Materials Science Forum Vol. 953

Abstract: The modified calcium oxide partially stabilized zirconia ceramics were fabricated using ZrO₂ powder as raw materials, CaO as stabilizer, and nanometre zirconia as modification agent. The relationship between additive amount of nanometre zirconia and the performance of Ca-PSZ ceramics were researched via testing the physical properties, analyzing mineral phase composition, and observing microstructure of the samples. The results show that the introduction of nanometre zirconia powder has a significant effect on the physical properties of Ca-PSZ, with an addition of 8wt%, bulk density was up to 5.08 g/cm³, and the compressive strength reached 381 MPa. Compared with the unmodified Ca-PSZ sample, the porosity of the modified Ca-PSZ samples decreased by 40%, and the compressive strength increased by 70%. The introduction of nanometre zirconia has an inhibitory effect on the abnormal growth of zirconia grains and improves the densification of the Ca-PSZ ceramics. Through the formation of intragranular structure, nanometre zirconia can induce transgranular fracture and weaken crystalline fracture, thereby increasing the strength of the Ca-PSZ ceramics.

Abstract: A finite element model on the single fiber pull-out test of short fiber reinforced rubber matrix sealing composites (SFRC) were established. The effects of the interphase properties on the interfacial stress distribution and initial debonding strain are investigated based on the cohesive zone model (CZM). The influences of interphase thicknesses and elastic modulus on the interfacial debonding behavior of SFRC are obtained. The results show that the interfacial initial debonding strain increases with the increasement of interphase thickness, and it decreases with the increasement of interphase elastic modulus. An interphase thickness of 0.4 μm and an interphase elastic modulus of about 750 MPa are optimal to restrain the initiation of the interfacial debonding.

Abstract: During the curing cycle, the residual stress has influence on cure-induced deformation for carbon fiber reinforced plastics (CFRP) laminates, which is highly susceptible to the ply design. Therefore, the change laws of strain and the effect of residual stress in CFRP laminates after curing, which is of great significance to ply design, were cleared by using the combining pattern of thermocouple and fibre Bragg grating (FBG) sensors. For the FBG sensors embedded with different directions in lay-up CFRP laminates, the temperature and strain in different directions of composite laminates were obtained in real-time. Monitoring results show that compared with strain in 45° direction, the carbon fibers (CF) act stronger to inhibit strain in 0° direction and weaker to inhibit strain in 90° direction of resin. After curing, the residual strain in 0° direction is tensile strain, and the residual strain in 45° direction and 90° direction are compressive strain. Meanwhile the value of residual strain in 90° direction is greater than that in 45° direction.

Abstract: The uncontrollable forming quality of component caused by the uncontrollable expansion pressure of silicon rubber mandrel has long been an unsolved problem in the fabrication of composite hat-shaped components. Here,we advanced a novel mandrel pressurization method combining silicon rubber mandrel and inflatable mold. Cure experiments were carried out based on the combined mandrel with different adjustable apertures. At the same time, the resin pressure of the components was monitored on-line during the curing process by using a self-built pressure on-line monitoring system, and their geometric accuracies and forming quality were evaluated. The experimental results show that the combined mandrel forming method can control the uniformity of pressure, geometric accuracies and forming quality of the hat-shaped component effectively, and the optimal size range is obtained with the hole ratio of 0.4~0.53. Compared with the traditional auxiliary forming method, combined mandrel pressurization method greatly reduces the requirements on the size of the mandrel structure and broadens the process window of the mandrel for the curing of hat-shaped component.

Abstract: Due to the rapid scientific and technological developments in the aerospace industry, the requirement for safety and energy absorption efficiency is increasing, and in order to achieve that target, the analyzing of the sudden crash is required to know how to reduce it. Therefore, the main objective of the present work is to analyze the crashing response of the hybrid composite fuselage structure during different impact landing conditions. Moreover, extract the maximum acceleration at the most important locations in the UAV fuselage where most of the critical system is installed. The explicit non-linear finite element software LS-DYNA/WORKBENCH ANSYS is chosen to simulate the crushing of the referenced and the proposed UAV fuselage and investigate the maximum crushing accelerations responses on the payload under different landing conditions. The numerical results show that strengthen the fuselage structure using hybrid composite material has a notable effect on the energy absorption, and transferred acceleration on the payload. Moreover, the hybrid composite fuselage structure can reduce the transferred acceleration on the payload up to 39.65% in comparison with the metal fuselage. In addition, to study the crash analysis during sudden accidents is very important, in order to find the way to reduce it, but can’t avoid it. Hence, the UAV payload should be arranged to avoid the maximum acceleration.

Abstract: In this paper a comparison between the results of the stress analysis of wing spar of metallic and composite materials has been done in order to assess how the use of composites modifies the weight and strength of the structure. To perform this assessment, the Ansys tutorial program was used to check our results for metallic and composite materials. This test was made for different arrangements of composite material to reach the best design of the composite spar to use it in manufacturing airplanes. There is a large amount of analysis and validation performed at the certification to demonstrate the Airworthiness requirements of aircraft structure so that, the composites have been subject of permanent interest of various specialists at the previous years. This secures the safe operation of the airplane under standard operating environments and also load conditions that the aircraft is intended to operate through its design service life. It is a trial to prove that the composites have a lot of advantages in the manufacturing process.

Abstract: In this paper, a direct co-precipitation method was used to prepare antimony-doped calcium fluoride nanopowders (NPs). The effects of reaction concentration, reaction medium and lanthanum doping on the properties of calcium fluoride NPs were investigated via a control variable method and the best preparation conditions was identified. The structural analysis of the powder materials prepared in this work were carried out by XRD, SEM, ICP and other test methods. By analyzing the experimental data, we found that the best performance of Eu-doped CaF₂ NPs can be acquired under the reaction concentration of 1 mol/L in aqueous solution. In the same time, the NPs possess a high degree of dispersion with an average diameter of 22 nm, which is beneficial to the preparation of transparent Eu³⁺: CaF₂ ceramics with excellent up-conversion luminescence. The results show that the grain size, the crystallinity of the NPs and the amount of Eu infiltration have a decreasing tendency with the increasing reaction concentration, while the degree of agglomeration of the NPs can be enhanced by increasing the reaction concentration.

Abstract: Based on the laboratory micro-motion contact resistance test system, fretting characteristics of the two contact pairs of gold-plated probe and tin-plated samples, gold-plated samples and tin-plated probe, is carried out at different plating thickness, contact force and temperatures. The contact pairs after the fretting experiment were subjected to temperature and humidity test and salt spray test to analyze its environmental reliability. 0.76μmAu-Sn has better fretting characteristics than 4μm Sn-Au. When the contact force is greater than or equal to 100 gf, the two kinds of contact pair exhibit good fretting characteristics. Thickness of sample plating is more important than that of probe. The influence of ambient temperature on fretting contact performance is the weakest. The increase of contact resistance of contact pair 4μm Sn-Au is higher than that of 0.76μmAu-Sn after accelerated environmental simulation experiments.

Abstract: High energy density and rechargeable lithium ion batteries are attracting widely interest in renewable energy fields. The preparation of the high performance materials for electrodes has been regarded as the most challenging and innovative aspect. By utilizing a facile combustion synthesis method, pure nanostructure LiNi_0.5Mn_1.5O₄ cathode material for lithium ion batteries were successfully fabricated. The crystal phase of the samples were characterized by X-Ray Diffraction, and micro-morphology as well as electrochemistry properties were also evaluated using FE-SEM, electrochemical charge-discharge test. The result shows the fabricated LiNi_0.5Mn_1.5O₄ cathode materials had outstanding crystallinity and near-spherical morphologies. That obtained LiNi_0.5Mn_1.5O₄ samples delivered an initial discharge capacity of 137.2 mAhg^-1 at the 0.1 C together with excellent cycling stability and rate capability as positive electrodes in a lithium cell. The superior electrochemical performance of the as-prepared samples are owing to nanostructure particles possessing the shorter diffusion path for Li⁺ transport, and the nanostructure lead to large contact area to effectively improve the charge/discharge properties and the rate property. It is demonstrated that the as-prepared nanostructure LiNi_0.5Mn_1.5O₄ samples have potential as cathode materials of lithium-ion battery for future new energy vehicles.

Abstract: In this paper, the effects of the quantum yield of free radicals in cryptochrome exposed to different electromagnetic fields were studied through the quantum biology. The results showed that the spikes characteristics was produced in the free radicals in cryptochrome, when it exposed to the applied magnetic field (ω = 50 Hz, B₀ = 50 μT). The spikes produced by the electromagnetic field was independent of the changes of polar θ. When the frequency of the magnetic field increased, the spikes characteristics produced in unit time also increased. These results showed that the environmental electromagnetic field could affect the response of organisms to the geomagnetic field by influencing the quantum yield in the mechanism of free radical pair.It provided a basis for studying the influence of environmental electromagnetic field on biology, especially the navigation of biological magnetism.