Assessment of the relevance of sintering in thermoplastic commingled yarn consolidation

Abstract

The aim of the present article is to study the different phenomena which are at the basis of the consolidation of commingled thermoplastic semi‐pregs made of amorphous polyester fibers and E‐glass reinforcement. The evolution of the void fraction during the consolidation of the composite was monitored by a dynamometer, equipped with parallel plates and a forced convection oven. Different physical changes were associated to the consolidation temperature. Scanning electron microscopy (SEM) and thermomecahnical analysis (TMA) showed that at low temperature, matrix fiber deformation and sintering are responsible of the initial void reduction. At a temperature higher than the onset of the flow region, reinforcement impregnation is responsible of the further void reduction. Dimensionless analysis confirmed that at lower temperatures, corresponding to higher viscosities, consolidation due to viscous flow of the polymer matrix is negligible compared to consolidation due to sintering of matrix fibers. The results indicate that the Darcy law can efficiently represent the consolidation during the microscale impregnation of the reinforcement, but cannot account for the initial stages of consolidation. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Commingled Yarn Spinning for Thermoplastic/Glass Fiber Composites

“…Above 180 °C, the glass fibers are wetted out by matrix which flows from the resin-rich pools into the glass fiber bundles. These findings go along with more recent literature results which try to explain commingled yarn consolidation via a sintering approach [32] rather than by Darcy's law. It is still open for discussion what really happens in the temperature region until 180 • C. The glass transition temperature of the PP matrix is somewhat in the region of −5 • C. Melting of the crystalline areas occurs between 155 and 170 • C. As a consequence, the viscosity of the PP drops within the melting area by almost 3 decades, as reported in Figure 9.…”

“…Above 180 • C, the glass fibers are wetted out by matrix which flows from the resin-rich pools into the glass fiber bundles. These findings go along with more recent literature results which try to explain commingled yarn consolidation via a sintering approach [32] rather than by Darcy's law.…”

Development and Characterization of Amorphous Thermoplastic Matrix Graphene Nanocomposites

“…Themomechanical Analysis (TMA) was performed on GIC powders heating 3 mg samples between 25 and 450 °C at different heating rates and using different compression forces on the sample. Details on the the TMA experiment for powder characterization are reported elsewhere [ 5 , 47 , 48 , 49 ].…”

Experimental measurement of transversal micro‐ and macro permeability during compression molding of PP/Glass composites

“…Macro‐impregnation occurs when the matrix flows between bundles or yarns, and involves elimination of large‐scale dry spots. Micro‐impregnation is associated with the matrix flow inside each bundle, around individual fibers, and affects micro‐porosity and the fiber–matrix interface bonding .…”