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Thesis Format

Alternative Format

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Prof. Hrymak, Andrew

Abstract

In recent years, due to growing environmental concerns, composite materials have emerged as a promising lightweight alternative for metals in structural applications in automobiles. Among composite manufacturing processes, Wet Compression Molding (WCM) is a new method of producing Carbon Fiber Reinforced Polymer (CFRP) components. For similar processes like RTM, operating conditions are always one of the factors that impact the mechanical performance of CFRP parts. Thus, this thesis aimed to investigate the effects of operating conditions, including resin temperature, mold temperature, resin set time, gap closure speed, and mold curing time on the mechanical property of the composite parts. In addition, the relationship between the initial resin application and the quality of the final parts was evaluated in this research.

Flat plaques of carbon-fiber composites in an epoxy matrix were fabricated using WCM equipment, and the flexural property (Young’s Modulus) of the final parts were measured. Through statistical analysis, experimental results revealed that the part's mechanical property was significantly affected by the mold temperature, resin temperature, and resin set time. Moreover, at the higher level of the significant factors, the quality of the parts was lower, and the optical microscope test confirmed voids formation during the WCM process (air entrapment), which was the primary reason for the poor quality of the final parts. In addition, statistical results exhibited no correlation between the initial resin distribution and the mechanical property of the final parts.

Summary for Lay Audience

Because of rising regulatory obligations worldwide, the automotive industry has focused on improving automobile fuel efficiency. As a result, the automotive industry began to prioritize weight reduction. Using materials with great strength and low density, such as polymer composites, to reduce the weight of a car is known as “lightweighting.” Wet compression molding (WCM) is a new method of producing Carbon Fiber Reinforced Polymer (CFRP) components in composite manufacturing processes. Since the WCM process is still in its early stages, there are no complete studies about how to improve it. So, the main goal of this study is to understand better which process factors have a significant effect on the WCM process and then investigate the relationship between process and material parameters and the mechanical properties of the composite.

The first part of this research aimed to understand how several operating conditions, such as mold temperature, resin temperature, resin set time, gap closure speed, mold curing time, and sampling area, impact the quality of carbon composite products produced by the wet compression technique. The influence of these process variables on the part quality was statistically investigated; the slope of the stress-strain curve measured by the flexural test was used to indicate the part quality at specific sampling locations. Experimental results showed that the mold temperature, resin temperature, and resin set time were significant variables for improvements in the mechanical property of the parts. In contrast, the effects of mold curing time and gap closure speed on the mechanical property appeared insignificant. In addition to that, it was found that at the higher level of the significant variables, the quality of the produced parts was lower, which was further investigated with an optical microscope test, and void (air entrapment) was observed.

The second part of this research studied the correlation between the initial resin application area and the final part's mechanical property to see if the initial resin distribution is a significant factor in determining part quality. According to the data, there were no statistically significant correlations between the initial resin distribution and the mechanical property of the final parts.

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