Effect of Recycling Cycles on the Mechanical and Damping Properties of Short Alfa Fibre Reinforced Polypropylene Composite

This paper aims at studying the effect of recycling on the static and dynamic properties of short alfa fibre reinforced polypropylene.For this purpose,alfa fibres reinforced composites were elaborated by an injection moulding process and were subjected to different mechanical recycling cycles.Then,non-recycled and recycled materials were subjected to static tests and Dynamic Mechanical Analysis(DMA)to evaluate the effect of recycling on their behaviour.Besides,the effects of alkali and salt water treatments on the static and dynamic properties of the alfa composite were also investigated.The obtained results show that tensile and flexural properties of alfa fibres reinforced composites decrease during recycling cycles.Moreover,the recycling induces a drop in the storage modulus and enhances the loss factor of these composites.The composites with alfa fibre especially the alkali treated composite show the same resistance to recycling as composites with hemp fibres.Further,SEM observations indicate a decrease in the fibres dimension with the recycling cycles,especially for alfa fibres,which can explain the decrease in the properties of the alfa composite during recycling operations.

Hygrothermal/UV Aging Effect on Visual Aspect and Mechanical Properties of Non-Woven Natural-Fiber Composites

This work aims at studying the effect of hygrothermal and UV cyclic aging on the tensile properties and esthetic characteristics of non-woven composites.The composite materials were thermo-compressed from non-woven mats made up of PP and flax or kenaf fibers.This works included evaluating the change in color appearance and analyzing the variations in tensile properties and damage mechanisms,depending on the aging time.The presence of the UV protection film on the composite surface showed its effectiveness against aging.From visual observations and measurement of colorimetric parameters,it has been proved effective in the reduction of the bleaching and yellowing of the composites.As regards the tensile tests,the UV protection film enabled to stabilize the Young’s modulus after 1-week aging for Kenaf/PP and after 3-weeks for Flax/PP.After 4-weeks aging,it halved the number of acoustic emission events related to interfacial decohesion and fiber slippage/pull out for Flax/PP and Kenaf/PP composites.

Effect of Stacking Sequences on the Mechanical and Damping Properties of Flax Glass Fiber Hybrid

The aim of this study is to show the interest of the mechanical and dynamical properties of glass-flax hybrid composites.Therefore,various staking sequences of glass-flax hybrid composites were manufactured and tested in free vibrations.The damping coefficients were identified by fitting the experimental responses of free-free bending vibrations.The obtained results show that the staking sequences and the position of flax fiber layers in the hybrid composites changed the properties,so a classification of different stacking sequences was established.In fact,the hybrid laminate made of two glass external layers placed on both sides of four flax layers is very interesting in term of its mechanical and damping properties.Indeed,it showed better specific bending modulus and loss factor than glass composites with proportions of 31 and 39%,respectively.A study of a structure of this composite has been made to validate the obtained results.

Numerical Modelling of the Transient Hygroscopic Behavior of Flax-Epoxy Composite

This contribution deals with the development of a three-node triangular plane finite element to analyze the transient hygroscopic behavior of 2/2 twill flax fabric-reinforced epoxy composite.Several plates of this material were fabricated using the vacuum infusion process and composite specimens were then cut and aged in tap water at room temperature until saturation.To simplify,a plane modelling of water diffusion in the aged specimens is adopted and Fick’s model is used to describe the water diffusion kinetics.To highlight the heterogeneity of the flax-epoxy samples,the twill flax fabrics waviness is modelled with a sinusoidal undulation.In particular,we show that the proposed finite element formulation allows estimating the flax fiber radial diffusion coefficient by an inverse approach.