Fabrication and characterization of a carbon fiber/ epoxy composite reflector antenna

Abstract

Antennas are crucial elements in communication technology, serving as the interface between transmission lines and free space to facilitate signal transmission and reception. Various antenna types are deployed across different applications, each tailored to specific needs such as frequency, bandwidth, radiation pattern, and polarization. Reflector antennas, in particular, are highly valued for their capacity to focus electromagnetic waves, thereby enhancing signal strength and directivity. These antennas are extensively utilized in satellite communications, radio telescopes, and radar systems where high gain and precise radiation pattern control are essential. Reflector antennas generally feature a parabolic-shaped reflector that channels incoming or outgoing electromagnetic waves to or from a focal point. Their primary advantage lies in their ability to achieve high directivity and gain, making them ideal for long-distance communication and high-resolution imaging. Designing a reflector antenna involves meticulous consideration of factors like the reflector's shape and size, the materials used, and the feed mechanism's integration. The material choice for reflector antennas is pivotal in determining their performance, durability, and weight. Traditional materials such as aluminum and steel are commonly used due to their excellent electrical conductivity, ease of fabrication, and relatively low cost. However, these materials have limitations, including a higher weight and vulnerability to deformation under mechanical and thermal stresses. As the need for high-performance, lightweight, and durable antennas grows, attention has shifted to advanced composite materials, notably carbon fiber-reinforced polymers (CFRP). Carbon fiber-reinforced polymer matrix polymer (CFRP) has remarkable mechanical qualities, including low density, stiffness, and high tensile strength. By binding the fibers together, the polymer matrix gives them resilience and form. This combination makes CFRP an ideal material for applications requiring weight reduction and high structural performance. For reflector antennas, CFRP offers numerous advantages over conventional materials. A key benefit of using CFRP in reflector antennas is the significant weight reduction. This is especially critical in satellite and aerospace applications, where reducing weight translates to substantial cost savings and enhanced performance. CFRP's low density enables the construction of large reflector antennas without the weight burden associated with metals like aluminum or steel. This weight reduction also simplifies structural design and assembly requirements, enhancing overall system efficiency. Another crucial advantage of CFRP is its high strength-to-weight ratio. The carbon fibers impart high tensile and compressive strength to the composite, allowing the reflector to maintain its shape and structural integrity under various loads and environmental conditions. This thesis explores the fabrication and characterization of a carbon fiber/epoxy composite reflector antenna, detailing the comprehensive process from material selection to final performance evaluation. The study starts with the material selection, with a focus on carbon fiber-reinforced polymer (CFRP) because of its excellent strength-to-weight ratio, lightweight design, and exceptional mechanical qualities. To identify the optimal configuration, carbon fibers were oriented at various angles, and ANSYS simulations were conducted for three different orientations to assess their performance under anticipated load conditions. To fabricate the CFRP specimens, the prepreg sheets were stacked in a predetermined order and orientation. A reflector model was created, with a total thickness of 24 millimeters and a thickness of 0.2 millimeters for each layer. ANSYS was used to analyze the stacking sequence at various angles, including 0°/90°, 45°/0°, and 30°/0°/60°/0°/90°/0°/0°/0° to ascertain the impact of fiber orientation on the material's structural performance. Because of its balanced strength and structural stability, the 0°/90° orientation was found to be the most appropriate, and it was chosen for final fabrication. In this research, both CFRP and aluminum alloy 6061-T6 were employed to examine the structural integrity and performance of an antenna reflector under different loading conditions. CFRP was specifically chosen for its excellent strength-to-weight ratio and remarkable mechanical properties, utilizing the VTP H 300 CFA 210 3KT RC42 HS carbon fiber prepreg. This material weighs 210 g/m^2 and contains 42% epoxy content. The manufacturing process involved layering eight carbon fiber layers, followed by a foam core, and then another eight carbon fiber layers. This sandwich structure was selected to enhance mechanical properties while minimizing weight. The layers were cured in an autoclave, a high-pressure oven that applies heat and pressure to eliminate voids and ensure proper adhesion between the layers, enabling the composite to achieve the desired strength and durability. Following production, the CFRP reflector sample underwent a comprehensive characterization process to verify its performance against design requirements. The characterization included various mechanical and electromagnetic tests. Tensile and shear tests were conducted to evaluate the mechanical properties of CFRP and confirm its high strength and stiffness. The integrity of the epoxy matrix was confirmed, and its chemical composition was examined using Fourier transform infrared spectroscopy (FTIR). To evaluate the antenna's performance in terms of signal transmission and reflection, radio frequency (RF) tests were done. These RF measurements were crucial in evaluating the reflector's performance in its intended application and were conducted in an anechoic chamber to prevent external electromagnetic interference. The performance of the CFRP reflector was compared to that of a conventional aluminum reflector. The CFRP reflector demonstrated superior RF performance, with better signal strength and clarity, attributed to its precise shape and material properties that reduce signal loss and distortion. Additionally, the weight comparison underscored one of the significant advantages of using CFRP. The CFRP reflector weighs approximately 650 kg, significantly lighter than its aluminum counterpart, which weighs around 1.2 tonnes due to its frame and structural components. This substantial weight reduction translates to easier handling, lower launch costs for satellite applications, and reduced structural stress during deployment and operation. These results show that the use of CFRP for reflector antennas not only reduces the overall weight but also improves the antenna performance, making it a more advantageous choice compared to conventional aluminium structures. The detailed analysis and successful implementation of a 7.3 m CFRP reflector antenna in this study is a testament to the material's capabilities and potential in the field of communications technology. The comprehensive approach, ranging from material selection and simulation to fabrication and characterization, provides valuable insights and lays a strong foundation for future developments in the use of advanced composites in high-performance engineering applications. In conclusion, this thesis concludes that the application of carbon fibre composites in reflector antennas represents a significant advance in antenna technology and offers a lightweight, high-strength alternative that meets the stringent demands of modern communication systems.