Micro- and macro-impregnation of fabrics using thermoplastic matrices

Abstract

In this work, a method developed for the measurement of the transversal permeability of fibrous reinforcement is presented. The permeability of a reinforcement is defined by the Darcy equation and can be obtained once the pressure drop through the reinforcement and the viscosity and average velocity of the fluid are known. The method used in this work is based on a proper modification of a capillary rheometer, obtained by substituting the capillary with a tool, capable of sustaining the reinforcement during reinforcement impregnation and through thickness flow. The developed device was used to measure the pressure built during the flow at different velocities of the rheometer piston. The impregnation tests were performed at different temperatures using a high-viscosity matrix characterized by a Newtonian behaviour. At each temperature, pressure versus velocity plots showed two distinct zones, each characterized by a different slope. The slope observed at low pressures was higher than the slope observed at pressures, suggesting an increase in the permeability with increasing pressure or velocity. The double slope was attributed to the existence of two different impregnation mechanisms, the first one being characteristic of the flow of the matrix around the reinforcement bundles and the second is the characteristic of the flow of the matrix inside each bundle. Dimensionless analysis models and scanning electron micrographs were used to support that the slope of the first portion of the plot is due to inter-bundle flow, whereas the slope of the second portion is due to global flow including both inter-and intra-bundle flow.

A Perspective on the Prowaste Concept: Efficient Utilization of Plastic Waste through Product Design and Process Innovation

“…Nevertheless, each bundle is completely dry, and no matrix is present inside. Therefore it is possible to conclude that macro-impregnation occurs, but no micro-impregnation [ 14 ]. The pultruded carbon reinforced rods from BASF series Mbar Joint are carbon fiber/epoxy composites with a tensile modulus of 70 GPa.…”

“…Nevertheless, each bundle is completely dry, and no matrix is present inside. Therefore it is possible to conclude that macro-impregnation occurs, but no micro-impregnation [ 14 ].…”

Finite Element Modeling of Multiscale Diffusion in Intercalated Nanocomposites

“…The dual scale diffusion problem is similar to the problem of polymer flow during fiber impregnation in infusion processes used in composite materials fabrication. In this case, two mechanisms of impregnation have been clearly identified: the first one, occurring at lower time scales, characterized by a higher value of permeability, as defined by the Darcy law, is associated with interbundle flow, whereas the second one, occurring at higher time scale, and therefore characterized by a lower value of permeability, is associated with intrabundle flow [19]. The first mechanism involves flow of the molten polymer between fiber bundles (macroimpregnation), whereas the second one involves polymer flow inside each bundle (microimpregnation).…”

High strength injection molded thermoplastic composites

“…2 that show the measured viscosity on the selected materials. It has been demonstrated by several authors that in these conditions, fluids can be considered Newtonian fluids with little error [13][14][15][16].…”