Mechanical And Microwave Absorbing Properties For Graphene And/or Carbon Nanotube/Continuous Carbon Fiber Reinforced Epoxy Resin Nanocomposites

Graphene, a single-layer carbon sheet of sp2-hybridized carbon atoms arranged in a hexagonal packed lattice structure, has received world-wide attention due to its extraordinary electronic, thermal and mechanical properties. Accordingly, graphene has been widely used as reinforcing fillers for polymers to form structural and functional nanocomposites. Covalent modification on the surface of graphene is an indispensable strategy for the practical application of graphene-based polymer nanocomposites, which is an effective method for improving the interfacial interactions between graphene and polymer matrix. Synergetic effect, nanoscale effect and composite effect between the 1-D and 2-D nano materials result in improving the mechanical properties and thermal conductivity of nanocomposites. In addition, stable two-dimensional structure, high specific surface area, excellent electrical conductivity make graphene is expected to become the ideal of the electromagnetic wave absorption material, which could meet the requirements of the broadband, strong absorption, thin, lightweight, low density, good thermal stability, etc. Meanwhile, incorporation conduction loss absorbing materials (graphene) and magnetic loss absorbing material (carbonyl iron powder, CIP) can make up for impedance matching decline caused by high carrier mobility of graphene, improve the microwave absorbing property of nanocomposites.1. Graphene (GNS) was mass-produced from flake natural graphite by chemical oxidation, high temperature-rapid expansion and ultrasonic treatment. The influence of ultrasonic time on morphology, structure and mechanical properties for graphene/epoxy nanocomposites (GNS/EP) were systematically investigated. As a result, when ultrasonic time was 15 h, graphene has a better disperse state in epoxy matrix, resulting in enhancement of mechanical property for graphene/epoxy nanocomposites.2. In order to improve the reactivity of graphene in epoxy resin reactivity, GNS was modified with NH3H2O and H2O2 to obtain amine (-NH2) modified graphene (AMGNS). And then we characterized the structure morphology of AMGNS and studied the influence of its content on the mechanical properties, thermal performance and microwave absorbing property for epoxy-based nanocomposites. As a result, when the content of AMGNS was 0.1 wt%, the flexural strength and impact strength for AMGNS/EP nanocomposites were increased by 94.4% and 34.3%, compared with EP, respectively. When the content of AMGNS was 0.5 wt%, the tensile strength and Tg for AMGNS/EP nanocomposites were increased by 27.8% and 5.74%, compared with the EP, respectively. When the content of AMGNS was 1.0 wt%, the thermal conductivity for AMGNS/EP nanocomposites were increased by 21.9% and 5.74%, compared with the EP, respectively. When the content of AMGNS was 3.0 wt%, AMGNS/EP nanocomposites presented a minimum reflectivity of-36.05 dB and the effective absorption bandwidth (<-10dB) could cover 10.83-18.00 GHz with matching thickness of 2.4 mm.3. Ammonia-modified graphene/carbon fiber reinforced epoxy resin unidirectional composite (AMGNS-CF/EP) were prepared by using a facile blend method. When the content of AMGNS was 0.3 wt%, the flexural strength and flexural modulus for AMGNS-CF/EP unidirectional composites were increased by 10.4% and 7.04%, compared with carbon fiber reinforced epoxy composites (CFEP), respectively. When the content of AMGNS was 0.5 wt%, the ILSS and Tg for AMGNS-CF/EP unidirectional composites were increased by 8.76% and 9.62%, compared with CFEP unidirectional composites, respectively.4. Co-reinforcement with AMGNS and carbon nanotube (MWCNT) could effectively prevent the agglomeration of AMGNS and MWCNT, resulting in the enhancement of mechanical properties for the AMGNS-MWCNT/EP nanocomposites. As a result, when each of the content of AMGNS and MWCNT was 1.0 wt%, the tensile strength and flexural strength for AMGNS-MWCNT/EP nanocomposites were increased by 20.7% and 55.5%, compared with EP, respectively. And then we prepared ammonia-modified graphene-carbon nanotube/carbon fiber reinforced epoxy resin (AMGNS-MWCNT/CFEP) unidirectional composites by using a facile blend method. As a result, when each of the content of AMGNS and MWCNT was 0.5 wt%, the flexural strength and ILSS for AMGNS-MWCNT/CFEP unidirectional composite were increased by 12.5% and 10.1%, compared with CFEP unidirectional composites, respectively.5. Ammonia-modified graphene-CIP/paraffin (AMGNS-CIP/paraffin) nanocomposites were prepared by using a facile blend method. As a result, when the content of AMGNS was 1.0 wt%, AMGNS-CIP/paraffin nanocomposites presented a minimum reflectivity of -21.7 dB and the effective absorption bandwidth (<-10dB) could cover 2.43-4.00 GHz with matching thickness of 4.0 mm. Then we prepared Ammonia-modified graphene-CIP/epoxy nanocomposites (AMGNS-CIP/EP) by using a facile blend method. Co-incorporation graphene and CIP can improve the microwave absorbing property of nanocomposites. As a result, when the content of AMGNS was 3.0 wt%, AMGNS-CIP/EP nanocomposite presented a minimum reflectivity of -36.82 dB and the effective absorption bandwidth (<-10dB) could cover 11.35-17.83 GHz with matching thickness of 1.9 mm.