Influence of moisture uptake on the static, cyclic and dynamic behaviour of unidirectional flax fibre-reinforced epoxy laminates

Abstract

International audienceThis papers aims to characterize the influence of moisture uptake on the mechanical behaviour of unidirectional flax fibre-reinforced epoxy laminates. Monotonic and cyclic tensile tests and free vibration characterization are carried out. Results show that LID flax-epoxy composites, when exposed to hygrothermal conditioning at 70 degrees C and 85% RH, exhibit a diffusion kinetic which follows a one dimensional Fickian behaviour. The mass uptake at equilibrium is approximately 3.3% and the diffusion coefficient 6.5 x 10(-6) m(2) s(-1). Water vapour sorption is shown to induce a significant change in the shape of the tensile stress-strain curve, a decrease in the dynamic elastic modulus of about 20% and a 50% increase in the damping ratio. Contrary to all expectations, water saturation does not degrade the monotonic tensile strength of such a flax-epoxy composites and leads to an increase in the fatigue strength for a high number of cycles. (C) 2016 Elsevier Ltd. All rights reserved

About the fatigue endurance of unidirectional flax-epoxy composite laminates

“…(4) The best fit is obtained with a logarithmic law. The identified  parameter is lower when compared to the value obtained by Bergès et al [4] (17 vs. 20) on a quasi-UD flax-epoxy composite, traducing a better resistance to fatigue. Indeed, the fatigue strength for 10 6 cycles is approximately 200 MPa.…”

“…The material clearly exhibits a nonlinear behaviour and more exactly a bi-phasic behaviour. The nonlinearity is now well-accepted and documented for flax-epoxy composites [2,4,40,41]. For the tape-based material tested in this study, the modulus-strain curve (see Fig.…”

“…The resulting average fibre volume fraction of approximately 61 ±2%. This volumetric composition was determined following the procedure described in [4,37]. A value of 1.47 g.cm -3 was considered for the fibre specific gravity, as recommended by Le Gall et al [38].…”

“…Fatigue of Plant Fibre Composites (PFCs) has been studied in the last few years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], and most of the available results are critically reviewed in a recent paper [16]. It emphasizes that most of the results are collected on flaxepoxy composites.…”

Dynamic Mechanical Behavior Analysis of Flax/Jute Fiber-Reinforced Composites under Salt-Fog Spray Environment

“…Another issue that contributes to a great extent to the low aging resistance of NFRPs under humid environmental conditions is the poor compatibility between hydrophilic natural fibers and several hydrophobic polymeric matrices such as epoxy resins [30,31]. In this regard, some researchers showed that the water resistance of natural fiber-reinforced polymer composites can be improved and their quasi-static mechanical properties under humid environment can be better retained through fiber chemical treatments [32][33][34][35].…”