4 - Bonds in textile-reinforced concrete composites

Abstract

A significant number of experimental and analytical investigations have characterized the bond between short fibers and the cement matrix, exploring different types of single fibers of high and low modulus with different geometries. The bonding between fabric reinforcement and cement-based matrix is much more complicated, due to the function of the yarns transverse to the load direction and the complex geometries of the individual reinforcing yarns making up the fabric, which provide anchorage, as well as the mono- or multifilament nature of the yarn. Modern textile technology offers a wide variety of fabrics with great design flexibility and various fiber geometries. Variables in such fabrics include their geometries and distributions of the fibers in two and three dimensions which can highly influence their bond with the cement matrix; yet, the bonding mechanism and the microstructure in the vicinity of the yarn/fabric, ( i.e., at the yarn (fabric)-matrix interface) can be rather different, depending on the form of the yarn (mono- or multifilament), the fabric and its yarn geometry, and the composition of the yarn (fiber) material. The textile-matrix bond strongly influences the entire behavior of the composite, its strength, ductility and toughness. This chapter will discuss the main bonding mechanisms and the various parameters influencing them: multifilament yarns, including yarn coating and filling; yarn geometry; and fabric geometry as well as the main concepts of bond characterization and bond modelling of fabrics in cement-based composites.