Marina Michalak

Investigation Of Sound Absorption Properties Of Bark Cloth Nonwoven Fabric And Composites

Abstract The quest for sound-absorbing materials that are not only environmentally friendly, but also sustainable is the foremost reason for natural fibre-acoustic materials. Bark cloth is a natural non-woven fabric that is largely produced from Ficus trees. An exploratory investigation of bark cloth a non-woven material and its reinforcement in epoxy polymer composites has been fabricated and investigated for the sound absorption properties so as to find the most suitable applications and also to see whether bark cloth can be used in some applications in place of man-made fibres. Three types of material species were investigated with their respective composites. The fibre morphology showed bark cloth to be a porous fabric that showed promising sound absorption properties at higher frequencies. The sound absorption results of four-layer material selections of Ficus natalensis, Ficus brachypoda and Antiaris toxicaria bark cloth showed sound absorption coefficient of 0.7; 0.71 and 0.91 at f > 6400 Hz, respectively. The bark cloth reinforced laminar epoxy composites had reduced sound absorption coefficients, which ranged from 0.1 to 0.35, which was attributed to decreased porosity and vibration in the bark cloth fibre network.

A smart fabric with increased insulating properties

A new textile fabric prototype providing more heat insulation composed of shape-memory elements was investigated. The shape-memory elements in the form of spirals characterized by two-way action were made of nitinol (NiTi) one-way wires with the inner state transition temperature of 35℃. The fabric prototype developed was made of three layers of nonwovens manufactured from the blends of flax and steel fibers and the two interlayers included spirals, made from NiTi or a reference copper (Cu) wire. The inner layer (heater) was heated by electrical current. The external prototype layers imitated the fabric. Mirrors and an infrared camera were used to measure the thermal properties. The temperature of the external surfaces was analyzed as a function of heating time. At approximately 35℃, a change in the curve of the dependence of temperature on the heating time of the prototype with NiTi elements could be observed; the rate of the temperature increase began to decrease. The width of the interlayer with air and NiTi elements increases by approximately 2.5 mm during heating. The observed phenomenon is caused by the expansion of the NiTi spirals and did not occur with the prototype composed of non-active reference Cu elements. In the final second of heating, the temperature on the external surface of the prototype with NiTi elements was lower by 2–3℃ than that on the prototype with Cu elements. A theoretical model of the system was developed and a satisfactory agreement between the experimental and theoretical results was obtained.

Sound-absorbing green composites based on cellulose ultra-short/ultra-fine fibers

In this paper studies on sound absorption of the thermoplastic composites on the basis of waste natural fibers are presented. Cotton fibers and cellulose ultra-short and ultra-fine fibers obtained from flax fibers following enzymatic and additional mechanical treatment were used as the components of polylactide composites, and their influence on sound absorption behavior was investigated. The composites were obtained from a pressing process of fibrous multilayer structures. The sound absorption properties of three types of composites were compared: composites reinforced by cotton fibers, composites reinforced by cellulose ultra-short and ultra-fine fibers, and composites reinforced by cotton fibers and cellulose ultra-short and ultra-fine fibers. The role of cellulose ultra-short and ultra-fine fibers in changing the sound absorption properties of composites was determined. It has previously been shown that using natural fibers with a thermoplastic polymer results in increased sound absorption. The best improvement of sound absorption can be obtained by combining cotton fibers and cellulose ultra-short and ultra-fine fibers, especially nanofibers, as a reinforcement.

Sound absorption property of nonwoven based composites

Abstract Sound absorbing materials used to provide optimal conditions in rooms can be applied in the form of textiles with a special structure such as nonwovens or fibre-containing composites. Nonwovens can be successfully used to make thermoplastic composites by thermal pressing. This paper presents the comparison of the sound absorbing properties of needled nonwovens and composites made from them. Composites with various densities can be made of nonwovens with various percentage contents of filling and matrix fibres. The sound absorption by composites with similar thickness, about several millimetres, is slightly lower than that by the laminar nonwoven packs used for their making. The optimal content of the filling fibres in the composite, when its sound absorption coefficient reaches the highest values, is at the level of 10 wt.%. With the increase in the content of filling fibres the composite density decreases. In the case of the composite with 10 wt.% of filling fibres, its density is the highest among the composites investigated, and the increase in absorption of high-frequency sounds is the highest. Imparting a relief with a protrusion diameter over 10 mm to the composite surface, we can increase the sound absorption of that composite.

Lateral and Perpendicular Thermal Conductivity Measurement on Textile Double Layers

In this paper, the temperature distribution on a double layered fleece textile was measured experimentally with infrared thermography. A theoretical model based on the thin plate theory was to interpret the results measured. A two dimensional simulation of the same problem was carried out as well. By fitting the experimental data with the models, thermal conductivities in the lateral and perpendicular directions could be determined.

Visualisation of liquid flow phenomena in textiles applied as a wound dressing

Abstract The aim of this work was to visualise liquid transport in textiles. Knowledge of the transport phenomena allows for the design of textiles for various applications, e.g., comfortable to wear filtration and wound dressing. To visualise liquid transport through textiles, three test methods were explored. The first one was the high spatial resolution magnetic resonance imaging (MRI) technique (also referred to as nuclear magnetic resonance (NMR) microscopy). It allowed the observation of the pathways of liquid flow through textiles. In the second method, a thermographic camera was used to record temperature changes and assess the liquid flow in the textile. The third method was using a high-speed video camera to observe the liquid transport within the textile. Two types of textiles were studied: a double-layer knitted fabric and a woven fabric, both made from hydrophilic and hydrophobic fibres (cotton, viscose and polypropylene). The knitted fabrics were tested as a new type of wound dressing, which trans

Research on possible medical use of silk produced by caddisfly larvae of Hydropsyche angustipennis (Trichoptera, Insecta)

Silk products are used in medicine as biomaterials, and are particularly promising as scaffolds in tissue engineering. To date only silkworm and spider silk medical potential has been evaluated, whereas the possible application of the material spun by caddisflies in wet environment has not been examined. Biomedical application of every natural material requires biocompatibility testing and evaluation of unique microbiological and mechanical properties. This article focuses on silk fibers formed in caddisflies cocoons of Hydropsyche angustipennis (Insecta, Trichoptera) larvae. Preliminary biological evaluation shows that trichopteran silk is not cytotoxic to human cells. Caddisfly silk itself does not possess antiseptic properties and thus sterilization is indispensable for its application in medicine. Among tested methods of sterilization and disinfection only thermal methods (tyndallization and autoclaving) enabled complete eradication of bacteria and gave fully sterile material. Caddisfly silk appeared to be resistant to high temperature. Fully sterile fibers can be stored without a loss of breaking force and tensile strength. Our work shows that trichopteran silk has a significant potential to be used as a biomaterial.

A smart textile fabric with two-way action:

The aim of the paper was to develop a prototype of smart textile material with shape memory elements that give variable thermal insulation dependent on the emission-absorption of heat. Shape memory elements were made in the form of spirals of two-way action from nitinol (NiTi) one-way wire. Two groups of samples were made: active and non-active. The active spirals expand at temperatures lower than the characteristic inner state transition temperature and contract as the temperature becomes higher than the transient temperature, which was about 45℃. The non-active spirals do not change dimensions under the influence of heat supply. The material of the layered structure was prepared. The first layer consisted of cotton woven fabric and the second layer featured a system of NiTi spiral elements, while the final layer was made of a thin Teflon foil. The behavior of samples during absorption-emission of heat was studied. Temperature measurements were conducted using an infrared camera; samples were placed on a heater to ensure contact between the Teflon layer and the base, and the temperature was recorded at the sample surface (woven fabric) as a function of the heating time for both active and non-active samples. A theoretical model that makes it possible to determine the time variable thermal parameters of the smart textile material was developed. Good agreement between the experimental and theoretical results was received. The temperature on the surface of the active sample was approximately 10℃ higher at the end of heating than the temperature of the non-active sample after the same heating pattern.

Bio-Based Composites for Sound Absorption

The acoustic thermoplastic composites and a method for their production with the participation of the bio-components were presented. To form composite matrix polylactide fibres (PLA) were used. Natural fibres (flax (LI) and cotton (CO)), straw and cellulose ultra-short/ultra-fine fibres obtained from biomass were used as a reinforcement. Cellulose ultra-short/ultra-fine fibres were obtained from the flax fibres or straw by enzymatic treatment and optionally modified by silane. The tensile stress at maximum load of composites with the sub-microfibres obtained from waste flax fibres after silane modification is twice higher than that of the composite with the submicrofibres without the silane modification. The effect of different kinds of natural materials on the acoustic composites was studied. The addition of the straw increases the values of the sound absorption coefficient are higher because of the additional voids caused by the particles of straw. If as a reinforcement the CO fibres and cellulose sub-microfibres are used, the sound absorption of the composite is higher than for composite with only CO fibres. In the case of sub-microfibres obtained from the waste flax fibres the highest sound absorption and tensile stress of the composites gives the modification by solution of silane in ethanol and water.