Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150762

150762 - Rapid Fabrication of Carbon Fiber Reinforced Epon-Based Epoxy Resin Composites via Hot Press-Triggered Frontal Polymerization 

In the realm of advanced composite materials, the pursuit of sustainable and efficient manufacturing processes is crucial, particularly in industries such as aerospace, automotive, and energy. Traditional manufacturing techniques for thermoset-based carbon fiber reinforced polymers (CFRPs) often require lengthy cure cycles and high energy consumption, primarily relying on autoclave processes that pose significant environmental and economic burdens. Frontal polymerization (FP) emerges as a promising alternative, characterized by its rapid curing and energy-efficient attributes. FP involves a self-propagating reaction initiated by a localized heat source that polymerizes a monomer or resin system across the material length, significantly reducing processing time and energy expenditure by up to 90%.

Acrylate resin systems, known for their high reactivity, are highly suitable for FP, unlike the more challenging epoxy resin systems commonly used in the industry. Frontal ring opening metathesis polymerization (FROMP) is utilized to cure poly(dicyclopentadiene) (pDCPD) resin, and it was found that acrylate-based resins can achieve mechanical strengths similar to conventionally oven-cured specimens. However, pDCPD resin's limited pot life restricts its commercial applications. On the other hand, epoxy-based monomers are favored for CFRP fabrication due to their extended pot life. Radical-induced cationic frontal polymerization (RICFP) with dual initiator systems has made FP of epoxy resin possible, prolonging resin stability and improving mechanical characteristics, as demonstrated for bisphenol A diglycidyl ether (BADGE) resin and other studies for 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ECC) resin. These studies highlight the potential for higher efficiency and mechanical performance in industrial RICFP applications, especially with dual initiation systems that enhance front polymerization characteristics, such as degree of cure, front velocity, and degree of cure.

The success of frontal polymerization process in fiber-reinforced polymers (FRPs) relies on precise control over local heat flow, including resin reaction heat, thermal diffusion, and heat losses. Balancing fiber volume fraction (V_f) and activation energy is crucial, especially at higher V_f, to prevent insufficient activation energy and early quenching of the reaction front. Laboratory-scale RICFP can achieve V_f up to 35-40%, while FROMP techniques can reach 50-60%. Improving FRP use in industrial processing requires modifying elements and strategies like creating quick-reacting initiators, optimizing resin mixtures, or minimizing heat losses to improve heat retention, though these methods may increase energy consumption, potentially offsetting FP's low-energy benefits. Most CFRP fabrication studies use vacuum bagging techniques, complicating the process to reduce heat loss and maintain successful FP. The high exothermic heat during FP due to dual initiator systems can cure commercial industrial epoxy resin, such as BADGE or EPON. Mixing frontal resin with commercial industrial epoxy resin can scale up FP for practical commercial use, combining the enhanced mechanical strength and longer pot life of industrial epoxy resins with the quick curing capabilities of frontal resin. This hybrid resin system enhances composite material quality and durability while speeding up manufacturing processes, meeting high industry standards in a cost-effective and ecologically friendly manner. Thus, a hybrid resin system addresses the challenge of balancing manufacturing speed with the quality and performance of modern composites.

We propose an innovative approach using a combination of frontal resin and EPON-based epoxy resin to manufacture unidirectional CFRP laminates through hot press thermal-triggered frontal polymerization (HPFP). HPFP simplifies the experimental setup compared to existing vacuum bagging methods and ensures full composite curing. We demonstrate the feasibility of producing FRPs with fiber volume fractions up to 50-60%, surpassing the 32-45% achieved with UV-induced FP and vacuum bagging, previously. The mixture preparation involves mixing the frontal resin with EPON epoxy resin with 1:0.3 ratio and varying the photoinitiator (PI) content from 0.4 wt% to 0.7 wt%. The curing process is conducted at 200°C for five minutes, followed by gradual cooling to room temperature. The HPFP method not only simplifies the manufacturing setup but also ensures a uniform thickness and quality of the laminates, overcoming the challenges of uneven thickness and incomplete curing often encountered in UV-induced method. In this research, we characterize the FP process and the impact of photoinitiator weight content and fiber volume fraction on flexural strength and modulus. We compare the flexural properties of FRPs fabricated using conventional oven-curing method, neat frontal resin-based laminates, and neat EPON-based laminates.

By carefully controlling the initiator content and the thermal conditions, we achieved significant improvements in the flexural strength of the CFRP laminates. For instance, laminates with 60% V_f exhibited up to a 36% increase in flexural strength with the increment of PI content from 0.6 wt% to 0.7 wt%. Moreover, the hybrid resin system demonstrated superior performance compared to both EPON-based and neat frontal resin-based laminates. The HPFP-fabricated hybrid laminates exhibited a 42% higher flexural strength than the EPON-based laminates and a 14% higher flexural strength than the neat frontal resin-based laminates. This hybrid approach not only addresses the need for rapid and efficient processing but also ensures high-quality composite materials that meet industry standards.

In conclusion, the HPFP method for CFRP fabrication presents a sustainable and efficient alternative to traditional curing techniques. Its ability to produce high-performance composites with improved flexural properties and reduced processing times highlights its potential for widespread use in various industrial applications. This study sets the stage for future advancements in additive manufacturing and repair techniques for thermoset and thermoset-based fiber composites, offering a pathway to more eco-friendly and cost-effective production processes.

Presenting Author: Amirreza Tarafda Syracuse university

Presenting Author Biography: Amirreza received his Master's degree in Mechanical Engineering Applied Mechanics from Tarbiat Modares University (Iran) in 2021 and his Bachelor's degree in Mechanical Engineering Applied Mechanics from Isfahan University of Technology (Iran) in 2018. Amirreza joined the Composite Materials Lab in September 2022. His research focuses on the advanced manufacturing of fiber-reinforced polymer matrix composites.

Authors:

Amirreza Tarafda Syracuse university
Yeqing Wang Syracuse university