Электромагнитный и тепловой анализ электрических машин из композитных материалов

Plant fiber-reinforced polylactic acid (PLA) exhibits excellent mechanical properties and environmental friendliness and, therefore, has a wide range of applications. This study investigated the mechanical properties of three short plant fiber-reinforced PLA composites (flax, jute, and ramie) using mechanical testing and material characterization techniques (SEM, FTIR, and DSC). Additionally, we propose a methodology for predicting the mechanical properties of high-content short plant fiber-reinforced composite materials. Results indicate that flax fibers provide the optimal reinforcement effect due to differences in fiber composition and microstructure. Surface pretreatment of the fibers using alkali and silane coupling agents increases the fiber-matrix interface contact area, improves interface performance, and effectively enhances the mechanical properties of the composite. The mechanical properties of the composites increase with increasing fiber content, reaching the highest value at 40%, which is 38.79% higher than pure PLA. However, further increases in content lead to fiber agglomeration and decreased composite properties. When the content is relatively low (10%), the mechanical properties are degraded because of internal defects in the material, which is 40.42% lower than pure PLA. Through Micro-CT technology, the fiber was reconstructed, and it was found that the fiber was distributed mainly along the direction of injection molding, and the twin-screw process changes the shape and length of the fiber. By introducing the fiber agglomeration factor function and correcting the Halpin-Tsai criterion, the mechanical properties of composite materials with different contents were successfully predicted. Considering the complex stress state of composite materials in actual service processes, a numerical simulation method was established based on transversely isotropic material using the finite element method combined with theoretical analysis. The mechanical properties of high-content short plant fiber-reinforced composite materials were successfully predicted, and the simulation results showed strong agreement with the experimental results.

The mechanical properties of a composite material with a matrix of aluminum alloy D16 reinforced with dispersed silicon carbide particles have been studied. The physicomechanical properties (density, elastic modulus, ultimate tensile strength, and limiting strains) of the composite material with various filler contents are determined experimentally. The experimental results are compared to the results of a theoretical simulation obtained using elastic and elastoplastic models of the composite material. The experimental and the calculated mechanical properties of the composite material with the volume content of the filler up to 30% agree well with each other.

The effects of chemical structure of the resin, reinforcement types, material thickness, and post-cure treatment on the mechanical properties of composite material were examined in this study. Composite materials were produced by combining chopped, woven, and felt glass fibers with thermoset plastic-based matrixes. Orthophtalic polyester (polives 701) and bisphenol-A epoxy vinyl ester (polives3401) resins were chopped in combination with a catalyst system composed of MEK-PEROKSIT and cobalt, and were reinforced with chopped, woven, and felt glass fiber. Composite materials were prepared using a hand lay-up method. Half of the prepared composite materials were post-cured, the other half remained non-treated. A total of 75 tests were performed. Tensile, bending, impact, and hardness tests were performed to determine the mechanical properties of the samples. The test results indicated that durable and strong tractor bonnets can be produced using vinyl ester-based matrix material and 90° glass fiber woven reinforcement material, producing two-layered composite material and curing at 50°C, 80°C, and 110° C.

Some mechanical properties of composite material based on scrap tyres and polyurethane type polymer binder were investigated to underline the significance of binder reactivity on selected mechanical properties of the composite material. Compressive stress and compressive modulus of elasticity E at 10% deformation and Shore C hardness were investigated. Connection was observed between the above-mentioned selected mechanical properties of composite material and reactivity of the polymer binder. It was confirmed previously that the crosslinking degree of polyurethane type binder separately and therefore at the same time mechanical properties of binder were strongly connected with water as a significant factor during the hardening of the polymer. The special objective of this work is to investigate connection between selected mechanical properties of the composite material, content and reactivity of the polymer binder under invariable composite material moulding and hardening conditions.

Purpose This paper aims to perform theoretical and experimental analysis to modify the mechanical properties of the composite materials reinforced with powders and short fibers using different volume fractions and resins. Design/methodology/approach The experimental work involved manufacturing composite laminates and testing the prepared samples under tension to obtain their mechanical properties. The theoretical work involves the calculation of the modulus of elasticity for comparison purposes. This work estimated the modulus of elasticity for short fibers (glass, carbon high-strength, boron) as reinforcements and its properties are evaluated. They were used as powders and discontinuous fibers with different resins, epoxy, polyester, nylon and polyester (PL) matrices. As a result of their balance between performance, cost and processing advantages, short fibers are an effective reinforcement for composite materials, particularly in applications where performance is required but cost or processing constraints are present. Among their key advantages are improved mechanical properties, easy manufacturing techniques, strength, damping capacity, toughness and design flexibility. Findings The results demonstrated a strong agreement between the experimental and theoretical findings, with a maximum difference of no more than 11.6%. The mechanical properties showed that the powder types have an insignificant effect on the mechanical properties of composite materials while the reinforcement types have shown a significant effect. Practical implications The benefits that fiber matrix composites offer in terms of performance, affordability and structural efficiency are driving their expanding use in aerospace, marine and many other industries. Originality/value The results demonstrated that short fiber reinforcement significantly enhanced the composite’s modulus of elasticity and strength by over 50%. The type of short fibers used had a greater impact on these improvements compared to other types of reinforcement fibers.

Balloon catheters are a common tool used in modern microvasive surgery like angioplasty. A problem during balloon dilatation is longitudinal growth, because of the danger of lesions due to shearing forces. Therefore a modified composite material with anisotropic mechanical properties, which rather inflates radially than longitudinally, would be interesting for the application in balloon catheter manufacturing. Multi-walled carbon nanotubes (MWNTs) represent a nanomaterial with a high aspect ratio tubular crystal structure with diameters in the nanometer range and fiber lengths typically in the range of a few microns. They exhibit high elasticity in combination with high mechanical strength and therefore represent an interesting material for the anisotropic reinforcement of polymer-based composite thin films. Therefore we first simulated the micromechanical properties of Polyamide 12-MWNT composite material variants by variation of MWNT concentration and nanofiber alignment with the semi-analytical mean field method. Then in a second step we performed experimental studies, in which we processed commercial Polyamide 12-MWNT composite masterbatch material by extrusion and fabricated tensile test specimens via injection molding and blow film extrusion. The specimens were finally tested in uniaxial tensile tests and the performance of mechanical reinforcement with regard to elastic moduli and yield point was evaluated. Although our results show, that already relative low amounts of MWNTs do have a considerable influence on the mechanical properties of composite materials and anisotropy of blown films, other technological processing strategies than pure melt mixing by extrusion, which may lead to a better interfacial bonding between the carbon nanotubes and the polymer matrix should be considered.

Characterization and Investigation of Mechanical Properties of Composite Materials used for Leaf Spring

Introduction. Dynamic indentation method is considered promising in testing mechanical properties of composite materials. Today, composite materials are widely used in the aviation and aerospace industries. That’s why, testing of mechanical properties of composite materials is so vital.
 Method. To register the current velocity of the indenter penetration into the tested composite material, use is made of a device that enables a contactless measurement of the indenter penetration velocity after the indenter strikes the tested product. 
 The data obtained is digitized and sent to a PC for further processing.
 Results. The experiment produced "contact force – penetration depth" diagrams for three test zones in the prepared samples. The analysis showed that the non-uniformity of mechanical properties in the rod’s butt end and side surface is stipulated by pores and microcracks, and this is confirmed by computer tomography. It is shown that dilaminations, microcracks and local non-uniformity zones in the structure tell on the elasticity modulus measurements.
 Conclusions. The dynamic indentation method allows one to test composites at the micro- and macrostructural level, as well as compute their integral mechanical properties.

Chapter 4 - Micromechanics Models for Mechanical Properties

The present work is to be considered as additional research to the authors' previous studies. It is dedicated to the specification of the significance and impact of certain selected technological parameters on mechanical properties of the composite material based on scrap tires. The special method what is known as the “Greece-Latin square” was applied to estimate significance of each technological parameter (input parameter) for selected properties (output parameters) of the material. Moulding pressure (P), formation time (x), polymer binder content (Cpol.) and the size of rubber particles (R) were selected as the input parameters. Compressive modulus of elasticity (Ec), compressive stress at 10% deformation (σ10%), permanent deformation after 10% deformation in compressive mode (ε) and apparent density (AD) were chosen as the output parameters. An analysis of the obtained dispersion diagrams confirms that composition of the composite material (polymer content) has a greater impact on selected mechanical properties of the material than any other technological input parameter, but apparent density of the composite material demonstrates higher sensitivity to the formation time and moulding pressure of the material than to other input parameters. The obtained results of the experiment enable further optimization of the composite material production technology and at the same time securing the predictable mechanical properties of the material.

Polylactic acid (PLA) material has the potential to be applied in various industrial fields, but this material has shortcomings in terms of mechanical properties, especially mechanical strength, due to brittleness nature of PLA. The manufacture of PLA composite material with the addition of natural fibers as a reinforcing phase is one of the methods to increase the impact strength and maintain the biodegradable properties of the material. However, in theory, there are many factors that affect the mechanical properties of composite materials, thus making the mechanical properties of composites more complex than monolithic materials. The mechanical properties of these composite materials can be predicted using deep learning by paying attention to the relationship between factors, and between factors and their mechanical properties. This relationship has an important role in creating a predictive model with good accuracy. Therefore, correlation analysis is an important thing to do. Correlation analysis was applied using Python programming language to determine the relationship between the impact strength of natural fiber-reinforced PLA biocomposites with its feature information: chemical composition, density, dimensions, surface chemical treatment of natural fibers, matrix-reinforcement volume fraction, and the type of processing used to manufacture the material.

Nanostructured materials gained great importance in the past decade, owing to their wide range of potential applications in many areas, e.g. mechanical, structura l, sensor devices, biomedical, electronics. A large interest is involved with carbon nanotubes, which can be used as a main constituent of composite materials characterized by exceptional mechanical and electrical properties, very suitable for aerospace ap plications, due to their light weight, mechanical strength and flexibility. Recent results obtained in our laboratories are presented, concerning measurements of the electrical and mechanical properties (resilience and Young Modulus, conductivity) of a po lymer matrix, reinforced with carbon nanotubes synthesized by arc discharge and other techniques. Stress and numerical analysis of aerospace structures using carbon nanotubes reinforced composite materials are presented. The evaluation of the reduction wei ght of a typical aerospace structure is discussed.

Electrical and mechanical properties of composite materials based on Carbon Nanotubes are considered for aerospace applications. Nanostructured materials gained great importance in the past decade, owing to their wide ranging potential applications in many areas, e.g. mechanical, structural, sensor, biomedical, electronics. Of particular interest are carbon nanotubes, which can be used as a main constituent of composite materials with exceptional mechanical and electrical properties, very suitable for aerospace applications, also due to their light weight, mechanical strength and flexibility. We present results obtained recently in our laboratories concerning the electrical and mechanical properties (including resilience measurement, stress analysis, conductivity) of carbon nanotubes we synthesized by arc discharge and other techniques, embedded in a polymer matrix.

A critical review on nanotube and nanotube/nanoclay related polymer composite materials

The paper presents investigation results of the heat treatment effect on the properties and corrosion resistance of sintered composite materials with EN AW-Al Cu4Mg1(A) alloy matrix reinforced with Ti(C,N) particles of various volume fractions. Composite materials were examined without heat treatment and after heat treatment which was carried out to improve their properties and corrosion resistance. It was found that the proportion of reinforcement particles Ti(C,N) has an effect on the mechanical properties of composite materials. An increase in hardness and decrease in compression strength, tensile strength and abrasive wear are observed with the increase in the fraction of reinforcement particles. The corrosion susceptibility of the composite materials was determined using the potentiodynamic method in a 3% aqueous solution of NaCl. Based on the determined anode polarisation curves and also on the electrochemical parameters, the investigated materials are susceptible to pitting corrosion.