Hygrothermal effect on behaviours of composite materials

• Main Author: Tan, Andy Wei Ming
• Other Authors: Seah Leong Keey
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Materials::Composite materials
• Online Access: http://hdl.handle.net/10356/75899
• Institution: Nanyang Technological University

The use of Fibre-Reinforced Polymer gained popularity mainly due to its high strength to weight ratio. In the aviation and maritime industry, the composite material used have structural strength that are comparable to metallic alloys but at a lighter weight. In this project, the hygrothermal effects on composite materials containing woven glass fibers embedded onto Bismaleimide (BMI) resins are investigated. In addition, the author will analyse the water absorption behaviour of the composite specimens that were exposed to 3 different environmental conditions, namely -5oc cold water bath, 23oc room temperature water, and 85oc hot water bath. The exact absorption curves were also determined based on data collected from the 3 conditions. In addition, three different diffusion models will be used to model the absorption curve of the composites: Fickian, Langmuir and Jacobs-Jones. After which the author will evaluate and determine the best model to represent the water diffusion under each different condition for this project. At the conclusion of this study, it was confirmed that the water diffusion rate is greater under high temperature conditions and the specimens achieved saturation/equilibrium in a shorter amount of time. The absorption processes for all specimens were found to be Non-Fickian. Langmuir and Jacobs-Jones models were able to predict the absorption curve with higher accuracy in comparison to the classical Fickian Model. Next, 2 specimens were taken out at 2-month intervals from each condition to undergo tensile testing in order to investigate the change in mechanical properties ii due to the exposure to the various conditions. The Ultimate Tensile Strength (UTS) and the Elastic Modulus were measured and compared with the control dry specimens. At the end of this study, all specimens that were exposed to moisture suffered a loss in mechanical properties, mainly in the Elastic Modulus. It was observed that the specimens with higher moisture content and exposed to higher temperatures over a longer period experienced a greater degree of loss. Overall the analysis and discussion from the acquired data aim to serve as a guide to predict the performance of BMI Resin Composites undergoing water diffusion.