Effect of seawater on tensile and shear properties of composite material

• Main Author: Loh, Shao Hui
• Other Authors: Seah Leong Keey
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Materials::Composite materials
• Online Access: http://hdl.handle.net/10356/64108
• Institution: Nanyang Technological University

This paper investigated the effect of moisture on the mechanical properties of glass fibre/bismaleimide composites. Specimens were immersed into simulated seawater baths at 30, 50 and 80˚C respectively and their weights were periodically recorded. The diffusion of the composite type was also obtained and compared. Tensile and shear tests were conducted on dry and soaked specimens in several configurations. Scanning electron microscopy was employed to study them. Results obtained showed that an increase in temperature accelerated the rate of moisture absorption. The creation of additional voids in the specimens was plausibly due to the effect of elevated temperatures. Fickian equilibrium was evident for specimens immersed in the 50 and 80˚C baths, while data from the 30˚C bath showed continual weight increments. A second stage diffusion behaviour was not observable. Data showed that the absorbed moisture degraded the tensile and shear properties of the specimens. The drop in shear properties was more significant than that of tensile properties. The slight drop in tensile performance plausibly resulted from the weakening of the matrix and interfacial bonding between fibres and matrix, while the moisture-resistant fibres continued to bear the load. As the 0˚ fibres were not utilised, the load was only distributed between the 90˚ fibres and the weakened matrix, hence resulting in a larger drop in shear properties. The disappearance of resin on the fibres, observed from SEM micrographs, was consistent with the tensile data. The slight degradation effect in mechanical properties recommended extended immersion duration to observe further changes in properties.