No abstract

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.

Auxetic materials are under great attention of researchers due to their excellent mechanical response under certain conditions. Previous works have been carried out in knitted or uni-stretch woven fabrics. In the present study, three-dimensional (3D) woven structures were produced and the effect of float length of ground weave and binding yarn on auxeticity of the fabric was investigated. Eight different 3D orthogonal woven structures/reinforcements were produced on rapier dobby loom by changing the float length in ground weave and binding yarns. Hand layup technique was used for composite fabrication, while green epoxy resin was used as a matrix. For investigating the auxeticity, 3D reinforcement samples were subjected to tensile loading and change in their thickness was measured. The results showed that 3D woven reinforcements with equal and maximum float length of ground weave and binding yarn showed greater auxetic behavior, because both weaves support each other and room for opening of structure increases. As the difference between the float length of ground weave and binding yarns increases, the auxeticity of reinforcement decreases because the ground weave and binding yarn cancel out the effect of each other. Moreover, the impact energy absorption of the developed composites was found to increase with the increase in float length, justifying that the structures are auxetic in nature.

No abstract

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.

Analiza comparativă a proprietăților firelor Siro cu filare compactă pneumatică și cu inele 245-249 GUIZHEN KE, JIAFENG PEI, KUNDI ZHU Prepararea și proprietățile materialelor compozite PAN/LA-SA realizate prin electrofilare 250-255 SHU-QIANG LIU, GAI-HONG WU, YI CUI, HONG-XIA GUO Analiza mecanismului de finisare rezistentă la contracție asupra țesăturii de mătase/cânepă 256-262 ASIF ELAHI MANGAT, LUBOS HES, VLADIMIR BAJZIK, FUNDA BUYUK, MUDASSAR ABBAS Modelul absorbției termice a tricotului patent în stare uscată și autentificarea experimentală a acestuia 263-268 DANIELA NEGRU, LILIANA BUHU, EMIL LOGHIN, IONUT DULGHERIU, ADRIAN BUHU Absorbția și transferul de umiditate prin materiale tricotate din fibre naturale și artificiale 269-274 TÜLAY GÜLÜMSER Rolul microcapsulelor în mascarea mirosurilor neplăcute ale țesăturilor de bumbac 275

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.

No abstract