Study on molding control factors to reduce void contents in manufacturing CFRP parts by HP-RTM

Abstract

Research and development efforts are ongoing to apply Carbon Fiber Reinforced Plastic (CFRP) to the automotive industry for weight and exhaust gas reduction. Among the available manufacturing processes, High Pressure Resin Transfer Molding (HP-RTM) stands out as the most suitable for mass production due to its cost efficiency, cycle time, and moldability. However, concerns over void formation and quality reliability have limited its application in Advanced Air Mobility (AAM). This study investigates control factors that can reduce void content in CFRP parts manufactured via HP-RTM. By comparing classical Resin Transfer Molding (RTM) with HP-RTM, a key control factor is identified, and changes in void content and static properties are observed across varying factors. The study concludes that while increasing molding pressure minimally affects absolute void content, it slightly increases relative void content due to reduced product thickness. Additionally, higher internal release agent content and resin injection velocity increase void formation due to altered flow dynamics. However, using a nip edge reduces void size and variation, ensuring more consistent product quality. By optimizing key factors such as vacuum, normal pressing force, and injection parameters in HP-RTM, void content can be consistently maintained at 1 % or lower. These findings will contribute to the practical application of HP-RTM in the AAM industry and provide valuable insights into the manufacturing process of CFRP parts.