Study On The Damping Properties Of Graphene-AL Nanolaminated Composites

An effective way to improve the mechanical properties of metallic materials is to form metal matrix composites(MMCs).By adding high property reinforcing phase(particles,whiskers,fibers,and etc.)into the metal matrix,not only the mechanical properties of metal matrix can be improved,some new functional properties can also be acquired.In other words,MMCs may combine the advantages of both constituents(metal matrix: good ductility,formability and so on;reinforcement: high hardness,high elastic modulus and so on),leading to their wide industrial applications.In actual applications,structural components made by MMCs may work under complicated loading conditions,where considerable mechanical vibration and noise may be generated.These mechanical vibrations and noise are not only detrimental to the physical health and mental wellbeing of the users,but would also affect the precision and stability of the components,leading to their performance degradation or even complete malfunction.Therefore,the components used in such situations require excellent anti-noise and shock-absorbing properties.In this context,it is necessary to fabricate MMCs with good mechanical and damping properties.Our team has previously developed graphene-reinforced Al matrix composite with a bioinspired nanolaminated microstructure.These RGO-Al composites were found to possess remarkable strength and ductility synergy under uniaxial tensile loading.The effective load transfer between RGO and the Al matrix rationalized such a significant strengthening and toughening effect.The mechanical properties of the bioinspired nanolaminated aluminum composites have been extensively investigated by various groups,while few research has been conducted on their damping properties.This limits the further application of these composites under complex load conditions.Based on the samples of nanolaminated RGO-Al composites,RGO-Al composite and pure Al micro-pillars were prepared on the bulk samples surface.One-time compression and cyclic loading compression tests were conducted on these micro-pillars within FIB and the mechanical properties and damping properties of these micro-pillars were measured.The addition of RGO significantly improved the compression strength of RGO-Al composites.The engineering strain of RGO-Al micro-pillars were remarkably smaller than pure Al micro-pillars in both one-time compression and cyclic loading compression tests.Furthermore,the composite pillars possessed three times higher damping coefficient than their pure Al counterpart.TEM samples of these deformed micro-pillars were fabricated and the dislocation density near the lamella interfaces of these micro-pillars were measured.The results showed that the dislocation density near RGO/Al interface was 45% greater than that near the inter-lamella boundary of pure Al samples despite the plastic strain of RGO-Al composites was approximately 40% less than that of pure Al pillars.These results revealed that RGO nanosheets at the inter-lamella boundaries effectively impeded dislocation motion during deformation and resulted in greatly enhanced dislocation accumulation inside the Al grains.These dislocations worked as damping sources during the cyclic loading compression test and led to a much higher damping capacity of RGO-Al composite pillars than that of pure Al pillars.In addition,the reliability of the micro-size damping test method was confirmed by traditional macro-size damping test,where the damping coefficients shared the same order of magnitude as those measured from in situ microscopic tests.This work proves that the addition of graphene can significantly improves the mechanical properties and damping properties of nanolaminated composites,and provides a new and simple approach to study the damping properties of structural materials.