F. Soutinho

Wicking behavior and drying capability of functional knitted fabrics

Liquid transporting and drying rate are two vital factors affecting the physiological comfort of sport garments. In this study, plated knitted fabrics produced with functional fiber yarns in the back of the knit (close to the body), combined with polypropylene or polyester in the face (outer surface) were tested in terms of their wicking behavior and drying rate capacity. Functional knitted fabrics were evaluated by vertical and horizontal wicking tests. The drying capability was assessed by drying rate tests under two different conditions, namely, at 20±2°C and 65±3% relative humidity and, in an oven, at 33±2°C, in order to simulate the human body temperature. The influence of the functional fiber used and that of the ground material, polyester or polypropylene, was analyzed and discussed.

Mechanical behavior of novel sandwich composite panels based on 3D-knitted spacer fabrics

In the present work, the mechanical performance of novel sandwich composite panels based on 3D-knitted spacer fabrics has been investigated. Composite panels were produced using three different types of spacer fabrics having different structural parameters. The sandwich panels were fabricated based on an unsaturated polyester resin using a modified vacuum-assisted resin transfer molding process which allowed the formation of low-density core structures. The produced sandwich composite panels were characterized for flexural, compressive, and impact properties. The effect of different fabric structural parameters (such as cross-thread density, linear density of yarn used in face and core, and structure of face) on the processability and mechanical behavior of composite panels has been thoroughly investigated. The results showed that the composite panels based on spacer fabrics having lesser cross-thread density and made of coarser yarns performed better with respect to compressive and impact properties, whereas the best flexural properties were obtained in case of spacer fabrics with high cross-thread density and made of finer yarns.

Waste Fibre Reinforced Ecocomposites

With a significant production of waste fibrous material, textile companies are now looking for applications where waste materials could be an added-value material. One viable application of these waste materials is in the combination with polymeric matrices, producing composite materials with interesting properties for specific applications, from furniture to thermal and acoustic insulations. The aim of this work was to study the physical and mechanical properties of waste fibre reinforced composites and the influence of different parameters on their mechanical behaviour. Results show that a wide range of different properties and performances may be designed by altering various production parameters, such as thickness of the nonwovens used, time and temperature of the compression moulding, relationship between fibre/matrix ratio, polymeric film used and number of layers.

Improving the stiffness of unidirectionally oriented weft-knitted structures for polymer matrix composite reinforcement

The use of weft-knitted structures in composite reinforcements is limited due to their poor mechanical properties. The tensile behaviour of weft-knitted fabrics is strongly restricted by its loop formation. When this type of structure is used as reinforcement, the mechanical properties of the composite material may be considerably hindered, as the resin may bear the initial load and fail before the load is transferred to the reinforcing fibres. However, weft-knitting is the most suitable technique for the production of 3D fabrics for complex shape composite reinforcements and so their stiffness must be improved. This paper reports on the progress that has been made to improving the modulus of elasticity of glass fibre fleece structures in the coursewise direction, in order to enable the production of tubular or flat preforms for composite materials with adequate stiffness.

Application of braided fibre reinforced composite rods in concrete reinforcement

This paper describes the work that is being done at the University of Minho concerning the development of braided rods for concrete reinforcement. A preliminary research study has been conducted to understand the mechanical behaviour of braided fabrics. Various samples have been produced varying the type of fiber (glass, polyester and aramid), the type of braided fabric (simple, hybrid and core reinforced) and in the latter case, the number of core reinforcing yarns. The tensile properties of these samples have been evaluated and the results presented. The influence of each factor on the tensile properties of braided fabrics has also been analysed and discussed. In order to produce braided reinforced composite rods to use as a concrete reinforcement, a special technique has been developed using a standard vertical braiding machine. The braided reinforced composite materials have been produced in rib structure to improve adhesion between them and the concrete. Special samples have been prepared and tested to evaluate the adherence between both materials involved. The tensile and bending properties of braided reinforced composite rods have been evaluated and the results obtained presented and discussed.

Yarn imaging and advances in measuring yarn characteristics

Abstract: This chapter discusses two integrated fields, the imaging techniques applied to yarn structures, and the latest advances in measuring yarn characteristics. The chapter first reviews the use of digital image processing in yarns, considering its importance, applications and recent advances. The chapter then discusses new developments in measuring yarn characteristics and online systems for measuring yarn quality.