Optimising FRP Reinforcement Layout by Using Embroidery Technology

Abstract

Fibre-reinforced polymers (FRPs) are characterised by an anisotropic behaviour, with high tensile strength in the longitudinal direction but being very sensitive to transverse pressure. Traditional rein-forcement principles for steel-reinforced structures that aim at an ease of handling rather than to align the reinforcement according to the principal stresses thus result in a low utilisation rate if trans-ferred one by one to FRP-reinforced structures. New manufacturing methods for FRP textile rein-forcements, however, allow to overcome these shortcomings. In this paper, we explore the potential of embroidery technology to produce a stress-aligned FRP textile reinforcement for a simply sup-ported beam loaded by a single load in midspan (three-point bending test). The beam itself is shape-optimised to minimise cement consumption, making the geometry more complex and thus challeng-ing to reinforce. The optimum reinforcement design was found by linear elastic analysis of the beam and automatically manufactured according to the CAD file derived from the principal stresses. While only two-dimensional reinforcement can usually be produced with embroidery technology, a three-dimensional reinforcement cage can be created by folding the reinforcement prior to the impregna-tion process. The following tests on beams reinforced with such stress-aligned textiles showed very promising results. Compared to a conventional orthogonal reinforcement pattern, the failure load was more than twofold because the crack opening of the governing shear crack, which led to failure in the reference beam, could be limited with the stress-aligned reinforcement.