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International audience; We propose a new experimental method using a Hassler cell and air injection to measure the permeability of fiber preform while avoiding a race tracking effect. This method was proven to be particularly efficient to measure very low through-thickness permeability of preform fabricated by automated dry fiber placement. To validate the reliability of the permeability measurement, the experiments of viscous liquid infusion into the preform with or without a distribution medium were performed. The experimental data of flow front advancement was compared with the numerical simulation result using the permeability values obtained by the Hassler cell permeability measurement set-up as well as by the liquid infusion experiments. To address the computational cost issue, the model for the equivalent permeability of distribution medium was employed in the numerical simulation of liquid flow. The new concept using air injection and Hassler cell for the fiber preform permeability measurement was shown to be reliable and efficient.; Nous proposons une nouvelle méthode expérimentale utilisant une cellule de Hassler et une injection d'air mesurer la perméabilité de la préforme fibreuse qi permet d'éviter les effets de bord. Cette méthode a été validée pour mesurer les très faibles perméabilités de préforme fabriquée par placement automatisée de fibres sèches. Pour valider le la fiabilité de cette mesure, les expériences d'infusion de préforme avec ou sans un milieu de distribution ont été réalisées. les données expérimentales de l'avancement du front d'écoulement a été comparé avec les résultats de simulation en utilisant les valeurs de perméabilité obtenues par la méthode de Hassler.

The article is devoted to the application of analytical centrifugation for the measurement and analysis of centrifugal ultrafiltration kinetics. The model of centrifugal ultrafiltration of colloids accounting for the cake formation, compression and possible decompression is proposed. The method for the determination of filter cake properties (pressure dependency of specific cake resistance) from the results of batch centrifugal ultrafiltration experiment is presented. The method was tested for the determination of filterability of model samples: aqueous solutions of protein (bovine serum albumin) and nanoparticle suspension (Laponite RD). The pressure dependency of specific cake resistance was determined in the range of 10−500 kPa from the results of centrifugal ultrafiltration experiments at different centrifugal rotation speeds. The obtained values of specific resistance were in good correspondence with those measured in a series of reference constant pressure dead-end filtration tests.

New PHBV/wheat straw fibres biocomposites were produced in such a way to improve the fibre/matrix interface and modulate functional properties of materials. A torrefaction treatment was applied to wheat straw fibres in such a way to increase their hydrophobicity. This improvement led to a better fibre/matrix interfacial adhesion in resultant composites prepared by melt-extrusion, as revealed by SEM observations. The crystallization process was favoured by the presence of torrefied fibres while molecular weight and crystallinity of matrix polymers remained unchanged as compared to untreated fibres. Fibre torrefaction treatment had no significant effect on the mechanical properties of PHBV/wheat straw fibre composites, except for 30 wt.% of torrefied fibres with materials displaying an increased rigidity. It was concluded that improving fibre/matrix adhesion and increasing fibre aspect ratio did not lead to a better preservation of mechanical properties, due to the inevitable presence of microscopic defects in the composite materials. As regards water vapour permeability (WVP), a 30% decrease was first noticed with torrefied fibre contents up to 20 wt.%, which was ascribed to the hydrophobic nature of fibres and improvement of fibre/matrix adhesion. WVP then increased for a fibre content of 30 wt.%, probably due to the creation of percolating pathway. Keywords: Biocomposite, Torrefaction, PHBV, Wheat straw, Mechanical properties, Water vapour permeability