Tensile tests of composite coupons with prescribed porosity

• Main Author: Seah, Sin Wei.
• Other Authors: Chai Gin Boay
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Aeronautical engineering::Materials of construction
• Online Access: http://hdl.handle.net/10356/54194
• Institution: Nanyang Technological University

The applications of carbon fibre reinforced polymers (CFRP) are gaining momentum in the aerospace and automotive industries. The great strength-to-weight ratio provided by CFRP had helped not only to reduce the weight, but also the costs through lower fuel consumption. Porosity, which is a common defect that can occur during the manufacturing process, affects the properties of CFRP greatly. Therefore, this project aims to determine how does varying porosity level affects the tensile properties of CFRP. In this project, a wet-layup process was adopted to manufacture the specimens. Varying porosity level of the specimens was achieved by placing the resin and hardener mixture into vacuum pressure chamber, subjecting it to varying vacuum pressure. The measurement of void content was done through microscopic analysis and ImageJ software. However, no direct relationship was able to be established between the porosity level and vacuum pressure used even though different porosity level was produced. Results have shown that tensile properties, such as the ultimate tensile strength (UTS), tensile modulus and strain energy, decreases in magnitude when porosity level increases. As the porosity level decreases from 7.56% to 3.38%, the UTS increases by approximately 19.6%, while the tensile modulus only increases by approximately 12.7%. This shows that the tensile modulus is less sensitive than that of UTS when the void content of CFRP is varied. However, when the void content decreases below 3.38% to 2.06%, the UTS and tensile modulus remain almost constant, fluctuating by approximately ±1.0%. This can be due to the high fibre volume ratio of the specimen, which can be looked into in the future.