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Modelling and simulation of the mechanical behaviour of weft-knitted fabrics for technical applications. Part IV: 3D FEA model with a mesh of tetrahedric elements

100%

Araújo M. , Fangueiro R. , Hong H.

Autex Research Journal

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2004

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tom Vol. 4, no. 2

72--80

EN

This paper is in four parts. The first is related to general considerations and experimental analyses, and each of the others is related to different approaches to the theoretical analyses of the mechanical behaviour of weft-knitted fabrics and weft-knitted reinforced composites made of glass fibre. The objective is to find ways of improving the mechanical properties and simulating the mechanical behaviour of knitted fabrics and knitted reinforced composites so that the engineering design of such materials and structures may be improved. In Part IV the technologies for weft-knitted 3D complex shape preform development are surveyed and a third model is presented. This a 3D model based on FEA (finite element analyses). A solid representation of a 2D yarn is built up, and an MES (mechanical event simulation) is applied to obtain a 3D-shaped loop. The final knitted fabric geometry is obtained by interacting this loop with the adjacent loops, according to the dimensional properties of the knitted fabrics and using an MES. Finally, the geometry of the reinforcement inside the composite is built up, and the composite material is divided into small tetrahedric elements to obtain a mesh of finite tetrahedric elements (FEA). The average values of the mechanical properties are obtained with FEA and compared with the experimental ones.

2

Modelling and simulation of the mechanical behaviour of weft-knitted fabrics for technical applications. Part III: 2D hexagonal FEA model with non-linear truss elements

100%

Araújo M. , Fangueiro R. , Hong H.

Autex Research Journal

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2004

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tom Vol. 4, no. 1

25--32

EN

This paper is in four parts. The first is related to general considerations and experimental analyses, and each of the others is related to different approaches to theoretical analyses of the mechanical behaviour of weft-knitted fabrics and weft-knitted reinforced composites made of glass fibre. The objective is to find ways of improving the mechanical properties and simulating the mechanical behaviour of knitted fabrics and knitted reinforced composites, so that the engineering design of such materials and structures may be improved. In Part III the second model is presented, and this is a 2D model based on FEA (finite element analyses). A plain weft-knitted fabric, based on the simple loop structure, is simplified and represented by a 2D hexagonal structure constructed by non-linear truss elements. The characteristics of the truss elements for FEA simulation are obtained from experimental results through an analytical method when a loop is converted to a FEA model. The elongation deformation is simulated in one, two and multiple directions. The model can also be used to calculate a planar knitted fabric for deformation to fit a 3D spherical mould.

3

Process control for total quality in circular knitting

100%

Araújo M. , Catarino A. , Hong H.

Autex Research Journal

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1999/2000

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tom Vol. 1, no. 1

21--29

EN

This paper deals with a problem of major concern to the knitting industry, which is fabric defects. When a defect occurs, the knitting machine has to be stopped and the fault corrected, thus resulting in time loss which is uneconomic. Eventually, the knitted fabric may be rejected if quality requirements are not met. An effective monitoring of the knitting process is required in order to avoid or detect and locate a defect and its cause as soon as possible, avoiding productivity and quality losses. In circular knitting machines the yarn input tension (Ti) can be used as a means of process control, so that defects may be prevented or quickly detected. This was found to be a valuable approach to accomplish this task, since it reflects the general behaviour of the knitting machine. A measuring system is presented, along with the results obtained. Considerations are made around the problem of automatic detection and some approaches are suggested. Finally, some conclusions are drawn from the work developed.

4

Modelling and simulation of the mechanical behaviour of weft-knitted fabrics for technical applications. Part II: 3D model based on the elastica theory

100%

Araújo M. , Fangueiro R. , Hong H.

Autex Research Journal

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2003

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tom Vol. 3, no. 4

166--172

EN

This paper is in four parts. The first is related to general considerations and experimental analyses, and each of the others is related to different approaches to the theoretical analyses of the mechanical behaviour of weft-knitted fabrics and weft-knitted reinforced composites made of glass fibre. The objective is to find ways of improving the mechanical properties and simulating the mechanical behaviour of knitted fabrics and knitted reinforced composites so that the engineering design of such materials and structures may be improved. In Part II the first model is presented, a 3D model based on the classic elastica theory which is used to calculate the load-extension curves of a plain weft-knitted fabric in the coursewise and walewise directions. Good agreement is obtained between theoretical and experimental results.

5

Moisture transmission through textiles. Part II: Evaluation methods and mathematical modelling

88%

Das B. , Das A. , Kothari V. K. , Fanguiero R. , Araújo M.

Autex Research Journal

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2007

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tom Vol. 7, no. 3

194--216

EN

The moisture transmission behaviour of a clothing assembly plays a very important role in influencing its efficiency with respect to thermophysiological body comfort. This paper is in two parts. Part I deals with the processes involved in moisture transmission and the factors at play. Part II is concerned with selecting the measurement techniques which are of great importance in determining fabric factors that influence comfort. The instruments and methods used for testing purposes should adequately simulate the exact conditions for which the fabric will be used, in order to determine the effectiveness of that fabric for a particular wearing situation and environmental condition. The testing methods used and the apparatus developed by different researchers for determining moisture transmission through textiles by different mechanisms are discussed in this paper. Moreover, this part of the paper deals with the mathematical models of liquid and vapour transport through textile materials developed by several scientists in order to understand the exact phenomena involved and to predict the factors affecting the transmission under a particular condition.

6

Moisture transmission through textiles. Part I: Processes involved in moisture transmission and the factors at play

88%

Das B. , Das A. , Kothari V. K. , Fanguiero R. , Araújo M.

Autex Research Journal

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2007

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tom Vol. 7, no. 2

100--110

EN

Moisture transmission through textiles has a great influence on the thermo-physiological comfort of the human body which is maintained by perspiring both in vapour and liquid form. The clothing to be worn should allow this perspiration to be transferred to the atmosphere in order to maintaining the thermal balance of the body. Diffusion, absorption-desorption and convection of vapour perspiration along with wetting and wicking of liquid perspiration play a significant role in maintaining thermo-physiological comfort. The scientific understanding of the processes involved in moisture transmission through textiles and the factors affecting these processes are important to designing fabrics and clothing assemblies with efficient moisture transfer in different environment and workload conditions. This paper is in two parts.Part I focuses on the moisture transmission through textile materials and it discusses the processes involved in moisture transmission and the key influencing factors at play to maintaining comfort. It is underlined that the processes which play the major role in moisture transmission in a particular situation are dependant on the moisture content of the fabric, the type of material used, the perspiration rate and the atmospheric conditions, such as humidity, temperature and wind speed. Part II is concerned with the selection of the measurement techniques which are of great importance in determining fabric factors that influence comfort. The instruments and methods used for testing purposes should adequately simulate the exact conditions for which the fabric will be used, in order to determine the effectiveness of that fabric for a particular wearing situation and environmental condition. The testing methods used and the apparatus developed by different researchers for determining moisture transmission through textiles by different mechanisms are discussed in this paper. Moreover, this part of the paper deals with the mathematical models of liquid and vapour transport through textile materials developed by several scientists in order to understand the exact phenomena involved and to predict the factors affecting the transmission under a particular condition. When designing the comfort of a clothing product for a particular application, the requirements may result from needs concerning the application, the individual wearer and the environmental conditions.