Towards Reliability-Enhanced Mechanical Characterization of Non-Crimp Fabrics: How to Compare Two Force-Displacement Curves against a Null Material Hypothesis

Detailed characterization of fabric reinforcements is necessary to ensure the quality of manufactured composite parts, and subsequently to prevent structural failure during service. A lack of consensus and standardization exists in selecting test methods for the mechanical characterization of fabrics. Moreover, in reality, during any experimentation there are sources of uncertainties which may result in inconsistencies in the interpretation of data and the comparison of different testing methods. The aim of this article is to show how simple statistical data analysis methods may be used to enhance the characterization of composite fabrics under individual and combined loading modes while accounting for inherent material/test uncertainties. Results using a typical glass non-crimp fabric (NCF) show that, statistically, there are significant differences between the warp and weft direction responses of a presumably balanced NCF under all deformation modes, with weft yarns being generally stiffer. Moreover, the statistical significance of warp-weft couplings under both simultaneous and sequential biaxial-shear loading modes became statistically evident, when compared to a pure biaxial deformation.

Hot-pressed graphene nanoplatelets or/and zirconia reinforced hybrid alumina nanocomposites with improved toughness and mechanical characteristics

This work explains the synergistic contribution of graphene nanoplatelets(GNP)and zirconia ceramic nanoparticles(ZrO2)on the microstructure,mechanical performance and ballistic properties of the alumina(Al2O3)ceramic hybrid nanocomposites.Over the benchmarked monolithic alumina,the hotpressed hybrid nanocomposite microstructure demonstrated 68%lower grain size due to grain pinning phenomenon by the homogenously distributed reinforcing GNP(0.5 wt%)and zirconia(4 wt%)inclusions.Moreover,the hybrid nanocomposite manifested 155%better fracture toughness(KIC)and 17%higher microhardness as well as 88%superior ballistic trait over the monolithic alumina,respectively.The superior mechanical and ballistic performance of the hybrid nanocomposites was attributed to the combined role of zirconia nanoparticles and GNP nanomaterial in refining the microstructure and inducing idiosyncratic strengthening/toughening mechanisms.Extensive combined electron microscopy revealed complicated physical interlocking of the GNP into the microstructure as well as excellent bonding of the GNP with alumina at their interface in the hybrid nanocomposites.We also probed the efficiency of the pull-out and crack-bridging toughening mechanisms through proven quantitative methods.Based on the information extracted from the in-depth SEM/TEM investigation,we outlined schematic models for understating the reinforcing ability as well as toughening mechanisms in the hybrid nanocomposites and meticulously discussed.The hot-pressed hybrid nanocomposites owning high toughness and hardness may have applications in advanced armor technology.

Electrodes based on nano-tree-like vanadium nitride and carbon nanotubes for micro-supercapacitors

Vanadium nitride （VN） was deposited by DC-sputtering on a vertically aligned carbon nanotube （CNTs） template for the purpose of nano-structuration. This led to the fabrication of hierarchically composite electrodes consisting of porous and nanostructured VN grown on vertically aligned CNTs in a nano-treelike configuration for micro-supercapacitor application. The electrodes show excellent performance with an areal capacitance as high as 37.5 mF cm^-2 at a scan rate of 2 mV s^-1 in a 0.5 M K2504 mild electrolyte solution. Furthermore, the capacitance decay was only 15% after 20,000 consecutive cycles. Moreover, the capacitance was found to increase with VN deposit thickness. The X-ray photoelectron spectroscopy analyses of the electrodes before and after cycling suggest that the oxide layers that form at the VN surface is the responsible for the redox energy storage in this material. Such electrodes can compete with other transition metal nitride based electrodes for micro-supercapacitors.

Facile synthesis of ironenickelecobalt ternary oxide(FNCO)mesoporous nanowires as electrode material for supercapacitor application

Transition Metal Oxides have drawn significant attention due to their reversible chemical redox reaction and long-life stability.Inexorable agglomeration and shrinkage/expansion of transition metal oxides in the nanosize regime have a noticeable effect on their electrochemical properties.Here in this work,mesoporous nanowires(NWs)with a typical composition of iron-nickel-cobalt ternary oxide(FNCO)are synthesized using a simple,facile and cost-effective hydrothermal process followed by furnace annealing.These NWs are then extensively investigated as an electrode material for supercapacitor application.To compare the electrochemical properties,nanowires of nickel-cobalt oxide(NCO),iron-cobalt oxide(FCO)and cobalt oxide(CO)were also produced by following the same protocol.The FNCO NWs are found to overcome the shortcomings in the electrochemical energy storage devices by exhibiting higher values of specific capacitance(2197 Fg^(-1))and energy density(109 Whkg^(-1))at 1 Ag^(-1) current rate.Moreover,the FNCO NWs also showed a cyclic charge/discharge stability of 96%even up to 20,000 cycles.Furthermore,a FNCO//graphene asymmetric device,fabricated with FNCO NWs and graphene as positive and negative electrodes,respectively,which exhibit high energy density(47 Whkg^(-1)),power density(375 Wkg^(-1))and excellent capacitance retention(86%)after 15,000 cycles.