Thermo-Mechanical Behaviour of Flax-Fibre Reinforced Epoxy Laminates for Industrial Applications

Abstract

The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum bagging and resin infusion. The stiffness and strength behaviours are investigated under both monotonic and low-cycle fatigue loadings. The analysed material has, in particular, shown a typical bilinear behaviour under pure traction, with a knee yield point occurring at a rather low stress value, after which the material tensile stiffness is significantly reduced. In the present work, such a mechanism is investigated by a phenomenological approach, performing periodical loading/unloading cycles, and repeating tensile tests on previously “yielded” samples to assess the evolution of stiffness behaviour. Infrared thermography is also employed to measure the temperature of specimens during monotonic and cyclic loading. In the first case, the thermal signal is monitored to correlate departures from the thermoelastic behaviour with the onset of energy loss mechanisms. In the case of cyclic loading, the thermoelastic signal and the second harmonic component are both determined in order to investigate the extent of elastic behaviour of the material.

Unidirectional Rubber-Toughened Green Composites Based on PHBV

“…As noted earlier, the stress-strain curves for the composites exhibited a distinct knee. Similar behaviour has been reported previously by Hughes et al [49,50] who attributed its occurrence to irreversible deformation resulting from "re-organization of cellulose fibrils in the direction of the fibre axis" and extension of kink band defects in the fibres.…”

Using FEM simulation to predict structural performances of a sailing dinghy

“…Simulations have been performed in ANSYS r. 15. Different modules of the package have been adopted, in particular: external aerodynamic forces have been calculated in FLUENT via CFD analysis to verify those carried out by analytical equations, ANSYS APDL has been used to resolve the forces and moments equilibrium of the boat, the orthotropic behaviour of the sandwich material [18,19] is modelled in the ACP PrePost and, finally, the structural response of the boat has been calculated in WORKBENCH via FEM analysis.…”

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