Jiri Militky

ULTIMATE MECHANICAL PROPERTIES OF BASALT FILAMENTS

Basic characteristics of basalt filaments are described. The main aim of this study is to explore tensile strength distribution based on experimental data. To select the appropriate failure risk function, the maximum likelihood method and methods based on order statistics are used. The use of basalt filaments in sewing thread constructions is also discussed.

Reinforcement of wet milled jute nano/micro particles in polyvinyl alcohol films

Textile industry generate significant amount of waste fibres in form of short lengths during mechanical processing. However these short fibres possess excellent properties suitable for many other applications. The objective of this work was to use them for the preparation of nanoparticles/nanofibres as fillers in biodegradable composite applications such as food packaging, agriculture mulch films, automotive plastics, etc. The present paper concerns with jute fibres as a source of nanocellulose for reinforcement of PVA mulch films. Jute fibres were first refined to micro/nanoscale particles in form of nanofibrillar cellulose (NFC) by high energy planetary ball milling process in dry and wet condition. Wet milling was observed more efficient than dry milling in terms of unimodality of size distribution with reduction in size below 500 nm after milling for 3 hours. Later the obtained particles were used as fillers in Poly vinyl alcohol (PVA) films and their reinforcement evaluated based on thermal properties. It was observed that glass transition temperature (Tg) of PVA films improved from 84.36 °C to 95.22 °C after addition of 5 % jute particles without affecting % crystallinity and melting temperature (Tm) of PVA. Dynamic mechanical analysis of composite films with 5 % jute particles showed higher value of 14×108 Pa for storage modulus in comparison to 9×108 Pa of neat composite film. The percolation effect was observed more above glass transition temperature which consequently resulted in improved transfer of stiffness from jute particles to PVA matrix above 50 °C. The percolation phenomena also explained the improvement in thermal stability by 10 °C for every increased loading of jute particles due to formation of hydrogen bonds with PVA matrix.

Coating of cellulose-TiO2 nanoparticles on cotton fabric for durable photocatalytic self-cleaning and stiffness.

A new route to make cotton fabric self-cleaning and permanently stiff by coating cellulose-TiO2 on its surface is demonstrated herein. Cellulose-TiO2 dispersion was used for coating and was prepared by mixing TiO2 nanoparticles with cellulose in 60% H2SO4 solution. The surface morphology of cellulose-TiO2 nanoparticles coated sample was analyzed by SEM. The appearance of white TiO2 particles on the surface of the cotton fabric confirmed the successful coating process. The Orange II dye was used as stain and its degradation was observed under UV light. X-ray diffraction analysis showed that cellulose II content increases slightly (by 5.3%) after the solvent treatment. Washing fastness study showed that the fabric stiffness was permanent and self-cleaning properties were stable with 1, 3 and 5% TiO2 coated samples. Air and water vapor permeability was not decreased considerably, whereas tensile strength was increased significantly after coating.

Air permeability and light transmission of weaves

The main aim of this contribution is characterization of fabric porosity by the light transmission and comparison of this characteristic with air permeability and idealized geometrical structure of selected weaves. For characterization of air permeability the classical apparatus has been used. The transmission of light through fabrics has been measured on the system LUCIA for image analysis. The porosity of textiles has been evaluated from corresponding construction parameters and idealized models of fabric geometry. The dependencies between the above mentioned characteristics were formalized by using regression analysis.

Modeling of internal geometry of 3D woven fabrics by computation method

This article enumerates a two-phase modeling technique to predict the properties of 3D woven structures. The first phase is devoted to the cross-section modeling of tows, the output of which is utilized in modeling of fabric internal geometry. The output of the modeling helps to predict internal geometry of various 3D constructions for design and development of textile structural composites. An analytical method for calculating the geometric description of the composite unit cell based on the summation of volumes of tows in the three principal directions is presented. The cross-sectional shape and aspect ratio of the stuffer, filler, and binder tows have been taken into consideration. The second phase of the model enables to play with yarn linear density, thread density, number of tow layers, binding structure, and packing factor of tows for predicting areal density, thickness, and volume fraction of the preform fabric before actually manufacturing it. Both the models compute the output values on MATLAB R2010b platform and it has been found that calculated values are in good agreement with measured values.

Hydrophobic treatment of natural fibers and their composites—A review:

There is a growing interest in the development of natural fiber-reinforced composites, most likely due to their wide availability, low cost, environment friendliness, and sustainability. The market size for natural fiber-reinforced composites is projected to reach

Thermodynamics of aerogel-treated nonwoven fabrics at subzero temperatures

5.83 billion by 2019, with a compound annual growth rate of 12.3%. The composite materials reinforced with wood, cotton, jute, flax or other natural fibers fall under this category. Meanwhile, some major factors limiting the large scale production of natural fiber composites include the tendency of natural fiber to absorb water, degradation by microorganisms and sunlight and ultimately low strength and service life. This paper has focused to review the different natural fiber treatments used to reduce the moisture absorption and fiber degradation. The effect of these treatments on the mechanical properties of these composites has also been summarized.

Novelties of 3-D woven composites and nanocomposites

Nonwoven fabrics and aerogel have complementary properties required for good thermal insulation. In this work, the polyester/polyethylene nonwoven thermal wraps treated with amorphous silica aerogel are studied and characterized with regard to thermodynamical properties at subzero temperatures. The characterization of physical structure was done by scanning electron microscope. C-Therm TCi thermal conductivity analyzer was used to measure thermal properties like conductivity, resistance, and effusivity at subzero temperatures. Heat transfer caused by convection through the thermal wraps was measured by particle image velocimetry technique, which allows obtaining information about the current distribution of velocities in two-dimensional array in a flowing fluid. Vector and scalar maps of the fluid flow were caused by thermal convection. The samples were studied for different temperature gradients. On scientific evaluation of results, thermal conductivity and thermal effusivity were found to be differing with respect to different temperatures and fabric density. Thermal resistance showed an increase as the fabric thickness increases. It was observed that fabric density and the aerogel present in the structures have a significant effect on thermal properties of aerogel-treated nonwoven fabrics. The findings in this study are significant and can be used for further research in aerogel-treated nonwoven fabrics.

Modelling and simulation of 3D orthogonal fabrics for composite applications

This research is aimed to investigate the mechanical behaviour of 3-D woven fabrics as compared to 2-D woven fabrics and subsequently to check its suitability for composite applications. Mechanical tests especially related to ballistic protection of these fabrics were carried out to see the effect of fabric structure on its mechanical properties. The tensile test showed higher strength for 3-D fabrics as compared to 2-D fabrics. Improvement in the breaking load and energy absorption of 3-D fabrics was also observed in the impact test. Furthermore, applicability of 2-D and 3-D glass woven fabrics for composites was also studied in this work. An exploratory work has been carried out in the field of three phase composite in which fly ash nanoparticles were incorporated in addition with glass fabrics while preparing composites. These fly ash nanoparticles were prepared by high-energy ball milling technique and its effects on mechanical properties of composites were observed. Three-point bending flexural test showed higher flexural strength and modulus of 3-D woven composite and addition of nanoparticles further enhanced the properties of composites. Impact test analysis revealed that the 3-D woven glass fabric/epoxy composites exhibit superior breaking load and total energy than those with 2-D plain woven fabric as reinforcement.

Optimized preparation of activated carbon nanoparticles from acrylic fibrous wastes

The present paper focuses on geometric and micromechanical modelling of 3D orthogonal fabrics for composite applications and employs meso-finite element (FE) modelling for it. FE modelling of textile composites is a powerful tool for the homogenisation of mechanical properties, study of stress–strain fields inside the unit cell, determination of damage initiation conditions and sites and simulation of damage development and associated deterioration of the homogenised mechanical properties of the composite. Meso-FE can be considered as a part of the micro-meso–macro-multi-level modelling process, with micromodels (fibres in the matrix) providing material properties for homogenised impregnated yarns and fibrous plies, and macromodel (structural analysis) using results of meso-homogenisation.