Abstract
Environmentally friendly FRP composites, made of natural fibres and bio-based polymer matrices, may be used as externally bonded reinforcement for civil structures or buildings subjected to moderate outdoor conditions, in replacement of traditional carbon/epoxy systems. However, a major drawback of natural fibers is their sensitivity to moisture, which can affect both the mechanical properties of FRP composites and their adhesive bond with concrete. This research, funded by the French National Research Agency (ANR Project MICRO), aims at studying the influence of hygrothermal ageing on the performances of “green composites” manufactured by hand lay-up process using unidirectional flax fabrics and a bio-based epoxy matrix. The test program consists in subjecting FRP laminates and FRP strengthened concrete slabs to accelerated ageing conditions under various combinations of temperature and humidity. Aged laminates are then periodically characterized by tensile tests and interlaminar shear tests, while the bond properties of concrete/composite assemblies are assessed by pull-off tests. This paper presents the first results of this ongoing program which is scheduled over a period of 2 years. Results are discussed in the light of complementary investigations (water sorption behaviour, microscopic observations and evaluation of the glass transition temperature by differential scanning calorimetry – DSC) in order to relate observed performance evolutions to actual microstructural changes or damage processes taking place in the material.
Highlights
Throughout the past few decades, composite materials have been proven effective for the rehabilitation and strengthening of concrete structures because of their high mechanical properties to weight ratio and their resistance to corrosion
The present study aims at achieving a better understanding of this coupling on the mechanical properties of an innovative bio-composite consisting of a bio-based epoxy matrix reinforced by flax fibres
This paper has presented the first results of a durability study conducted on Fiber-Reinforced Polymer (FFRP) laminates and FFRP strengthened concrete slabs subjected to various accelerated ageing conditions (6 different combinations of temperature and relative humidity)
Summary
Throughout the past few decades, composite materials have been proven effective for the rehabilitation and strengthening of concrete structures because of their high mechanical properties to weight ratio and their resistance to corrosion. Considering their energyconsuming fabrication process and the increase of global concerns towards climate change and reduction of carbon emissions, the search for more eco-friendly material becomes a relevant objective. Multiple studies have proven that the mechanical properties of vegetal fibres composites are strongly affected by water absorption [4,5,6,7,8,9,10], but until now there is no clear understanding of the coupling effect of temperature and moisture absorption in the ageing behaviour of these materials.
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