Till Quadflieg

Sensory carbon fiber based textile-reinforced concrete for smart structures

This article investigates the feasibility of intelligent textile-reinforced concrete structural elements with sensing capabilities. The concept is based on dual use of glass and carbon fiber textiles as reinforcement and, at the same time, as a sensory agent. Experimental investigation demonstrates the feasibility of the concept in two applications: detecting strains in a mechanically loaded textile-reinforced concrete beam and monitoring the interaction of the structural element with a wet environment. By detecting the changes to the integrative electrical resistance of the carbon tow, the ability of the textile to sense strain and exposure to water is demonstrated. For strain sensing, the hybrid reinforcing textile provides electro-mechanical sensing with a gauge factor of the order of 1 and a detectable correlation with the load, strain, and displacement responses. For the detection of wetting, the implementation of the carbon tow in a Wheatstone bridge detects fractional resistance changes in the order of 10−5, a figure that is effectively detected by monitoring the voltage across the bridge. The response to wetting, which is conditioned by the cracking of the beam and the exposure to ionic conductive solutions, provides a mean to monitor the functionality and the structural health of the textile-reinforced concrete beam.

Effects of fabric structures on the tensile properties of warp-knitted fabrics used as concrete reinforcements

High-performance textiles are now widely used in civil engineering applications. This work explores the differences between the tensile properties of weft inlay warp-knitted fabrics of high-strength glass and carbon rovings as concrete reinforcements. In this study, 12 types of warp-knitted fabrics with different stitch patterns, including tricot, cord, and pillar stitches, were produced. The effect of the stitch type on the tensile properties of the fabrics was examined. The stitch type was found to significantly affect the tensile properties of the warp-knitted fabrics. The results showed that the tensile strength of fabrics with tricot and cord stitches is greater than that of fabrics with the pillar stitch. The increase in tensile strength was 14% for fabrics made of glass roving and 21% for fabrics made of carbon rovings. A similar gradation was observed for the Young’s modulus of the fabrics. The Young’s modulus was 11% and 25% higher for glass and carbon fabrics, respectively. The structural parameters of the warp-knitted fabrics, including the geometry of the stitch pattern and the yarn cross-sectional shape in a fabric that affect the tensile properties, were analyzed.

Manufacturing of textiles for civil engineering applications

Abstract This chapter reviews the latest textile developments in the area of civil engineering. The reinforcement of construction parts for structural and civil engineering applications with textiles offers many opportunities, including the manufacture of very thin composite and concrete parts, no risk of corrosion of reinforcement materials, and the ability to manufacture structural parts with complex shapes. The basic materials and manufacturing techniques used for reinforcing textiles are summarized. This chapter presents various techniques, including the manufacture of yarn (twisting, cabling, and commingling) and fabric (weaving, knitting, and nonwoven) structures.

Influence of the fabric construction parameters and roving type on the tensile property retention of high-performance rovings in warp-knitted reinforced fabrics and cement-based composites

In this work, the tensile property retention characteristics of high-performance glass and carbon rovings in warp-knitted reinforced fabrics and cement-based composites used in structural applications were investigated. Three types of warp-knitted fabrics, with differing stitch patterns, and cement-based composites were produced. The tensile strength retention and Young’s modulus retention of the roving in these fabrics and their influence on the properties of cement-based composites were compared on the basis of the stitch type. Samples of warp-knitted fabrics composed of glass fibres and carbon fibres exhibit retention of 76–87% and 65–87.6%, respectively, of the initial strength of the rovings. The highest Young’s modulus retention (∼80%) occurs in the case of the fabric sample composed of glass rovings. The retention of the Young’s modulus in the fabric samples composed of carbon rovings was 37–60%. In addition, the translation of strength from the roving to the fabric and retention of the Young’s modulus in the carbon rovings decreased with increasing strength and modulus, respectively, of the original roving. On the basis of the data presented, we provided guidelines for the possible application of the developed fabrics. As conclusion, it is possible to reduce the cost of the raw materials by using fabrics whose original rovings have low tensile strength and Young’s modulus, but high retention properties.

Carbon rovings as strain sensors for structural health monitoring of engineering materials and structures

A prospective method for structural health monitoring of engineering materials and structures is based on embedded strain sensors in the form of electrically conductive carbon rovings. This article presents the results of the application of carbon rovings and the development of flexible textile fabrics based on these rovings for measuring the deformation in engineering materials, including concrete and polymer- and cement-based composites. The possibility of using carbon rovings as a strain sensor is demonstrated via measurements in tensile and four-point bending tests. The experimental setups and methods for measuring the electrical resistance of carbon roving as a function of strain in the roving, concrete, and composites are described. A good correlation has been found between the electrical resistance–strain curve of the carbon roving (used as a calibration curve) and the measurements in the concrete and polymer composites from tensile tests. The difference in the character of the flexural behavior and the electrical signal in the carbon roving cement-based composite, affected by the stitch type and shape of the carbon roving cross section in textile fabric, was found through four-point bending tests.

Characterization of shear behavior of warp-knitted fabrics applied to composite reinforcement

Different types of textile fabrics are now widely used for reinforcing composite structural parts. In this work, three types of weft-inserted warp-knitted fabrics differing in stitch pattern and composed of glass roving were produced. The shear behavior of the developed fabrics was determined according to stitch type. Three basic stitch types were chosen: tricot, cord, and pillar. The shear behavior was examined by the picture frame test method. It was observed that the stitch type significantly affects the shear behavior of the fabrics. The deformation phases during the fabric shear test were analyzed. To estimate the changes in the shear stiffness of the fabrics, shear moduli were calculated as a function of the shear angle. In general, the fabric with the tricot stitch has the greatest shear resistance than that of fabrics with the cord and pillar stitches. The results of the characterization of shear behavior of the warp-knitted fabrics are presented and discussed.

Classified Catalogue for Textile Based Sensors

Technical textiles are used primarily for their technical functionality in many different industries. For monitoring the functionality of textiles it is possible to integrate sensors into the textile. Since textiles are made of fibres, yarns, two-or three dimensional structures the sensor systems should accordingly be designed as a part of them. Smart textiles are concerned with textile based sensors integrated mechanically and structurally to a textile. The state of the art in developing textile based sensors extends from sensor fibres to over coated yarns and textiles but without using standardized tools. The development of a textile sensor and its interpretation on a specific application has been associated with many investigations into combination of different conductive materials, what is a lengthy and costly developing process. Knowledge has already been generated on textile sensors, which now requires an appropriate classification and structure. A classified catalogue which allows a direct selection of textile based sensor modules on the basis of measured values. The catalogue´s structure follows, apart from the VDI- guideline 2222, of which complex coherences can be arranged and a clear representation can be found. Setting standards in the field of smart textiles helps companies to produce more smart products.

Effect of coating type on the mechanical performance of warp-knitted fabrics and cement-based composites

High-performance textiles are used for reinforcing concrete structural parts. This paper presents a technique for producing coated weft-inserted warp-knitted fabrics for concrete applications. Three types of reinforced fabrics differing in coating type and composed of alkali-resistant-glass rovings resulting in a cement composite matrix were produced. The investigated coatings include potassium silicate, carboxylated styrene butadiene rubber and epoxide. The mechanical properties of the developed fabrics and cement composites were determined according to the coating type. Thereafter, the mechanical performance of the warp-knitted reinforced fabrics was investigated using tensile tests. Finally, the properties of the composites were examined according to the coating type using a four-point bending test. The results of the characterization of the coated weft-inserted warp-knitted reinforced fabrics and cement composites based on them are presented and discussed. It is shown that the coating material has high influence on the composite properties. Samples with potassium silicate showed highest strength at the limit of proportionality, while samples with epoxide showed the highest flexural strength.

Strain measurement in concrete using embedded carbon roving-based sensors

Abstract This paper presents the results of the application of carbon rovings as strain sensors for measuring the strain in concrete. In this work, three types of electrically conductive carbon roving with different characteristics were used. The possibility of using carbon rovings as a strain sensor is demonstrated via measurements in tensile and four point bending tests. The experimental setups and methods for measuring the electrical resistance of carbon roving in the roving and concrete are described. The results of the characterization of the electrical behavior as a function of strain of carbon rovings and concrete are presented and discussed. The obtained results indicate that the strain range of carbon rovings optimally corresponds to the strain range of concrete. This characteristic behavior makes the carbon rovings well suited for the use as strain sensors. A good correlation has been found between the electrical resistance-strain curve of the carbon roving and the measurements in the concrete.