According to the latest report, the next generation of composite materials can monitor their own structural health status, and become common.
Carbon fiber composites are light and sturdy and are important structural materials for automobiles, aircraft and other means of transport. They consist of polymer substrates, such as epoxy resins, which are embedded with reinforced carbon fibers. Due to the different mechanical properties of the two materials, the fibers will fall off the substrate under excessive stress or fatigue. This means that damage to the carbon fiber composite structure may still be hidden below the surface and cannot be detected by the naked eye, which can lead to catastrophic failure.
“By understanding the inside of the composites, you can better judge their health and know if there is any damage that needs to be repaired,” Ridge Chris Bowland, a researcher at the
Oak Ridge National Laboratory at the U.S. Department of Energy (Oak National Laboratory) Wigner. ”Recently, Amit Naskar, head of the carbon and composites team at Bowland and ORNL, invented a rolling stripe method to wrap conductive carbon fibers on semiconductor silicon carbide nanoparticles. The nanomaterials are embedded in composite materials that are stronger than other fiber-reinforced composites and have a new ability to monitor the health of their own structures. When enough coated fibers are embedded in the polymer, the fibers form a power grid, and the bulk composites conduct electricity. Semiconductor nanoparticles can destroy this electrical conductivity under the action of external forces, adding mechanical and electrical functions to the composites. If the composites are stretched, the connectivity of the coated fibers will be destroyed and the resistance in the material will change. If the storm turbulence causes the composite wing to bend, an electrical signal may warn the plane’s computer to indicate that the wing is under too much pressure and suggest a test. The rolling strip demonstration of ORNL proves in principle that the method can produce the next generation of composite coated fibers on a large scale.Self-sensing composites, perhaps made from renewable polymer substrates and low-cost carbon fibers, can find their place in ubiquitous products, including even 3D printed cars and buildings. In order to make fibers embedded in nanoparticles, the researchers installed high-performance carbon fiber spools on the rollers, and the rollers soaked the fibers in epoxy resins, which contain available nanoparticles on the market, the width of which is about the width of the virus (45-65 nm).
The fibers are then dried in the oven to secure the coating. In order to test the strength of the fibers embedded in nanoparticles glued to the polymer substrate, the researchers made fiber-reinforced composite beams, which were arranged in One Direction.The Bowland carried out a stress test in which the ends of the cantilever were fixed, while the machine evaluating the mechanical properties applied thrust in the middle of the beam until the beam failed. In order to study the sensing capability of the composite material, he installed electrodes on both sides of the cantilever beam. In a machine known as a “Dynamic mechanical analyzer,” he clipped one end to keep the cantilever stationary. The machine exerts force at the other end to bend the suspension beam while Bowland monitors the change of resistance. ORNL, a postdoctoral researcher Ngoc Nguyen, conducted additional tests in the Fourier Transform Infrared spectrometer to study chemical bonds in composites and improve understanding of the enhanced mechanical strength observed. The researchers also tested the ability of the dissipative energy of composites made of different quantities of nanoparticles (measured by vibration damping behavior), which would facilitate the response of structural materials to shocks, vibrations and other stress and strain sources. At each concentration, nanoparticles can enhance energy dissipation (from 65% to 257% to varying degrees). Bowland and Naskar have applied for a process patent for the manufacture of self-sensing carbon fiber composites.
“Impregnated coatings provide a new way to take advantage of new nanomaterials that are being developed. “Bowland said. The study was supported by research and development projects directed by the ORNL Laboratory, published in the journal ACS Applied Materials and Interfaces (Applied Materials & Interfaces) of the American Chemical Society.
Post time: Dec-07-2018