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This work evaluated the fracture toughness of the low-temperature carbonized elastomer-based composites filled with shungite and short carbon fibers. The effects of the carbonization temperature and filler content on the critical stress intensity factor (K1c) were examined. The K1c parameter was obtained using three-point bending tests for specimens with different l/b ratio (notch depth to sample thickness) ranging from 0.2 to 0.4. Reliable detection of the initiation and propagation of cracks was achieved using an acoustic sensor was attached to the samples during the bending test. The critical stress intensity factor was found to decrease linearly with increasing carbonization temperature. As the temperature increased from 280 to 380 °C, the K1c parameter was drastically reduced from about 5 to 1 MPa·m1/2 and was associated with intense outgassing during the carbonization step that resulted in sample porosity. The carbon fiber addition led to some incremental toughening; however, it reduced the statistical dispersion of the K1c values.

This paper describes the manufacturing process and properties of single-polymer composites based on ultra-high molecular weight polyethylene fibers produced by hot compaction. The hot compaction results in partial surface melting of the initial fibers, and melted part after cooling forms a matrix of the self-reinforced composites. Using high pressure during hot compaction allows to increase the fibers’ melting point and allows to avoid relaxation processes. Moreover, the fiber-to-matrix ratio may be changed using this approach by varying pressure and temperature. The flexural test was carried out to determine the mechanical properties. Samples obtained at 160 °C and 50 MPa have optimum properties (flexural strength and Young’s modulus were equal to 116.5 MPa and 15.3 GPa, respectively). It was found that mechanical properties of the obtained composites depend on both matrix amount and preservation of oriented fibers structure. The small amount of melted fibers does not allow to form matrix for load transferring. But the excessive melting of the fibers can result in a significant decrease in the fibers’ mechanical properties.

Phantoms are widely used substitutes for various types of soft tissues with mechanically and anatomically matching properties. They can be used as advanced tools for training before the surgical manipulation on human organs such as the brain or liver as part of complex operation planning and preparation. We report 3D printing fabrication and characterization of hydrogel composites based on the combination of two biocompatible materials, namely, polyvinyl alcohol (PVA) and phytagel (PHY). The hydrogels were used for the fabrication of brain phantoms in a multistage procedure based around 3D printing. The main goal of this study is to demonstrate the simple, low cost and relatively fast procedure for the creation of hydrogel organ phantoms of high anatomical and mechanical fidelity made from commonly available materials. To this end, three different types of samples were produced to illustrate the flexibility of hydrogel-based 3D printing approach in mimicking the mechanical properties of human organs: brain, lung, and liver soft tissues. The mechanical response was studied using Deben MicroTest 1 kN mechanical testing device and Q800 Dynamic Mechanical Analyser in compression mode. The results reveal close matching of the dynamic non-linear mechanical response of the phantoms to those of the corresponding natural soft tissues.

This review presents the results of the local formation of nanostructured porous silicon (NPSi) on the surface of silicon wafers by anodic etching using a durite intermediate ring. The morphological and crystallographic features of NPSi structures formed on n- and p-type silicon with low and relatively high resistivity have also been investigated. The proposed scheme allows one to experiment with biological objects (for example, stem cells, neurons, and other objects) in a locally formed porous structure located in close proximity to the electronic periphery of sensor devices on a silicon wafer.

The effect of thermal treatment of glass fibers (GF) on the mechanical and thermo-mechanical properties of polysulfone (PSU) based composites reinforced with GF was investigated. Flexural and shear tests were used to study the composites&rsquo, mechanical properties. A dynamic mechanical analysis (DMA) and a heat deflection temperature (HDT) test were used to study the thermo-mechanical properties of composites. The chemical structure of the composites was studied using IR-spectroscopy, and scanning electron microscopy (SEM) was used to illustrate the microstructure of the fracture surface. Three fiber to polymer ratios of initial and preheated GF composites (50/50, 60/40, 70/30 (wt.%)) were studied. The results showed that the mechanical and thermo-mechanical properties improved with an increase in the fiber to polymer ratio. The interfacial adhesion in the preheated composites enhanced as a result of removing the sizing coating during the thermal treatment of GF, which improved the properties of the preheated composites compared with the composites reinforced with initial untreated fibers. The SEM images showed a good distribution of the polymer on the GF surface in the preheated GF composites.

Ultra-high molecular weight polyethylene-based self-reinforced composite materials were studied. Surface of the ultra-high molecular weight polyethylene fibers was modified by direct fluorination and nitric acid treatment. Structure and mechanical properties of self-reinforced ultra-high molecular weight polyethylene depending on the content and type of modified fibers were studied. It was shown that self-reinforcing of ultra-high molecular weight polyethylene allows to obtain materials with improved strength–elastic properties. Tensile strength and Young’s modulus of the self-reinforced composite materials are more than three times higher than that of the unfilled ultra-high molecular weight polyethylene.

Ultra-high molecular weight polyethylene (UHMWPE) is a bioinert polymer that is widely used as bulk material in reconstructive surgery for structural replacements of bone and cartilage. Porous UHMWPE can be used for trabecular bone tissue replacement, and it can be used in living cell studies as bioinert 3D substrate permeable to physiological fluids. It is important to develop techniques to govern the morphology of open-cell porous UHMWPE structures (pore size, shape, and connectivity), since this allows control over proliferation and differentiation in living cell populations. We report experimental results on the mechanical behavior of porous open-cell UHMWPE obtained through sacrificial removal (desalination) of hot-molded UHMWPE-NaCl powder mixtures with pore sizes in the range 75 &micro, m to 500 &micro, m. The structures were characterized using SEM and mechanically tested under static compression and dynamic mechanical analysis (DMA), bending, and tensile tests. Apparent elastic modulus and complex modulus were in the range of 1.2 to 2.5 MPa showing a weak dependence on cell size. Densification under compression caused the apparent elastic modulus to increase to 130 MPa.

The paper studies new high-temperature thermoplastic impregnated unidirectional carbon fiber composites. The research focuses on the effect of thermal and chemical oxidation of the carbon fibers surface on the interfacial interaction between fibers and polysulfone and polyphenylene sulfide as well as thermal and mechanical properties of the composites. The research reveals the interaction between carbon fibers and the polymer matrix depend both on the type of surface treatment and nature of the polymer. The chemical oxidation of carbon fibers results in good interfacial interaction, and the best mechanical properties were observed for tows impregnated with polyphenylene sulfide.

Barium hexaferrite powder samples with grains in the μm-range were obtained from solid-state sintering, and crystals with sizes up to 5 mm grown from PbO, Na2CO3, and BaB2O4 fluxes, respectively. Carbonate and borate fluxes provide the largest and structurally best crystals at significantly lower growth temperatures of 1533 K compared to flux-free synthesis (1623 K). The maximum synthesis temperature can be further reduced by the application of PbO-containing fluxes (down to 1223 K upon use of 80 at % PbO), however, Pb-substituted crystals Ba1–xPbxFe12O19 with Pb contents in the range of 0.23(2) ≤ x ≤ 0.80(2) form, depending on growth temperature and flux PbO content. The degree of Pb-substitution has only a minor influence on unit cell and magnetic parameters, although the values for Curie temperature, saturation magnetization, as well as the coercivity of these samples are significantly reduced in comparison with those from samples obtained from the other fluxes. Due to the lowest level of impurities, the samples from carbonate flux show superior quality compared to materials obtained using other methods.