Jerzy Myalski

Natural Fiber Textile Structures Suitable for Composite Materials

Natural fiber-reinforced composites have drawn attention of the research community mainly because of their economical and environmental attractiveness. So far, the shortened natural fibers were mainly used as the reinforcement, but textile products like yarn and fabrics can improve mechanical properties of composite in a significant way. The objective of the investigation is to develop a textile material suitable for composite reinforcement based on flax fibers. Pure flax fabric as well as hybrid fabrics containing flax fibers and chemical fibers: Kevlar, glass fibers, and poliimid have been developed in order to meet requirements related to mechanical properties of composites. The results of the mechanical tests confirmed suitability of the flax fabrics as a composite reinforcement. Due to strongly hydrophilic properties of pure flax, composites reinforced by the hybrid fabrics with polyaramide or glass fibers showed evidently better mechanical properties (even by about 80%). Chemical modification of flax fabric results in the improvement in adhesion between fibers and matrix. The results obtained within the work show that chemically treated flax fiber can serve as a valuable reinforcement for polymer matrix composite material ensuring mechanical properties comparable to glass fibers.

Producing of Composite Materials with Aluminium Alloy Matrix Containing Solid Lubricants

The paper presents the basics information about manufacturing and selected properties of composite with aluminium alloy matrix containing glassy carbon as a solid lubricant. The so far used method based on mixing the prepared glassy carbon particles with a liquid metal matrix, has been compared with a new method elaborated by the authors of the article. With this novel method carbon is introduced into a composite with the application of liquid carbon precursor and porous ceramic foams. It is then followed by precursor pyrolysis where, as the result, glassy carbon is obtained. Ceramic foams help liquid precursor penetrate the ceramic spheroid pores by forming a thin film of glassy carbon on their walls. The composite produced in such a way features uniform distribution of carbon within its entire volume which significantly improves tribological properties of the composite. Costly mixing procedure is not needed. Sliding friction coefficient of the new composite against cast iron (µ = 0.06-0.28 at wearing in and 0,12 after wearing in) is much lower than in case of composite containing only ceramic foam as a reinforcing phase (μ = 0.25-0.32).

Influence of surface treatment on the wetting process of jute fibres with thermosetting polyester resin

Influence of surface treatment on the wetting process of jute fibres with thermosetting polyester resin The aim of this study is the evaluation of the effect of chemical treatment of jute fibres on their permeability with polyester resin and determination of optimal treatment parameters. Unmodified jute fabric by LENTEX, Poland and polyester resin ESTROMAL 14 were used in the experiments. NaOH and KOH water solutions (various concentration - from 1 to 15% - and treatment duration - from 0.5 to 6h), vinyl acetate, methanol, toluene diizocyanate were used for the treatment. Determination of the effect of the chemical treatment on fiber-resin interaction was made in: infiltration of resin into reinforcement structure tests and fabric absorbability tests. Three criteria: time of penetration of resin into the reinforcing fabric, fabric absorbability and the area of a part of the specimen cross-section penetrated with the resin were taken into account. The fabrics treated with 1-5% - long-time and 15% short-time NaOH and KOH water solutions showed the best results within the tested criteria. These results do not correspondent directly with the mechanical properties of cured composites manufactured on the base of the treated fabrics. Alkali- and organic treatments significantly improve the mechanical performance of natural fibres reinforced composites, but organic treatments (methanol, toluene diisocyanate) gives better improvement in mechanical properties in comparison with the alkali-treatments. The measurement methods applied in the study may be generally useful in the evaluation of the effect of chemical treatment of natural fibres on their wettability with the liquid matrix.

Evaluation of jute fiber preforms absorbability using optical profilographometer

The article presents an analysis of absorbability of polyester resin by jute fabric – untreated and treated in KOH water solutions (various exposure times), toluene diisocyanate, methanol, vinyl acetate and vinylsilane. A change with time in height of a resin droplet put on the fabric specimen was measured using optical profilographometer. The height of droplet was taken as a criterion of absorbability. Additional profilometric scanning observations, scanning electron microscopic observations and a saturation time in vacuum resin infusion tests were conducted in order to confirm and explain the results of the droplet height measurements. Although scanning electron microscopic analysis showed improvement in wetting between the treated fibers and the resin, the droplet height measurements showed that chemical treatment impairs translaminar absorbability of jute fabric. Deterioration of absorbability is caused by swelling of jute strands. However, technological tests showed that in most cases the treatment shortens the saturation time, which testifies an improvement in in-plane absorbability. Especially treatment with vinylsilane and KOH solution visibly shortened the preform impregnation time.

Influence of Al–Al2O3 composite powder on the matrix microstructure in composite casts

Abstract The structural characterization is presented of composite casts with an AlMg4 alloy matrix, with the composite powder (Al–Al2O3)cp reinforcement obtained in a rotary-vibration mill. On the cross-sections of ingots, metallographic specimens have been made and, by means of quantitative metallographic methods, the grain size distributions have been determined. Statistical tests of the results obtained from the grain plane section area measurements have been performed. An influence has been found of the (Al–Al2O3)cp composite powder on the matrix grain size distribution, depending on the distribution of the composite powder particles in the ingot, whereas no influence of (Al–Al2O3)cp on the mean grain size of the AlMg4 alloy has been found.

Effect of Carbon in Fabrication Al-SiC Nanocomposites for Tribological Application

Aluminium-based hybrid composites are a new class of advanced materials with the potential of satisfying the demands in engineering applications. This paper describes the effects of carbon addition on the formation and properties of AMC with SiC nanoparticles reinforcement. The composites were produced via mechanical alloying followed by hot pressing. Three forms of carbon, graphite (GR), multiwalled carbon nanotubes (CNTs), and, for the first time, glassy carbon (GC), were used for the hybrid composites manufacturing and compared with tribological properties of Al-SiC composite without carbon addition. GC and CNTs enhanced formation of Al-SiC composite particles and resulted in a homogeneous distribution of reinforcing particles. On the other hand, GR addition altered mechanochemical alloying and did not lead to a proper distribution of nanoparticulate SiC reinforcement. Hot pressing technique led to the reaction between Al and carbon as well as SiC particles and caused the formation of Al4C3 and γ-Al2O3. The subsistence of carbon particles in the composites altered the predominant wear mechanisms since the wear reduction and the stabilization of the friction coefficient were observed. GC with simultaneous γ-Al2O3 formation in the hybrid Al-SiC(n)-C composites turned out to be the most effective additive in terms of their tribological behaviour.

Effect of Glassy Carbon Particles on Wear Resistance of AZ91E Matrix Composite

In the study the microstructure and tribological behavior of a new magnesium matrix composite reinforced with glassy carbon particles (GCp) were presented. In the composite, obtained by powder sintering, the magnesium alloy AZ91 was applied as a matrix with 20wt% of particles of diameter approx. 100 m. The particle-matrix bonding was characterized by SEM with EDS, TEM with SADP, and nanoidentation tests. The main interest focused on the influence of GCp on the wear behavior of the composite. In the experiment sliding velocities of 0.06, 0.09 and 0.14 m/s, and loads of 2.3, 5 and 9.3 N were applied. The glassy carbon particle microstructure after sliding and the debris were characterized with SEM and EDS. The sliding wear test revealed that glassy carbon particles decreased the coefficient of friction for low load and sliding velocity. The mass lost of composite was very low and no destructive processes of the steel counterface were observed. During the sliding process, a mixture of oxidized AZ91E alloy and dispersed glassy carbon is formed between the composite and the steel counter.

Physical and Mechanical Properties of Composites with Aluminum Alloy Matrix Designed for Metal Forming

The change of matrix and usage of the aluminum alloys designed for the metal forming in making the composite suspension allows to extend the processing possibility of this type of materials. The possibility of the metal forming of the composites obtained by mechanical mixing will extend the range of composite materials usage. Applying of the metal forming e.g. matrix forging, embossing, pressing or rolling, will allow to remove the incoherence of the structure created while casting and removing casting failures. In order to avoid the appearance of the casting failures the homogenization conditions need to be changed. Inserting the particles into the matrix influences on the shortening of the composite solidification. The type of the applied particles influenced the sedimentation process and reinforcement agglomeration in the structure of the composite. Opposite to the composites reinforced with one-phase particles applying the fasess mixture (glassy carbon and silicon carbide) triggered significant limitation in the segregation process while casting solidification. Inserting the particles into the AW-AlCu2SiMn matrix lowers the mechanical properties tension and impact value strength. The most beneficial mechanical properties were gained in case of heterofasess composites reinforced with the particle mixture of SiC and glass carbon. The chemical composition of the matrix material (AW-AlCu2SiMn) allows to increase additionally mechanical characteristics by the precipitation hardening reached through heat casting forming.

Influence of wet chemistry treatment on the mechanical performance of natural fibres

Influence of wet chemistry treatment on the mechanical performance of natural fibres The paper presents determination of the effect of various chemical treatment on the strength of 288 tex jute yarn arisen from the plain weave fabric produced by LENTEX, Poland. The yarn was put to alternative treatments in: NaOH and KOH water solutions with various concentration (from 1 to 15%) and treatment duration (from 0.5 to 6 hours), vinyl acetate, methanol and toluene diisocyanate. After the treatment it was put to tensile tests. Yarn diameter and elementary fibre twist angle were also measured using MICRO PROF FRT optical profilographometer. The SEM micro-photographs have also been performed in order to evaluate the structural changes of the yarn after the treatment. Optimal conditions of alcali-treatment are: 5% concentration and 2h duration for NaOH, 3% concentration and 4h duration for KOH. Such treatments give a growth in yarn rupture force up to 10% and they are well applicable in composite materials manufacturing. Also interaction with vinyl acetate and toluene diisocyanate has practically not negative influence on the mechanical performance of the yarn. Two effects were observed which can explain the influence of chemical treatment on mechanical performance of jute yarn: swelling and change in the orientation of elementary fibres.

Influence of casting procedure on microstructure and properties of Mg alloy–glassy carbon particle composite

Abstract The article presents the microstructure and properties of a new cast composite material with a magnesium alloy matrix (Zn 0.7 wt.%, Zr 0.06 wt.%, Nd 0.41 wt.%, Gd 0.21 wt.% and Mn 0.03 wt.%) and glassy carbon particles (10 wt.%, granulation 70–100 μm), dedicated to a technical application under dry friction conditions, manufactured under industrial conditions from a particle–metal suspension. Microstructural examination revealed that the pressure die casting method eliminates the microvoids formed in the gravity cast process both in the matrix and at the interface and also that it decreases the effect of Zr and other phases accumulating around the particles. The applied procedure of particle extraction from the composites matrix, followed by scanning electron microscopy examination with energy dispersive spectroscopy, revealed the influence of Nd and Gd on the microstructure of the particle–matrix interface. The results of the mechanical and tribological properties tests showed that the application of pressure die casting method for the processing of Mg–GCp composite products improved those properties.