynamic global response of the debonded models. The finding provided the potential debonding diagnostic in ship structure using vibration-based structural health monitoring.

Rizky Chandra Ariesta, Achmad Zubaydi, Abdi Ismail, Tuswan Tuswan; Original scientific paper, pp. 1-8 Download

Ship materials are required to have good strength but with the lightest mass possible. The faceplate layer is made of a material with high strength and stiffness, while the core layer is made of a material with lower strength, stiffness, and density. In this study, a PU composite was applied to ship sandwich plates. Strength analysis was carried out to determine the feasibility of applying the sandwich plate to the oil tanker deck using the Finite Element Method. Sandwich plate deck has a stress value of 139.73 MPa. When compared with conventional models, the difference in stress reaches 80.26 MPa or about 36.48% of conventional models. The highest stress on the sandwich model meets the permitted stress. This study proves that the sandwich plate system (SPS) could reduce stress in the tanker deck structure. Steel faceplate and polyurethane elastomer composite cores have outstanding potential to be applied as sandwich plate systems on ship decks.

Development of lightweight core sandwich based bioresin for ship structure application needs more attention. Bioresin from vegetable oils constitutes single, easily available, low cost, and biodegradable materials. In this research, the vinyl ester bioresin based Vinyl Ester-Coconut Oil (VE-CO) and Vinyl Esters-Soybean Oil (VE-SbO) containing 4 wt% vegetable oils are developed. The influence of vegetable oil addition in bioresin is characterized by visual observation and physical testing, including FTIR, density, hardness, and tensile test based on Lloyds Register standard. Visual testing shows that VE without vegetable oil is more transparent compared with VE with vegetable oil. The density test shows that adding vegetable oil decrease the apparent density. Vibration pattern indicates the presence of O-H, C-H, C=O, C=C, and C-O-C, which demonstrate the ability to bind, which leads to the potential formation of a polymer blend and elongation increase. Moreover, hardness decreases due to the absence of chemical bonds that occur between vinyl esters and vegetable oils. The addition of vegetable oil to vinyl ester bioresin reduces tensile strength and increases the elongation at break. So, density and tensile strength criteria meet Lloyd’s Register Standard while the other criteria are not fulfilled.

Ship material technology needs lightweight and strong enough material, where one of the solutions is a sandwich plate. Steel faceplate and room temperature cured polyurethane elastomer (RTC-PU) cores are frequently used configurations on ship sandwich plates. But RTC-PU has a relatively high cost. Polyurethane elastomer casting has a lower cost and easy-to-obtain. More economical core materials can be achieved by combining casting polyurethane elastomer with fiberglass, so fiberglass-reinforced polyurethane elastomer (FRPU) composite is obtained. In this study, FRPU is used as a core for ship sandwich plates. Strength and weight assessment of conventional and side-shell sandwich plates were performed to determine the benefits of applying the sandwich plate to side-shell tankers using the Finite Element Method. The application of the sandwich plate results in a stress reduction of 27.02% and a weight reduction of 4.2% compared to conventional side-shell structure. The highest stress of the side-shell sandwich plate is below the steel yield stress so that the sandwich plate is acceptable for the side-shell structure. The implementation of sandwich plates can reduce the weight of ship structure so that the ship’s payload can be increased and its operation will be more efficient.