Syed Talha Ali Hamdani

Thermo-Mechanical Behavior of Textile Heating Fabric Based on Silver Coated Polymeric Yarn

This paper presents a study conducted on the thermo-mechanical properties of knitted structures, the methods of manufacture, effect of contact pressure at the structural binding points, on the degree of heating. The test results also present the level of heating produced as a function of the separation between the supply terminals. The study further investigates the rate of heating and cooling of the knitted structures. The work also presents the decay of heating properties of the yarn due to overheating. Thermal images were taken to study the heat distribution over the surface of the knitted fabric. A tensile tester having constant rate of extension was used to stretch the fabric. The behavior of temperature profile of stretched fabric was observed. A comparison of heat generation by plain, rib and interlock structures was studied. It was observed from the series of experiments that there is a minimum threshold force of contact at binding points of a knitted structure is required to pass the electricity. Once this force is achieved, stretching the fabric does not affect the amount of heat produced.

The Application of a Piezo-Resistive Cardiorespiratory Sensor System in an Automobile Safety Belt

Respiratory and heart failure are conditions that can occur with little warning and may also be difficult to predict. Therefore continuous monitoring of these bio-signals is advantageous for ensuring human health. The car safety belt is mainly designed to secure the occupants of the vehicle in the event of an accident. In the current research a prototype safety belt is developed, which is used to acquire respiratory and heart signals, under laboratory conditions. The current safety belt is constructed using a copper ink based nonwoven material, which works based on the piezo-resistive effect due to the pressure exerted on the sensor as a result of expansion of the thorax/abdomen area of the body for respiration and due to the principle of ballistocardiography (BCG) in heart signal sensing. In this research, the development of a theoretical model to qualitatively describe the piezo-resistive material is also presented in order to predict the relative change in the resistance of the piezo-resistive material due to the pressure applied.

Study of electro-thermal properties of pyrrole polymerised knitted fabrics

This paper presents the results of research work carried out to investigate the heating properties of nylon knitted fabric impregnated with a polymerised solution of polypyrrole. The inspection of the molecular polypyrrole electro-conductive pathways responsible for the heating effect of the knitted fabric was investigated using a scanning electron microscope. Further to this, the heat generated by the polypyrrole impregnated fabric was observed under varying power supply terminal separation distances in order to understand the relationship between the length of the polypyrrole electro-conductive fabric and the level of heat generated. The sample with the lowest terminal separation distance i.e. 5 × 1 cm2 produced more localized heat and reached a temperature level of 114℃ in less than three minutes. Additionally a thermo-mechanical characterisation of this knitted heating material was carried out against varying levels of strain and compression. The maximum stress and ultimate strain values of both treated and untreated samples were found to be similar. However, it was observed that the extensibility of the samples affected the generation of heat. The suitability of knitted fabric impregnated with polymerised polypyrrole heating elements for in-car applications where the heating elements may be next to skin was also discussed. The investigation concluded that polypyrrole heating fabric is suitable for next-to-body heating applications which can be engineered by controlling the optimum electrical pathways provided by the network of polypyrrole molecular chains together with the correct power supply levels to work under a defined fabric strain range. The purpose of the current research is to provide a new material that could help to develop heating fabrics with improved textile properties.

The development of novel auxetic woven structure for impact applications

Abstract Nowadays, the auxetic materials, auxetic reinforcement as well as auxetic composite are under the great attention of scientific research due to having excellent mechanical properties. In the current research work, the impact resistance of composite was improved by modifying the four layer through the thickness woven structure, that was used as reinforcement. A comparison was made between the standard four layer through the thickness and modified four layer through the thickness woven structure in terms of auxeticity and penetration. The modified four layer through the thickness woven structure showed auxetic behavior in both warp and weft direction having less penetration resistance as compared to standard sample. The four layer through the thickness non-auxetic woven structures and modified auxetic four layer thorough the thickness woven structures were used as reinforcements to develop composite for impact resistance comparison. The result showed that impact resistance of auxetic composite was 6.7% greater as compared to the non-auxetic composite. It was concluded that the greater value of impact resistance was due to the auxetic behavior of modified four layer through the thickness woven structure.

Study of influence of interlocking patterns on the mechanical performance of 3D multilayer woven composites

Three-dimensional multilayer woven composites are mostly used in high-performance applications due to their excellent out-of-plane mechanical performance. The current research presents an experimental investigation on the mechanical behavior of three-dimensional orthogonal layer-to-layer interlock composites. The glass filament yarn and carbon tows were used as reinforcement in warp and weft directions respectively, whereas epoxy was used as a resin for composite fabrication. Three different types of orthogonal layer to layer interlock namely warp, weft, and bi-directional interlock composites were fabricated and the effect of interlocking pattern on their mechanical performance was evaluated. The evaluation of the mechanical performance was made on the basis of tensile strength, impact strength, flexural strength, and dynamic mechanical analysis of composites in warp and weft directions. It was found that warp and weft interlock composites showed better tensile behavior as compared to bi-directional interlock composite both in the warp and weft directions, due to the presence of less crimp as compared to the bi-directional interlock composite. However, the bi-directional interlock composite exhibited considerably superior impact strength and three-point bending strength as compared to the other structures under investigation. These superior properties of bi-directional interlock composites were achieved by interlocking points in warp and weft directions simultaneously, creating a more compact and isotropic structure. Tan delta values of dynamic mechanical analysis results showed that bi-directional interlock composite displayed the highest capacity of energy dissipation in the warp and weft directions while weft interlock structures displayed highest storage and loss moduli in the warp direction.

Optimization of 3D woven preform for improved mechanical performance

For structural design applications, through-thickness characteristics of reinforcement played a vital role, which is why 3D woven preforms are recommended for such applications. These characteristics are mainly dependent on the fiber and yarn positioning in reinforcement. Although research has been conducted for characterizing woven composites, special attention has not been made on weave pattern parameter which directly affects the mechanical performance of composites. In this research work, 3D orthogonal layer to layer and through thickness woven structures with different interlocking patterns have been thoroughly studied for their mechanical properties, thickness, air permeability and areal density. Natural fibers when used with biodegradable matrix find use in structural, as well as low to medium impact applications for automobiles. Jute yarn was used to produce four-layered 3D woven structures, as synthetic fibers will not give a biodegradable composite part. The focus of this study is to optimize weave pattern, which is robust in design, degradable preforms and easy to reproduce. The main objective of this research focused on the effectiveness of weaving patterns on physical and mechanical properties as well as to optimize the weave pattern for optimum performance. Grey relational analysis was used for the optimization of the robust weave pattern. The results showed that hybrid structures can be useful for improving the properties of the orthogonal layer to layer and through thickness woven structures. It was also noted that weft-way 3D woven structures can provide comparable mechanical properties with warp-way 3D woven structures.

MODELLING THE EFFECT OF WEAVE STRUCTURE AND FABRIC THREAD DENSITY ON MECHANICAL AND COMFORT PROPERTIES OF WOVEN FABRICS

Abstract The paper investigates the effects of weave structure and fabric thread density on the comfort and mechanical properties of various test fabrics woven from polyester/cotton yarns. Three different weave structures, that is, 1/1 plain, 2/1 twill and 3/1 twill, and three different fabric densities were taken as input variables whereas air permeability, overall moisture management capacity, tensile strength and tear strength of fabrics were taken as response variables and a comparison is made of the effect of weave structure and fabric density on the response variables. The results of fabric samples were analysed in Minitab statistical software. The coefficients of determinations (R-sq values) of the regression equations show a good predictive ability of the developed statistical models. The findings of the study may be helpful in deciding appropriate manufacturing specifications of woven fabrics to attain specific comfort and mechanical properties.