| Elastic knitted fabric with excellent elasticity and resilience is widely used in tight-fitting suit, swimsuit, stockings and medical bandages, etc. With the continuous improvement of living standards, consumers proposed higher requirement according to garment pressure comfort, functionality, safety and health, which leads to a research hotspot.Garment pressure is one of the important factors for evaluation of compression garment comfort, function, and security. The term "compression garment" refers to a garment which applies pressure to specific areas of the human body. An inappropriate compression garment will affect the energy, work efficiency, and health of the wearer. Insufficient pressure will limit the efficiency, and perhaps reduce the aesthetic appeal of the garment. Too much pressure will result in fatigue, reduce heart and lung functions, and perhaps cause serious damage to health. So the optional measurement methods and systems are crucial for its evaluation. In this thesis, developed pressure measuring system for compression fabric evaluation during its static and dynamic status; improved the smart mannequin system for pressure distributions; and developed flexible pressure sensor for pressure distribution. The content of this dissertation is mainly included four parts as following:1. The relationship between mechanical-physical properties and garment pressure for compression fabricsThe mechanical-physical properties of dozens of elastic knitted fabrics were measured using a KESF standard evaluation system and YG061 tensile evaluation system in laboratory with a controlled environment. Examined the structure characteristics and mechanical-physical properties, and to determine the influence of these properties on garment pressure performance, as well as to establish the quantitative relationships between materials mechanical-physical properties and corresponding pressure functional profiles. Grey system theory was used to identify the significance of the differences of individual mechanical characteristics of elastic fabrics. The developed relationships between pressure magnitude and material mechanical properties provided a rational and practical approach for assessing and predicting the performance of a compression garment.2. The static and dynamic pressure performance evaluation and characterizationA measuring system was developed for static and dynamic pressure evaluation, which is composed of three components, including pressure measuring device, displacement driving device, and data acquisition device. Pressure measuring device is composed of a rigid hemisphere, three high-precision pressure sensors, and sample-holding device. Three sensors are distributed on surface of hemisphere, sensing static pressure and dynamic pressure during hemisphere downward-upward motion. Displacement driving device is composed of main frame, a voltage/frequency converter and a driving motor. The hemisphere with sensors vertical moves to press on fabric sample at predetermined press depth, velocities, and standing time under control of the displacement driving device, the sample deforms to some extent and produces pressure on the surface of hemisphere. The data acquisition device is composed of a signal processor, data collection software, and PC. The pressure values are displayed simultaneously.In order to quantify the static and dynamic behavior of the compression fabric we establish the measure parameters such as press-depth, press-velocity, standing time and etc, also introduce three new indexes:the dynamic pressure stiffness index, static pressure fatigue and dynamic pressure fatigue. Stiffness is defined as the increment in pressure when the elongation increased or decreased by 1 cm. The stiffness of compression garment is important for their function. The static and dynamic fatigue can give information about pressure decay when fabrics undergoing repeated stretch and relaxation.Dozens of elastic fabrics are tested on the measuring system, their static, dynamic and pressure decay behaviors are evaluated in the extension range of 10%to 40%. The garment pressure performances are analyzed among fabrics with varied yarn fineness, Spandex fineness, structure, etc.3. Pressure distributions on a smart mannequin systemA smart mannequin with the dimension of a standard female body was improved for measuring garment pressure. The mannequin has a rigid internal layer and covered with a soft surface, and eight built-in pressure sensors are distributed on its surface. The sensors sense pressure imposed by wearing garment and fed data into an acquisition device simultaneously. The mannequin can extends transversely at the antemedial and postmedial line to the maximal level of 5 cm, which may imitate the dimensions of different human body. Dozens of compression garments made from elastic fabrics knitted were tested. Results show that the pressure distributions exhibit obvious difference among measuring points, also different at the same point while mannequin dimensions are varied, and the controlled Spandex feeding rate causes pressure variations among the specimens. This smart mannequin system provides a novel tool for evaluating the pressure performance of compression garments, and gives reliable data for functional product development.4. Flexible sensor for pressure measurementPVDF nano-fibrous membrane which was light weight, flexible, breathability, wearable, prepared by electrospinning technique. The electrospinning parameters such as the voltage, feeding rate, tip-to-collector distance, etc, were well controlled. More than 4 hours electrospinning time was needed for a certain thickness of PVDF nano-fibrous membrane.The morphology of PVDF nanofiber is determined by scanning electron microscopy (SEM), and crystal structure was evaluated by FTIR spectroscopy and X-Ray Diffractometer. The PVDF fibrous membranes were well designed and fabricated for tactile sensor. The sensor consists of three main parts, flexible electrode, PVDF fibrous membrane, and fixed electrode. The flexible electrode consists of ITO layer and plastic payer, ITO as the conducting polymer first was deposited on the plastic film as the top electrode, the plastic film as an insulator film protests the whole prototype avoiding destroy when the hammer hits. PVDF nano-fibrous membrane as the tactile-sensing element, connected with top and bottom electrodes by silver painter. The rigid electrode also consists of two layers, ITO and glass. ITO was deposited on the glass as the bottom electrode, the glass as a substrate for the bottom electrode and a platform supports the whole prototype. The deformation on PVDF fibrous membrane was applied by the tip of a load cell, which was bonded to a controlled hammer. The electric signals were obtained through home-made circuit and they were connected to an Oscilloscope. We found the feasibility of applying PVDF fibrous membranes prepared through electrospinning technology, to be flexible human-related tactile sensors.The results systematically and clearly show that the quantitative relationships between materials mechanical-physical properties and corresponding pressure functional profiles, the evaluation method for elastic knitted fabric function, including measuring systems, procedure, parameters and indexes.In this thesis, a smart mannequin was also improved, which 8 pressure sensors were distributed in fixed points for garment pressure measurement. The mannequin can extends transversely at the antemedial and postmedial line to the maximal level of 5 cm, which may imitate the dimensions of different human body. We found the feasibility of applying PVDF fibrous membranes prepared through electrospinning technology, to be flexible human-related tactile sensors.
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