In Situ Detection of Water Leakage for Textile-Reinforced Composites

Abstract

By incorporating electrically conductive yarns into a waterproof membrane, one can detect epoxy resin cracking or liquid leakage. Therefore, this study examined the electrical conductivity variations of several yarns (metallic or carbon-based) for cracking and water detection. The first observations concerned the detectors' feasibility by investigating their conductivity variations during both their resin implementation processes and their resin cracking. Throughout this experiment, two phenomena were detected: the compression and the separation of the fibres by the resin. In addition, the resin cracking had an important role in decreasing the yarns' conductivity. The second part of this study concerned water detection. Two principles were established and implemented, first with yarns and then with yarns incorporated into the resin. First, the principle of absorption was based on the conductivity variation with the yarns' swelling after contact with water. A short circuit was established by the creation of a conductive path when a drop of water was deposited between two conductive, parallel yarns. Through the influence of the yarns' properties, this study explored the metallic yarns' capacity to better detect water with a short circuit and the ability of the carbon-based yarns to detect water by the principle of absorption.

Keywords: composite resin; metallic and carbon-based conductive yarns; water leak detection.

Figure 1

Mould used to form the composite.

Figure 2

Example of the conductive yarn resin in the mould (side and front view).

Figure 3

Three-point bending test scheme.

Figure 4

Principle of water detection by absorption (a) and by a short circuit (b) with the electrically conductive yarns incorporated into a resin plate, and the same schemes—but without resin—for the study of detection principles on conductive yarns only.

Figure 5

Influence of the implementation of the blended spun yarn in the resin on the yarn’s electrical conductivity.

Figure 6

Morphology of the conductive yarns with the resin: (a) SS20/PAC80 (the resin compression of the stainless steel (SS) and the polyacrylate (PAC) fibres) and (b) PA12 + 3%CNT + 14%CB (separation of the multifilaments by the resin).

Figure 7

Morphology of the conductive yarns with the cracking process: separation of the SS fibres inside the spun yarn.

Figure 8

Principle of absorption: influence of hydrophilic property of the non-conductive fibres in the SS-spun yarns: (a) detector sensitivity (Sw); (b) hypothesis of the behaviour of the water-detector yarn.

Figure 9

Principle of absorption—properties influence the following: (a) proportions by weight of an SS/PET yarn and (b) formulation of the CPC.

Figure 10

Short circuit: influence of different yarn properties on the signal: (a) the chemical nature of the non-conductive fibres in the blend, (b) the SS proportion by weight in the SS/PET blend-spun yarns, (c) the physical nature of two 100% SS yarns and (d) the formulation of different yarns in CPC.

Figure 11

Short circuit: physical structure influence for spun and multifilament yarns.