In a significant scientific breakthrough, researchers from the U.S. Department of Energy's Oak Ridge National Laboratory (ORNL) have developed a new method to strengthen carbon fiber composites. Published in Advanced Functional Materials, their research details how carbon nanofibers can drastically improve the bond between carbon fibers and their surrounding polymer matrix, leading to materials that are both stronger and tougher.
Addressing a long-standing industry challenge, the ORNL team, led by Sumit Gupta, has leveraged a hybrid technique that heightens chemical and mechanical bonding, resulting in a significant enhancement of material properties. "The challenge of improving adhesion between carbon fibers and the polymer matrix that surrounds them has been a concern in industry for some time, and a lot of research has gone into different approaches," Gupta told ORNL. The team's approach, combining mechanical and chemical bonding, has yielded a 50% improvement in tensile strength and a near doubling of material toughness.
Electrospinning, a technique utilizing a strong electric field to create strands of polyacrylonitrile, plays a central role in this advancement. The process, carefully controlled by the researchers, allows for the production of nanofibers that facilitate improved bonding at the interface of carbon fibers and the polymer matrix. The study has demonstrated that by manipulating variables in the electrospinning process, such as the electric field's strength and the receiver drum's speed, a significant impact on the fibers' performance can be achieved.
Further emphasizing the importance of this research, ORNL researcher Chris Bowland explained the comprehensive approach the team undertook to forge a deeper understanding of the process. "We developed this process in 2023 but have been focused lately on optimizing it and fully understanding the physical processes that enable these improvements," Bowland said in a statement. Control over electrospinning conditions has not only improved the binding of these materials but has also shed light on the types of chemical bonding and the orientation of the fibers formed.
As the team eyes industrial partnerships to bring this technique to the larger market, their goal is to bolster the competitiveness of commercial carbon fiber composites. These materials have broad applications, ranging from automobiles to aerospace and even potential new uses in civil infrastructure and defence. With a patent application filed for their method, ORNL hopes to address cost barriers associated with carbon fiber composites, enabling the use of less material and potentially repurposing shorter, discontinuous fibers.
The research, backed by the DOE Offices of Energy Efficiency and Renewable Energy and Science, underscores ORNL's capacity to blend expertise and tools such as the Frontier supercomputer, X-ray scattering, and NMR imaging to explore material sciences. These resources, crucial for characterizing and understanding material behavior, point towards an era where materials are not only structurally superior but can be tailored finely for a host of different applications. Going forward, the research team plans to refine their electrospinning technique and investigate its implications for other fiber-reinforced composites, including those with self-sensing capabilities.
