Vegetal-FRCM Failure under Partial Interaction Mechanism

Abstract

Featured Application: The reinforcement of concrete structures using FRCM is a rather novelty approach that overcomes some of the drawbacks of organic composites such as carbon fiber CFRP. Moreover, the use of vegetal fabrics has a direct effect on the carbon footprint. Some calculations deal with a full composite action between the matrix and the fibers. Nevertheless, it has been noticed that sometimes the chemical and mechanical adherence between the cementitious matrix and the vegetal fabric does not perform as a perfect bond, and it is necessary to take into account that the matrix–fiber bond is weak. This research provides insight into the limits of the strength for these situations. Partial interaction allows the composite to strengthen with larger deformation while maintaining an interesting ultimate capacity. The characterization of this type of performance may help to design resilient solutions for concrete structures under critical bonding situations produced by ambient or manufacturing reasons. FRCM is a strengthening system based on composite material made of a cementitious matrix and fabrics. This strengthening system has been studied and researched, obtaining analytical predictive models where it is common to assume full composite action between components. Through using non-typical materials for these composites, it has been seen that, in some cases, the previous assumption cannot be taken. In this situation, traditional analytical models such as ACK or tri-linear ones do not offer a reasonable prediction. This work researches the behavior of synthetic and naturally coated vegetal-FRCM with partial interaction through the characterization of the materials through tensile tests. Yarns, meshes and different FRCM coupons were manufactured and mechanically tested using different types of coatings and fabrics. The use of colophony and Arabic gum as natural coatings provided similar mechanical properties to the cotton and hemp yarns and meshes conformed. Partial interaction was found when using epoxy as a natural resin to coat the reinforcement while maintaining the mechanical properties in the same order of magnitude. A new two-stage model is proposed to fit stress–strain mechanical test, and it is reliable and accurate for cotton specimens.