An Experimental and Computational Study of the High-Velocity Impact of Low-Density Aluminum Foam

The study presents the results of an experimental and computational study of the high-velocity impact of low-density aluminum foam into a rigid wall. It is shown that the aluminum foam samples deformed before hitting the rigid wall because of the high inertial forces during the acceleration. During the impact, the samples deformed only in the region contacting the rigid wall due to the high impact velocity; the inertial effects dominated the deformation process. However, the engineering stress–strain relationship retains its typical plateau shape until the densification strain. The experimental tests were successfully reproduced with parametric computer simulations using the LS-DYNA explicit finite element code. A unique computational lattice-type model was used, which can reproduce the randomness of the irregular, open-cell structure of aluminum foams. Parametric computer simulations of twenty different aluminum foam sample models with randomly generated irregular lattice structures were carried out at different acceleration levels to obtain representative statistical results. The high strain-rate sensitivity of low-density aluminum foam was also observed. A comparison of experimental and computational results during aluminum foam sample impact shows very similar deformation behavior. The computational model correctly represents the real impact conditions of low-density aluminum foam and can be recommended for use in similar high-velocity impact investigations.

Superconducting YBCO Foams as Trapped Field Magnets

Superconducting foams of YBa 2 Cu 3 O y (YBCO) are proposed as trapped field magnets or supermagnets. The foams with an open-porous structure are light-weight, mechanically strong and can be prepared in large sample sizes. The trapped field distributions were measured using a scanning Hall probe on various sides of an YBCO foam sample after field-cooling in a magnetic field of 0.5 T produced by a square Nd-Fe-B permanent magnet. The maximum trapped field (TF) measured is about 400 G (77 K) at the bottom of the sample. Several details of the TF distribution, the current flow and possible applicatons of such superconducting foam samples in space applications, e.g., as active elements in flux-pinning docking interfaces (FPDI) or as portable strong magnets to collect debris in space, are outlined.

Superconducting YBCO Foams as Trapped Field Magnets

Superconducting foams of YBa$_2$Cu$_3$O$_y$ (YBCO) are proposed as trapped field magnets or supermagnets. The foams with an open-porous structure are light-weight, mechanically strong and can be prepared in large sample sizes. The trapped field distributions were measured using a scanning Hall probe on various sides of an YBCO foam sample after field-cooling in a magnetic field of 0.5 T produced by a square Nd-Fe-B permanent magnet. The maximum trapped field (TF) measured is about 400 G (77 K) at the bottom of the sample. Several details of the TF distribution, the current flow and possible applicatons of such superconducting foam samples in space applications, e.g., as active elements in flux-pinning docking interfaces (FPDI) or as portable strong magnets to collect debris in space, are outlined.

Microspheres as potential fillers in composite polymeric materials

Microspheres used in our work were acquired from one of Kazakhstan coal-fueled power plant. The size of the microspheres varied between 45 and 400 μm, the median particle size (D50) was 158 μm. Microscopic analysis revealed that the material consisted mainly of cenospheres. The results of elemental and oxide analysis showed that microspheres were composed of aluminosilicates. Identified crystalline phases were mullite (approx. 12 %) and trace amount of quartz (silica). Microscopic observations of the cross-sectional surface of both unmodified PUR foam and foams modified with microspheres showed a well formed, cellular structure of all materials. The observed cells are polyhedron in shape, most of them are closed, microspheres were uniformly distributed within polymer matrix and placed between cells. The apparent densities calculations of the samples showed that when microspheres were added to the polymer matrix, apparent density of the resulting composite materials increased. The results of elemental analysis pointed out the highest content of all three elements in unmodified PUR foam sample. The addition of the microspheres to the system resulted in decrease of the concentration of all three elements.

New Approach for Fabrication of Auxetic Foam and Determination of Poisson's Ratio

Conventional foam could be converted to auxetic foam under auxeticity process. A new and simple technique to fabricate auxetic foam and to further determine its Poisson’s ratio is described in this paper. It is evident that the present modified technique in fabricating auxetic foam could be adopted to produce desirable auxeticity characteristics. Moreover, the approach used for determination of Poisson’s ratio has considerably merit with great cost effectiveness. This method is, however, specific to auxetic foam sample under compression loading.

Fabrication of Stainless Steel Foams Using Polymeric Sponge Impregnation Technology

316L stainless steel foams (SSFs) are fabricated successfully by polymeric sponge impregnation technology. The effects of mass fractions of PVA and powder on LOAD in impregnated sponge samples are investigated, and the effects of sintering temperature on apparent density, open porosity and bending strength of SSFs samples are also discussed. The experimental results show that the impregnated sponge samples may hold excellent 3D open-cell network structure and uniform muscles when the mass fractions of PVA and powder in slurry are kept in 9-13 % and 52-75% respectively; with rising the sintering temperature, the apparent density and bending strength of SSFs gradually increases, the open porosity reduces. After the temperature exceeds 1260°C, the bending strength reduces oppositely. A stainless steel foam sample with open porosity of 81.4% and bending strength of about 56.8 Mpa can be obtained after sintering at 1260 °Cfor 30min.