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.
Assessment of the relevance of sintering in thermoplastic commingled yarn consolidation
GRECO, Antonio;MAFFEZZOLI, Alfonso
2011-01-01
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
