Effect of pre-load on diffusion characteristics of composite material

• Main Author: Chew, Xin Yun
• Other Authors: Seah Leong Keey
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/60903
• Institution: Nanyang Technological University

The aim of this project was to study the water absorption properties of the composite when immersed in salt water – the salt water had a salt to water concentration of 3.5%. The composite material being studied in this project was E-glass reinforced BMI. The composites were being subjected to 3 different environments – pre-tensile loading in salt water at room temperature, no pre-loading in salt water at room temperature and lastly, no pre-loading in 80°C salt water. This project consisted of 2 main sections and both will be discussed in this report. The first section was the design and fabrication of the test rig that will be used to exert a tensile force on the composite. The entire design process (chapters 3 and 4) will be discussed in detail in this report. The second section was the study of the water absorption properties of the composite. The experiment will be conducted over a span of 2000 hours and all the composite specimens will be immersed in 3.5% salt water throughout the experiment. The salinity of the saltwater will also be maintained to ensure that the results obtained are accurate. More details will be mentioned in the experimental procedures (chapter 5) section of this report. The report will end off with a section on the discussion of the results attained from the experiments executed. From this project, it was found that a decrease in fiber content, increase in water temperature and/or the existence of a tensile pre-load on the composite will all ultimately result in an increase in rate of water absorption i.e. diffusivity, as well as an increase in the equilibrium water content of the composite. Lesser fiber content will allow for more expansion of the matrix and thus increasing the amount of free volume within the composite to accommodate the water molecules. An increase in water temperature in which the composite is immersed in will lead to mechanical and chemical degradation of the composite structure, while the application of a tensile pre-load on the composite will cause an increase in mechanical degradation of pre-existing voids within the composite structure. Both types of degradation of composite structures will lead to an increase in amount of free volume within the composite, hence allowing more water molecules to diffuse in. A more thorough discussion of the results obtained from the experiments can be found in chapter 6 of this report. This report will be concluded with a chapter on future recommendations.