Carbon nanotubes (CNT) has a very excellent strength and stiffness. The advantages of carbon nanotubes can be applied to an attractive prospect in the field of macro-engineering. However, numerous studies have found that since the CNT determines its size only as a non-continuous fibers in a matrix, and the effects of poor load transfer between the CNT and the substrate. Thus, a new way of CNT applications have been proposed, namely by the CNT, the traditional continuous fiber and matrix composition of multi-scale hybrid composites to effectively utilize CNT excellent mechanical properties. This material is known as CNT enhanced multi-scale matrix hybrid composites.
CNT reinforced matrix, multi-scale hybrid laminates made of composite materials, both excellent fiber dominated mechanical properties, but also good mechanical properties of the dominant matrix that is suitable for inter-layer load and shock load environments more frequent, such as aviation Spacecraft special environment in which the load; and the application of this composite material in some large holes in the laminate structure, help to improve the strength and fatigue life of the surrounding holes, thereby enhancing the structure and security of the connection. Therefore, the carbon fiber / CNT enhanced multi-scale hybrid composite matrix has become the new frontier in the field of materials research hot spot.
CNT reinforced matrix, multi-scale hybrid composites
Mixing CNT in the matrix can be increased difference in mechanical properties between the fracture toughness, stiffness and strength, balanced matrix continuous fiber reinforced matrix and reinforcing fibers. Improve the mechanical properties of the matrix control, making composite materials fracture toughness; interlaminar shear strength and mechanical properties perpendicular to the inner surface of the continuous fiber direction are greatly improved. However, due to the size of the characteristics of CNT, CNT reinforced so that the mechanical properties of the composite material far less than people expected better.
Many nature biocomposite also belongs to multiscale hybrid composites, such as animal bones, its composition contains a macro component, microscopic and nanoscopic components composition, elements of these different scales ingredients makes bones with high toughness and high stiffness. Inspired corresponding synthetic multiscale composites (with Nano reinforcing phase) have been proposed, there is a multi-scale component so that it has excellent physical and mechanical properties.
CNT properties:
Carbon nanotubes are significantly better than traditional materials in mamy aspect. Treacy and Wong et al found that single-walled and multi-walled carbon nanotubes axial Young’s modulus of up 1TP or more (up to 4.15TPa), and a tensile strength of 100 ~ 200GPa. Yu et al study demonstrated nanotubes having good ductility, in up to 12 percent prior to tensile failure. Vigolo carbon nanotubes and other woven fibers, which have very good flexibility, fracture does not occur it a knot. Carbon nanotubes also have a strong current carrying capacity and thermal conductivity.
CNT matrix composites
The presence of CNT matrix composite material of carbon nanotubes increases the matrix micro crack propagation resistance, thanks to the bridging mechanism of carbon nanotubes. Gojny found that an epoxy resin with 0.5% by weight of amino-functionalized double-walled carbon nanotubes can improve the fracture toughness of 43%. Yu et al epoxy joined the multi-walled carbon nanotubes 1% and 3% by weight, improves the fracture toughness of 29% and 62%; at 8.67MPa and stress amplitude 11.56MPa of 0.5% by weight of multi-walled carbon nanotube / epoxy composites bending fatigue life is 10.5 times the fatigue life of the epoxy resin and 9.3 times. Zhou and other studies of four kinds of weight content (0.1%, 0.2%, 0.3% and 0.4%), multi-walled carbon nanotubes to enhance the mechanical properties of epoxy composites Epon862, the results showed that 0.4% multi-walled carbon nanotube composites Young’s modulus maximum strength and fracture toughness of the strongest 0.3%, indicating that it will not increase the mechanical properties and CNT content and continue to improve. Fiedler other studies confirmed amino-functionalized CNT to epoxy resins open fracture toughness (KIC) has significantly enhanced the effect of the epoxy resin, 0.3% by volume content of amino functional DWCNTs so open fracture toughness increased by 45%. Cadek and other studies show that multi-walled carbon nanotube reinforced polymer composites not only have good mechanical properties and good dispersion in the matrix. Zou and other studies of the epoxy-functionalized MWNTs reinforced epoxy composite, which can effectively improve the tensile strength and tensile modulus. Breton and other surrounding MWCNT reinforced epoxy composite mechanical properties a study and found that the weight content of CNT composites 6% less than the tensile strength of the tensile strength of the CNT content of 3%. However, the CNT load transfer between the substrate and the CNT Central African continuous fibers and the matrix effect is not good, CNT composites reinforced stretch, compress limited mechanical properties of stiffness and strength.