Study on Critical Infiltration Behavior and Law of Liquid Aluminum Alloy in Carbon Fiber Preform

Infiltration effect is an important factor for the preparation of ideal CF/Al composites by liquid infiltration method, so it is necessary to study the infiltration law of aluminum alloy in carbon fiber preform to obtain composite with sufficient and uniform infiltration effect. Through theoretical analysis and calculation of statics and dynamics, critical infiltration pressures of the liquid aluminum alloy in the 2D carbon fiber preform were 0.53 MPa and 3.24 MPa, respectively, when carbon fiber volume fraction was 45 %. Mechanical pressure infiltration method was used to study critical infiltration pressures and behavior of the liquid aluminum alloy in the 2D carbon fiber preform, and the experimental results indicated that the infiltration front of aluminum alloy had never broken through the surface of carbon fiber preform, when the infiltration pressure was 3.5 MPa. Carbon fibers and aluminum alloy were separated and the infiltration effect was not ideal under the pressure of 3.5 MPa. When the infiltration pressure was 7 MPa, the infiltration could be implemented. The actual infiltration pressure of the experiments is greater than the theoretical calculation value, because viscous resistance, solidification resistance and other factors are ignored in the calculation process. However, infiltration depth increases with increase in infiltration time at infiltration pressure of 7 MPa, and this verifies the correctness of the previous theoretical research results.

Study on the Tri-axial Time-Dependent Deformation and Constitutive Model of Glauberite Salt Rock under the Coupled Effects of Compression and Dissolution

Solution mining for glauberite salt rock is a long-term process that takes several years to several decades. Therefore, deposit deformations and subsidence of ground surfaces are time-dependent deformation problems that should consider the effect of water dissolution. In order to investigate the time-dependent deformation characteristics of glauberite salt rock, tri-axial time-dependent deformation tests were conducted under the condition of 4 MPa confining pressure and 5 MPa axial pressure with infiltration pressures of 3, 2, 1, and 0 MPa, respectively, and the micro-CT scan system was used to scan the glauberite specimens before and after the experiment in order to study the fracture evolution inside the specimen, and a damage constitutive model was established to fit the time-dependent deformation curves based on the damage mechanics and effective stress principle. To simulate the solution mining process, the time-dependent deformation process of glauberite salt rock was divided into three stages: hydraulic connection stage, water-saturated stage, and drainage stage. The results demonstrate that the hydraulic connection time for glauberite salt rock decreases with increasing infiltration pressure. The time-dependent deformations of the specimens at the hydraulic connection and saturated-water stages are significantly affected by the effective stress and continual mineral dissolution. At the drainage stage, the softening degree of the solid skeleton mechanical properties, which is caused by the dissolution effect and infiltration pressure loading history, decides the deformation of glauberite salt rock. In addition, the degree of softening inside glauberite salt rock caused by dissolution becomes more severe with increasing infiltration pressure using the micro-CT scan technology. Lastly, the time-dependent damage constitutive model is able to describe the tri-axial time-dependent deformation behavior of glauberite salt rock, and the variations of time-dependent deformation parameters further indicate the damage evolution of the solid skeleton mechanical properties of glauberite caused by infiltration pressure and dissolution effect.

Influence of Infiltration Pressure on the Microstructure and Properties of 2D-CFRP Prepared by the Vacuum Infiltration Hot Pressing Molding Process

The critical infiltration pressures of the matrix in a two-dimensional (2D) carbon fiber preform were calculated theoretically, and the calculated values of the static and dynamic models were 0.115 and 0.478 MPa, respectively. Compared with the dynamic model, there is no viscous resistance or infiltration front gas pressure in the static model, so the static value is obviously lower than the dynamic value. To verify the rationality of theoretical calculation, 2D carbon fiber reinforced plastics (2D-CFRP) with infiltration pressures of 0.5, 0.6, 0.7, 0.8, and 0.9 MPa were prepared by the vacuum infiltration hot pressing molding process. The microstructure of the composite was observed and the bending strength was tested by three-point bending test. The results show that the infiltration pressure has an important influence on the infiltration effect and the bending fracture morphology. When the infiltration pressure is 0.7 MPa, the composite has an excellent infiltration effect. The fibers distribute reasonable in the fracture. Stress can be effectively transferred when the composite material is loaded. And the bending strength of the composite material reaches 627 MPa at this time.

Preparation and Sound Absorption Coefficient Test of Aluminum Foam with CaO Granules Infiltrating Agent

Three kinds of aluminum foam of different pore sizes were prepared with a tailor-made low-pressure infiltration device. CaO granules in three sizes (0.45~0.71mm,0.71~090mm and 1.25~1.60mm) were selected as infiltrating agents. The processing parameters were as follows: granules preheat temperature of 700 °C,infiltration pressure of 0.04 MPa and aluminum liquid temperature of 720 °C. In order to improve the removal performance and porosity, mixture of CaO powder of finer than 300 mesh and pure alcohol was mixed uniformly with granules, which made the slurry-coating granules conformal contacts rather than point contacts as in the traditional infiltration method. The testing results show that among all aluminum foam specimens tested with transfer function methods, two kinds have high sound absorption coefficient in low frequency (250~1600Hz).

Effect of FLiBe Infiltration Pressure on Microstructure of Matrix for TMSR Fuel Elements (FEs)

The matrix graphite of fuel elements (FEs) with infiltration of 2LiF-BeF2(FLiBe) at different pressures varying from 0.4 MPa to 1.0 MPa, has been studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and positron annihilation lifetime (PAL) measurement. The result of XRD reveals that diffraction patterns of FLiBe appear in matrix graphite infiltrated with FLiBe at a pressure of 0.8 MPa and 1.0 MPa. The surface morphology from SEM shows that FLiBe mainly distributes within macro-pores of matrix graphite. PAL measurement indicates that there are mainly two positron lifetime components in all specimens:τ1~0.21 ns and τ2 ­~0.47 ns, ascribed to annihilation of positrons in bulk and trapped-positrons at surface, respectively. The average positron lifetime decreases with infiltration pressure, due to the decrease in annihilation fraction of positrons with surface after infiltration of FLiBe into macro-pores.

A Technology of Composite Reinforced Infiltration

A series of advantages for resin matrix composites make it get extensive application in PCB Field. However, because the properties of composites depend on process crafts badly,unreasonable processing technology will lead forming difficult, and then redesign is needed. This affects production efficiency badly in PCB enterprise. According that composites forming process is huge and complicated, in order to evaluate whether it is rensonable on produce process. This paper try to discuss the technical method of improving the wettability of the composite material from the angle of the production process by increasing the infiltration area, gradually exhaust, increasing the total amount of the base material, pressure infiltration velocity difference and improve the shortcomings in the material production process review. This paper validates the methods useful and practical. It can get a better production effect of infiltration by increasing infiltration area, step by step exhaust, increasing the total matrix materials, speed difference infiltration, pressure type wait for infiltration. The rapid infiltration production technology not only improves the performance of composite materials, but also has important significance to improve the interfacial properties of the composites.

Crushing of circular steel tubes filled with nanoporous-materials-functionalized liquid

The crush behaviors of steel tubes filled with nanoporous-materials-functionalized liquids are experimentally investigated under quasi-static and dynamic conditions. Results show that the nanoporous-materials-functionalized liquid can enhance the load-carrying and the energy absorption capacities of thin-walled tubes, as the buckling mode is affected. The effective buckling stress increases with the infiltration pressure, and the overall compressibility is highly dependent on the nanopore volume. A general rule of designing nanoporous-materials-functionalized liquid-filled tubes is proposed. The interaction between the tube wall and the nanoporous-materials-functionalized liquid is analyzed.

Experimental Investigation on Liquid Infiltration Speed in Liquid Nanofoam

Liquid nanofoam (LN) as a novel material for energy absorption applications exhibits superior properties, including high energy absorption efficiency, ultra-fast energy dissipation, light weight and small size, over existing options. It is a liquid suspension of nanoporous particles, whose nanopore surface is non-wettable to the liquid molecules. Past studies on LN have focused on quasi-static responses, and the actual system performance under dynamic loadings has remained unclear. In this study, the mechanical behavior of two types of LN samples at various strain rates and the liquid flow speed in the nanopores have been experimentally investigated. The quasi-static behavior of LN is rigorously characterized by an Instron 5982 universal tester, from which we find that large amount of energy is dissipated into heat due to the effective excess solid-liquid interfacial tension, and confirm that the energy absorption efficiency of the LN is determined by the liquid infiltration pressure and the total deformability. The dynamic behavior of the LN is investigated by impacting it with a lab-customized drop tower apparatus at intermediate strain rates (around 102 s−1), from which the measured strain-stress curves are highly hysteretic. By comparing with the quasi-static sorption isotherm curve, we show that the liquid infiltration pressure as well as the total deformability of the LN sample in liquid marble form is not affected by the increased strain rate. This suggests that the dynamic behavior of LN can be characterized by quasi-static compressive tests. In the dynamic tests, the ultra-fast energy dissipation rate of LN indicates that the real liquid flow speed in nanopores is much higher than that predicted by the continuum theory. The flow speed can be directly measured from the strain rate by considering the total surface area of the nanoporous particles exposed to the liquid phase. The flow speed is related to the external remote pressure and the 3D porous structure of nanoporous particles. We have examined for the first time the dynamic behaviors of LN, and demonstrated the energy absorption capacity of LN can be activated at desired pressure range by virtue of the strain rate-independent liquid infiltration behavior. This is the first experimental approach to characterize the liquid flow speed in nano-environment. These findings provide strong evidence supporting the potential application of LNs to mitigate energy in blunt impact scenarios such as head to head and head to shoulder collisions in sports, traffic accidents and ballistic impact.

Fabrication of Aluminum-Ceramic Composites with TiC-Ni Skeleton by SHS Pressing Method

One-stage technology of obtaining aluminum-ceramic skeleton composites by combining the processes of self-propagating high-temperature synthesis (SHS) of the porous skeleton and its infiltration under pressure with molten aluminum (method SHS-pressing) was considered. Experimental study of the effect of the pressure of infiltration on the distribution of the content of aluminum over the height and radius of the disk-shaped sample with SHS skeleton made of a cermet of TiC-Ni was performed. Mechanisms of the formation of structure and properties of the composite depending on the infiltration pressure were described.