Innovating routes for the reused of PP-flax and PP-glass non woven composites: A comparative study

The significant industrial development of non-woven biocomposites requires the implementation of environmentally and economically coherent end-of-life recycling solutions. In this study, we studied the recycling of a non-woven poly-(propylene)-flax composite by injection but also by thermo compression. For comparison, a material with the same architecture but reinforced by glass fibres was studied. Both recycling methods showed strong specificities. Injection recycling leads to efficiently homogenised microstructures of the parts but also to drastically reduced lengths of the fibres, up to 10 times lower than with compression moulding. This method globally promotes high failure strengths while compression moulding, by preserving the length of the fibrous reinforcements, guarantees higher stiffness. This work also highlights the impacts of the length and division of the fibre elements on the microstructure of the injected parts; thus, after a series of compression recycling cycles, injected parts exhibit an important skin-core effect larger than after initial injection recycling cycles, whether in terms of orientation or local fibre volume fraction. As a consequence, after a series of recycling by compression, a new injection cycle has for effect to improve the tensile mechanical performances. For example, the strength and modulus of PP-flax composites are increased by 103% and 75%, respectively. These results highlight the technical feasibility and relevance of implementing these two recycling methods, depending on the volumes or equipment available and the final properties to promote, as they enable the production of new highperformance parts

Influence of the Compression Molding Temperature on VOCs and Odors Produced from Natural Fiber Composite Materials

In the automotive sector, the use of nonwoven preforms consisting of natural and thermoplastic fibers processed by compression molding is well known to manufacture vehicle interior parts. Although these natural fiber composites (NFCs) have undeniable advantages (lightweight, good life cycle assessment, recyclability, etc.), the latter release volatile organic compounds (VOCs) and odors inside the vehicle interior, which remain obstacles to their wide deployment. In this study, the effect of the compressing molding temperature on the VOCs and odors released by the flax/PP nonwoven composites was examined by heating nonwoven preforms in a temperature range up to 240 °C. During the hot-pressing process, real-time and in situ monitoring of the composite materials’ core temperature has been carried out using a thermocouples sensor. A chemical approach based on headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography—mass spectrometry (GC-MS) was used for the VOCs analysis. The olfactory approach is based on the odor intensity scale rated by expert panelists trained in olfaction. The results demonstrate marked changes in the VOCs composition with temperature, thus making it possible to understand the changes in the NFCs odor intensity. The results allow for optimizing the molding temperature to obtain less odorous NFC materials

Influence du taux de porosité sur les propriétés d’un composite non tissé lin/PP

Les non tissés à bases de fibres végétales et de polypropylène sont très souvent utilisés dans les équipements intérieurs des véhicules automobiles car ils combinent d’intéressantes propriétés mécaniques et acoustiques. Cette double fonction est assurée grâce à la création d’une quantité contrôlée de porosités dans les pièces. Cette étude s’intéresse à l’impact du taux de porosités sur les propriétés acoustiques (absorption normale) et mécaniques (traction uniaxiale) de ces biocomposites et en les corrélant à leur microstructure. Les valeurs expérimentales de rigidité se sont avérées similaires à celles déterminées à l’aide d’équations issues de modèles analytiques simples. Enfin, les mécanismes d’endommagement des différents composites ont été étudiés en détail (chargements statiques et cycliques) et des principes d’optimisation du matériau ont été émis

Contribution de l'interface fibre/matrice et du renfort sur les propriétés mécaniques en traction d'un biocomposite non-tissé

International audienc

Exploring two innovative recycling ways for poly-(propylene)-flax non wovens wastes

Biocomposites have major advantage in term of weight saving thanks to lower densities compared to conventional materials; this property also allows a reduction of environmental impacts which is beneficial for the automotive industry. In addition, they maintain rather good mechanical properties after recycling cycles which makes possible to consider other end-of-life scenarios than incineration or landfill. In this work, we studied two potential routes for the recycling of moulding wastes from poly (propylene)-flax nonwovens. By representing close to 25%-wt, these wastes are a major industrial problem, inducing additional recycling or treatment costs. In a first step, the parts were grinded and reincorporated at different weight fractions into virgin nonwovens. Up to 30%-wt of reincorporated wastes, results showed good mechanical performances for recycled nonwovens, especially in bending mode. In a second stage, scraps were grinded and then compounded for injection moulding applications. Their good rheological behavior and ability to conserve fibre lengths during extrusion made possible to formulate competitive materials in terms of tensile performances. (C) 2017 Elsevier Ltd. All rights reserved

Comportement hygromécanique des biocomposites non-tissés soumis à des variations d'humidité

International audienceThis study investigates the evolution of hygromechanical properties of flax/PP nonwoven composites in a wide range of environmental Relative Humidity conditions from 10 to 98% RH. The influence of microstructure with various porosity content (Φ = 5, 30, 50%) on the mechanical and hygroscopic behaviours is studied. The porosity greatly impacts the kinetic of sorption with moisture saturation varying from 9 hours to 15 days with decreasing voids. Tensile behaviour and properties are slightly changed over a range of 10-75% RH but negatively impacted between 75% and 98% RH. Interestingly, unlike the tangent tensile modulus and strain at rupture of flax/PP composites, the yield strength increases until 50% RH and stabilizes over this point; compressive stresses at the fibre/matrix interface induced by flax fibres hygroexpansion are proposed to explain this trend. A quasi-monotonous decrease is also observed in bending properties with the increase in water content in the material.Ce travail a pour objectif d'étudier l'évolution des propriétés hygromécaniques des composites non-tissés lin/PP dans une large gamme d'humidité relative allant de 10 à 98% RH. L'influence de la microstructure sur le comportement hygroscopique et mécanique est étudiée avec des taux de porosité variables (Φ = 5, 30, 50%). La porosité a un impact important sur la cinétique de sorption avec une saturation en humidité variant de 9 heures à 15 jours avec moins de porosité. En traction, le comportement et les propriétés mécaniques sont légèrement modifiés sur une plage de 10-75%HR mais ont un impact négatif entre 75% et 98% RH. Il est intéressant de noter que, contrairement au module tangent de traction et à la déformation à la rupture des composites lin/PP, la contrainte maximale augmente dans un premier temps avant de se stabiliser pour de forts taux d'humidités. Ceci s'explique par l'importance des contraintes de compression à l'interface fibre/matrice induites par l'hygroexpansion des fibres de lin. En flexion, on observe une diminution quasi-monotone des propriétés avec l'augmentation de la teneur en eau dans le matériau

Oriented granulometry to quantify fibre orientation distributions in synthetic and plant fibre composite preforms

International audienceFibre orientation is an essential factor governing the mechanical properties of composite materials. This study proposes an original method based on gray-level granulometry to analyse the fibre orientation distribution (FOD) of synthetic and natural fibre reinforcements aiming composite applications. An orientation maps is computed from SEM images and frequency of fibre orientation is graphically illustrated for each angular direction. First, glass fibre nonwoven and unidirectional preforms were analysed as a model to validate the method before testing their flax fibre counterparts. Differences in structural organisations were found between flax and glass fibre reinforcement FOD due to the specific structure and mechanical behaviour of plant fibres but also to the preform manufacturing process. Promising results were obtained confirming the reliability of this novel numerical method for fibre orientation determination