Acoustic performance studies on aerogel-filled honeycomb sandwich composites

• Main Author: Zhuo, Kaiyang.
• Other Authors: Sunil Chandrakant Joshi
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Aeronautical engineering::Materials of construction
• Online Access: http://hdl.handle.net/10356/53261
• Institution: Nanyang Technological University

Composite materials are exceptional for their structural properties and are slated to replace aluminium as the main aircraft material. However, composite materials have poor acoustic insulating properties and might bring discomfort to passengers from loud noises such as engine sounds. In order to compensate for this, an aerogel core is introduced to improve the acoustic insulating properties of the structure as a whole. It is thus important to investigate the effectiveness of such a combination of materials. Absorption coefficient and transmission losses are one of the most important parameters studied for acoustic insulation and are the main focuses of this project. Experiments for absorption coefficient are carried out in accordance to ASTM E1050 standards using a standardized impedance tube. These tests were conducted on aerogel filled honeycomb sandwiches, empty honeycomb sandwiches and layered composite samples. BMI and Phenolic GFRP samples were both fabricated to provide a more holistic conclusion. The results of the experiment are optimistic as the insertion of the aerogel core increased the absorption coefficient of the structure particularly at higher frequencies tested. Experiments to estimate transmission losses were conducted using a modified impedance tube setup and a sound level meter. The experiments gave an estimate on transmission loss amplitudes as a relation to their effectiveness as acoustic barriers. The tests were conducted on aerogel filled honeycomb sandwiches, empty honeycomb sandwiches and layered composite samples. The setup is an improvised experiment only able to give estimates of the transmission loss but not absolute numbers. It is useful in comparing between different materials and general trends. The experiment results were optimistic as well with the aerogel filled honeycomb structures performing better than the layered samples. A numerical analysis model was created to simulate the experimental setup for transmission losses using COMSOL Multiphysics. The model allows for cross correlation to the physical experiment to see how it varies with numerical solutions. Overall, the results were quite different from the physical setup experiment and highlights the experiment’s limitation is giving accurate transmission loss figures and can only be used as a general guideline.