The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Joanne Yip - One of the best experts on this subject based on the ideXlab platform.
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Study of three-dimensional spacer fabrics : physical and mechanical properties
Journal of Materials Processing Technology, 2008Co-Authors: Joanne YipAbstract:Spacer is a three-dimensional Knitted fabric consisting of two outer textile substrates which are joined together and kept apart by spacer yarns. Spacer fabrics are used for environmental reasons, which can be used in different product groups such as mobile textiles (car seat covers, dashboard cover), industrial textiles (composites), medical textiles (anti-decubitus blankets), sports textiles and foundation garments (bra cups, pads for swimwear). In this study, the characteristics of different spacer fabrics including low-stress mechanical properties, air permeability and thermal conductivity were investigated. Low-stress mechanical properties obtained by the KES-fabric evaluation system revealed that all tensile, bending and compression properties of spacer fabrics are greatly depending on the type of spacer fabric (Warp Knit or weft Knit), the type of spacer yarn used (monofilament or multifilament), the yarn count of the spacer yarn, the stitch density and the spacer yarn configuration. Air permeability and thermal conductivity of spacer fabric are closely related to the fabric density. This experimental work suggests that carefully selecting the spacer fabric according to the envisaged application is of primary importance.
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Study of three-dimensional spacer fabrics:
Journal of Materials Processing Technology, 2008Co-Authors: Joanne YipAbstract:Spacer is a three-dimensional Knitted fabric consisting of two outer textile substrates which are joined together and kept apart by spacer yarns. Spacer fabrics are used for environmental reasons, which can be used in different product groups such as mobile textiles (car seat covers, dashboard cover), industrial textiles (composites), medical textiles (anti-decubitus blankets), sports textiles and foundation garments (bra cups, pads for swimwear). In this study, the characteristics of different spacer fabrics including low-stress mechanical properties, air permeability and thermal conductivity were investigated. Low-stress mechanical properties obtained by the KES-fabric evaluation system revealed that all tensile, bending and compression properties of spacer fabrics are greatly depending on the type of spacer fabric (Warp Knit or weft Knit), the type of spacer yarn used (monofilament or multifilament), the yarn count of the spacer yarn, the stitch density and the spacer yarn configuration. Air permeability and thermal conductivity of spacer fabric are closely related to.the fabric density. This experimental work suggests that carefully selecting the spacer fabric according to the envisaged application is of primary importance.Institute of Textiles and Clothin
Hyung Woo Kim - One of the best experts on this subject based on the ideXlab platform.
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effects of through the thickness stitches on the elastic behavior of multi axial Warp Knit fabric composites
Composite Structures, 2006Co-Authors: Heoungjae Chu, Hyung Woo KimAbstract:In order to improve the resistance to delamination and some in-plane and out-of-plane properties of composite materials for structural integrity, through-the-thickness reinforcement must be provided. The reinforcement is achieved by using the stitched multi-axial Warp Knit (MWK) fabrics as preforms for the fabrication of composite structures. In this study, the influence of stitches on the elastic behavior of MWK fabric composites under tensile and shear loadings was investigated by utilizing a unified micromechanical model. In the analysis, the in situ constituent properties and fiber volume ratios of insertion and stitching fibers determined from the geometric parameters set by the representative volume were used. The crucial step in the analysis was to correlate the averaged stress states in the constituents by adopting the bridging matrix. The experimental results were compared with the predicted results. It was found that the predicted results are in reasonably good agreement with the experimental results.
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Elastic Behaviors of Stitched Multi-Axial Warp Knit Fabric Composites
Key Engineering Materials, 2006Co-Authors: Heoung Jae Chun, Hyung Woo Kim, Joon Hyung ByunAbstract:The purposes of stitching multi-axial Warp Knitted fabric preform prior to the fabrication of the composite materials by resin-transfer molding technique are to improve the resistance to delamination and to increase the out-of-plane properties of the composite materials for structural integrity. The influence of the through-the-thickness stitching on the elastic properties and behaviors of the multi-axial Warp Knit fabric composites is studied. An analytical model based on the representative volume is proposed to predict the elastic properties of the stitched multi-axial Warp Knit fabric composite materials. The fiber volume ratios determined by geometric parameters set by the representative volume and elastic behaviors of the in-situ constituent materials are used for the predictions. The crucial step in the analysis is to correlate the averaged stress states in the constituents by adopting bridging matrix. The predicted results are compared with the experimental results. It is found that the predicted results are in reasonably good agreement with the experimental results.
John E Masters - One of the best experts on this subject based on the ideXlab platform.
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translaminar fracture toughness of a composite wing skin made of stitched Warp Knit fabric
1997Co-Authors: John E MastersAbstract:A series of tests were conducted to measure the fracture toughness of carbon/epoxy composites. The composites were made from Warp-Knit carbon fabric and infiltrated with epoxy using a resin-film-infusion process. The fabric, which was designed by McDonnell Douglas for the skin of an all-composite subsonic transport wing, contained fibers in the 0 deg, +/-45 deg, and 90 deg directions. Layers of fabric were stacked and stitched together with Kevlar yarn to form a 3-dimensional preform. Three types of test specimens were evaluated: compact tension, center notch tension, and edge notch tension. The effects of specimen size and crack length on fracture toughness were measured for each specimen type. These data provide information on the effectiveness of the test methods and on general trends in the material response. The scope of the investigation was limited by the material that was available.
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Translaminar Fracture Toughness of a Composite Wing Skin Made of Stitched Warp-Knit Fabric
1997Co-Authors: John E MastersAbstract:: A series of tests were conducted to measure the fracture toughness of carbon/epoxy composites. The composites were made from Warp-Knit carbon fabric and infiltrated with epoxy using a resin-film-infusion process. The fabric, which was designed by McDonnell Douglas for the skin of an all-composite subsonic transport wing, contained fibers in the 0°, ±45°, and 90° directions. Layers of fabric were stacked and stitched together with DuPont KevlarÒ yarn to form a 3-dimensional preform. Three types of test specimens were evaluated: compact tension, center notch tension, and edge notch tension. The effects of specimen size and crack length on fracture toughness were measured for each specimen type. These data provide information on the effectiveness of the test methods and on general trends in the material response. The scope of the investigation was limited by the material that was available. Introduction McDonnell Douglas will design and build an all-composite wing for a commercial trans..
Stepan V. Lomov - One of the best experts on this subject based on the ideXlab platform.
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Virtual textile composites software WiseTex: Integration with micro-mechanical, permeability and structural analysis
2014Co-Authors: Stepan V. Lomov, Ignaas Verpoest, Enrique Bernal, Fabrice Boust, Valter Carvelli, Francois Delerue, Patrick De Luca, Laurent Dufort, Satori Hirosawa, Gert HuysmansAbstract:SUMMARY: Internal geometry of textile reinforcement is an important factor of the reinforcement performance during the composite manufacturing and in the service life of the composite material. When a 3D shaped composite part is concerned, the reinforced is locally deformed (compressed, stretched and sheared), and the geometrical model should account for this deformation. The software package WiseTex implements a generalised description of internal structure of textile reinforcement on the unit cell level, integrated with mechanical models of relaxed and deformed state of 2D and 3D woven, two- and three-axial braided, weft-Knitted and non-crimp Warp-Knit stitched fabrics and laminates. It is integrated with modelling of resin flow, micro-mechanical calculations of properties of composite and micro-macro analysis of composite parts, finite element models and virtual reality software. The paper describes this family of models, which use a unified description of the geometry of th
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virtual textile composites software wisetex integration with micro mechanical permeability and structural analysis
Composites Science and Technology, 2005Co-Authors: Ignaas Verpoest, Stepan V. LomovAbstract:The internal geometry of textile reinforcements is an important factor of the reinforcement performance during composite manufacturing and in the service life of the composite material. When a 3D-shaped composite part is concerned, the reinforcement is locally deformed (compressed, stretched and sheared), and any model describing the internal geometry of the reinforcement should account for this deformation. The software package WiseTex implements a generalised description of internal structure of textile reinforcements on the unit cell level, integrated with mechanical models of the relaxed and deformed state of 2D- and 3D-woven, two- and three-axial braided, weft-Knitted and non-crimp Warp-Knit stitched fabrics and laminates. It is integrated with modelling of resin flow, micro-mechanical calculations of properties of textile based composites and micro–macro analysis of composite parts, finite element models and virtual reality software. The paper describes this family of models, which use a unified description of the geometry of the reinforcement unit cell. 2005 Elsevier Ltd. All rights reserved.
Dexter H. Benson - One of the best experts on this subject based on the ideXlab platform.
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Development of Textile Reinforced Composites for Aircraft Structures
1998Co-Authors: Dexter H. BensonAbstract:NASA has been a leader in development of composite materials for aircraft applications during the past 25 years. In the early 1980's NASA and others conducted research to improve damage tolerance of composite structures through the use of toughened resins but these resins were not cost-effective. The aircraft industry wanted affordable, robust structures that could withstand the rigors of flight service with minimal damage. The cost and damage tolerance barriers of conventional laminated composites led NASA to focus on new concepts in composites which would incorporate the automated manufacturing methods of the textiles industry and which would incorporate through-the-thickness reinforcements. The NASA Advanced Composites Technology (ACT) Program provided the resources to extensively investigate the application of textile processes to next generation aircraft wing and fuselage structures. This paper discusses advanced textile material forms that have been developed, innovative machine concepts and key technology advancements required for future application of textile reinforced composites in commercial transport aircraft. Multiaxial Warp Knitting, triaxial braiding and through-the-thickness stitching are the three textile processes that have surfaced as the most promising for further development. Textile reinforced composite structural elements that have been developed in the NASA ACT Program are discussed. Included are braided fuselage frames and window-belt reinforcements, woven/stitched lower fuselage side panels, stitched multiaxial Warp Knit wing skins, and braided wing stiffeners. In addition, low-cost processing concepts such as resin transfer molding (RTM), resin film infusion (RFI), and vacuum-assisted resin transfer molding (VARTM) are discussed. Process modeling concepts to predict resin flow and cure in textile preforms are also discussed
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Verification of a three-dimensional resin transfer molding process simulation model
1995Co-Authors: Dexter H. Benson, Fingerson, John C., Loos, Alfred C.Abstract:Experimental evidence was obtained to complete the verification of the parameters needed for input to a three-dimensional finite element model simulating the resin flow and cure through an orthotropic fabric preform. The material characterizations completed include resin kinetics and viscosity models, as well as preform permeability and compaction models. The steady-state and advancing front permeability measurement methods are compared. The results indicate that both methods yield similar permeabilities for a plain weave, bi-axial fiberglass fabric. Also, a method to determine principal directions and permeabilities is discussed and results are shown for a multi-axial Warp Knit preform. The flow of resin through a blade-stiffened preform was modeled and experiments were completed to verify the results. The predicted inlet pressure was approximately 65% of the measured value. A parametric study was performed to explain differences in measured and predicted flow front advancement and inlet pressures. Furthermore, PR-500 epoxy resin/IM7 8HS carbon fabric flat panels were fabricated by the Resin Transfer Molding process. Tests were completed utilizing both perimeter injection and center-port injection as resin inlet boundary conditions. The mold was instrumented with FDEMS sensors, pressure transducers, and thermocouples to monitor the process conditions. Results include a comparison of predicted and measured inlet pressures and flow front position. For the perimeter injection case, the measured inlet pressure and flow front results compared well to the predicted results. The results of the center-port injection case showed that the predicted inlet pressure was approximately 50% of the measured inlet pressure. Also, measured flow front position data did not agree well with the predicted results. Possible reasons for error include fiber deformation at the resin inlet and a lag in FDEMS sensor wet-out due to low mold pressures
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Performance of resin transfer molded multiaxial Warp Knit composites
1993Co-Authors: Dexter H. Benson, Hasko, Gregory H.Abstract:Composite materials that are subjected to complex loads have traditionally been fabricated with multidirectionally oriented prepreg tape materials. Some of the problems associated with this type of construction include low delamination resistance, poor out-of-plane strength, and labor intensive fabrication processes. Textile reinforced composites with through-the-thickness reinforcement have the potential to solve some of these problems. Recently, a relatively new class of noncrimp fabrics designated as multiaxial Warp Knits have been developed to minimize some of the high cost and damage tolerance concerns. Multiple stacks of Warp Knit fabrics can be Knitted or stitched together to reduce layup labor cost. The through-the-thickness reinforcement can provide significant improvements in damage tolerance and out-of-plane strength. Multilayer Knitted/stitched preforms, in conjunction with resin transfer molding (RTM), offer potential for significant cost savings in fabrication of primary aircraft structures. The objectives of this investigation were to conduct RTM processing studies and to characterize the mechanical behavior of composites reinforced with three multiaxial Warp Knit fabrics. The three fabrics investigated were produced by Hexcel and Milliken in the United States, and Saerbeck in Germany. Two resin systems, British Petroleum E9O5L and 3M PR 500, were characterized for RTM processing. The performance of Hexcel and Milliken quasi-isotropic Knitted fabrics are compared to conventional prepreg tape laminates. The performance of the Saerbeck fabric is compared to uniweave wing skin layups being investigated by Douglas Aircraft Company in the NASA Advanced Composites Technology (ACT) program. Tests conducted include tension, open hole tension, compression, open hole compression, and compression after impact. The effects of fabric defects, such as misaligned fibers and gaps between tows, on material performance are also discussed. Estimated material and labor cost savings are projected for the Saerbeck fabric as compared to uniweave fabric currently being used by Douglas in the NASA ACT wing development program
