Polyurethanes are widely used in different industries, as insulators, coating or adhesive agents. Several of their medical applications include various implants, artificial heart valves, surgical instruments or catheters. The versatility and biocompatibility of these polymer products lead to their application as drug or genetic material delivery systems. We aim to evaluate different parameters that affect the encapsulation efficiency of polyurethanes, using a computational approach, in order to improve the transmembrane transfer and the bioavailability of an active agent loaded inside a drug delivery system. 2D structures of different etheric- and esteric-PU macromolecular chains were modeled in ChemBioDraw, while molecular structures of the three active agents (Deoxyribonucleic acid, Guanidine,1`-[(methylethanediylidene)dinitrilo]di-, mixt. with Calf Thymus DNA, and 2`-Deoxycytidine-5`-phosphonic acid) were imported from PubChem database. Open software such as Open Babel and PyRx were used to convert files and to analyze the binding affinity based on the predicted dissociation constants. Structural parameters of the tested compounds were calculated in HyperChem 8.0. The polymer chains showed very large values for van der Waals potentials, refractivity and polarizability compared to the active agents. Even if there were no major differences in terms of binding affinities between the tested assemblies, the best orientation ligand-macromolecule was the 2`-Deoxycytidine-5`-phosphonic acid encapsulated inside LDI and PEG-based polyurethane carrier. On the other hand, the values of Root Mean Square Deviation have identified that the best geometric fit to be the Deoxyribonucleic acid encapsulated inside IPDI and PCL-based polyurethane macromolecule. The assemblies between genetic materials and polyurethane drug delivery systems are not experimentally known and this study could orientate towards new potential therapies. These results indicate that there is no significant change in the values of the docking parameters with different PU synthesis precursors; however, a good compatibility between LDI and PEG-based chain and 2`-Deoxycytidine-5`-phosphonic acid was identified. Further studies are needed to evaluate the in vitro and in vivo utility of this finding.
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This paper presents preliminary results and discussion on two aramid fabrics in order to establish their stab resistance when used as panels with different numbers of layers. Twaron fabrics SRM509 and CT736CMP, were arranged in 16 and 20 layers and in a combination of them (10 layers SRM509 and 10 layers CT736CMP). Samples of 130 mm x 130 mm were cut from the fabrics, weighed and measured for thickness. All tests were done for an impact energy of 24 J (the resulting impact velocity being 3 m/s). The blade had the geometry recommended in the standard Stab Resistance of Personal Body Armor NIJ Standard–0115.00 as P1. The conclusion of this analysis is that the better behavior to stab is obtained for panels that have higher gradients in time, for all four characteristics here discussed: force, displacement, absorbed energy and velocity. When using hybrid panels, the results could intermediate those of the components, this solution could be recommended for reasons as price, weight.
The torus or toroidal surfaces are geometries that can be easily found in various industrial applications, from containers, devices, cartwheels, design objects and even machine parts, being also a geometric primitive often used in solid constructive geometry. For a better understanding of the torus–type surface mechanical behavior, this paper aims to study the toroidal geometry manufactured from ABS material by using the FDM 3D printing method and subjecting each sample to compression tests to identify the influence of the sample filling percentage in the case of triangular pattern.
In this study, Ethylene-vinyl acetate (EVA) based composites filament, with four different volume fraction of the nano-sized carbon black particles (NCB) were produced by melt mixing using a single extruder. The morphology of the EVA/NCB was studied using SEM, where a 3-D network of the NCB was presented. Thermal gravity analysis (TGA) measurement was utilized, denoting the degradation temperature of EVA, and presetting the actual volume fraction of NCB in the composites. Mechanical properties, e.g. elongation at break, tensile strength of the EVA/NCB filament was studied. Most importantly, the strain sensoring behavior of the EVA/NCB was investigated ultilizing a tensile testing machine coupled with a pico-ammeter. The gauge factor for various strain range, as well as the relative change of the resistance during the cyclic measurement of the NCB/EVA composites was calculated. Moreover, the measured data were fitted using some mathematical modellings, which reveals the potential of the strain sensoring behavior of the NCB/EVA composites in this study. Overall, this study introduces a durable NCB/EVA composites using as strain sensor oriented to industrial large-scale production, and the proposed modelling provides an effective evaluation method on its strain sensoring behavior.
In this study, a selective flexible flow path system was developed so that two types (4 cavities) of different shapes, sizes, and weights could be produced simultaneously or individually according for a production plan.The selective flexible flow path system is a method of exchanging sprue parts manufactured in a branched or one-way direction. This method reduces mold costs and provides production flexibility because only the desired cavities can be filled with resin in a multi-cavity mold. Since parts with different shapes and weights are produced simultaneously or separately, it is most important to maintain a uniform filling balance between each cavity. To optimize of filling balance, the optimum value of control factors was derived using the Taguchi technique (DOE) to improve the filling balance. In addition, molds were manufactured under the optimal conditions after checking the filling balance through a CAE analysis. As a result, the flow balance ratio of each product was confirmed to be within 0.6%, and the precision of the product was guaranteed to be within 1%. In this study, it was confirmed once again that the improvement of the filling balance of the family mold had a great influence on the production.
The paper generalizes the Timoshenko model for thick bars, using a new model that is applied to the vibration study of multilayer composite bars. In the proposed mathematical model, three coefficients are introduced that take into account the non-uniformities of the tangential and normal stresses in the bar section. The vibrations of some composite bars with a polypropylene honeycomb core with a thickness of 10 mm, 15 mm and 20 mm are experimentally studied, on the faces of which one or two layers of carbon fiber, respectively glass fiber was poured. For each analysed bar, the stiffness and the equivalent modulus of elasticity are determined and the variation of the damping coefficient according to the length of the bar is studied.
The paper presents the results obtained after the tribology of composite materials with organic components intended for the manufacturing of brake shoes for motor and towed rolling stock. We analyzed the tribological behaviour of the samples of experimental composite material in comparison to the phosphorous cast iron frequently used for manufacturing brake shoes.
The purpose of experiment was the highlight of the creep of ring from polyethylene pipe subjected to internal pressure. To create the internal pressure in the HDPE pipe ring, a weight of 4.5 kg was superimposed on it, in the form of a cylindrical plate. In order to evaluate the strains of the elastic element subjected to the tensile stress, respectively compression, tensometric marks 1 and 2 are placed on the outside, in the case of the circular section. The internal pressure test was performed to evaluate the strains of the material of a PE 100 polyethylene ring in two directions: one axial (longitudinal) and the other transverse (circumferential) in order to highlight the creep of the pipe material due to its structure. In a polyethylene pipe stressed at internal pressure, due to the symmetry the tangential stresses are zero. The axial strain initially showed a positive increase, followed by a decrease, reaching negative values towards the end of the experiment, while the circumferential strain recorded positive values, about 300 times higher than the initial ones. The principal stress changed approximately linearly. The circumferential stress recorded the maximum value of σ1=0.33 MPa (3.3 bar) after two and a half hours of experiment. Based on such this test could be calculate Poisson`s ratio ν.
The use of fiber-reinforced polymer (FRP) composites in compressive members is advantageous to reinforced concrete structures in order to alleviate the problem of corrosion of steel reinforcement and to produce a lightweight and efficient structural element. This investigation aims to propose the theoretical models for capturing the axial loading capacity (ALC) of hollow concrete columns (HCCs) having main FRP rebars and transverse FRP spirals. All the glass-FRP-reinforced HCCs portray two-peak load performance. The first peak is due to the gross cross-sectional area of concrete while the second peak is due to the core material laterally wrapped with FRP spirals. For the prediction of the first peak load of HCCs which is equal to the maximum capacity of solid concrete columns, a database of 279 FRP-reinforced columns was produced from the previous research and the ALC models were suggested; one for capturing the first peak and the other for estimating the second peak ALC of HCCs. The predictions of proposed models were compared with the test results from the literature. A close relationship was perceived between the theoretical and experimental results.
As part of this work, research was carried out on the effect of the addition of expanded perlite (PR) on the mechanical and thermomechanical properties of high-density polyethylene (PE) composites. Composites containing from 1 to 10 wt% of the inorganic filler were produced. Polyethylene-based composites manufactured by twin-screw extrusion and formed in the compression molding process were subjected to mechanical, thermomechanical, and structural analyses. The structure of polymer composites and filler was analyzed using scanning electron microscopy (SEM). It has been correlated with the static tensile tests and results of dynamic thermomechanical analysis (DMA). As part of the work, several thermomechanical parameters were calculated, and the obtained results were discussed with the evaluation of interfacial adhesion based on microscopic analysis. The research showed that despite introducing a 10 wt% of particle-shaped filler, the composites show increased stiffness without noticeable deterioration in tensile strength, simultaneously reducing toughness and brittleness. The analysis of the thermomechanical properties showed the lack of significant effects of the filler influence on the polymer matrix.