Thermoplastic pultrusion process: Modeling and optimal conditions for fibers impregnation

Abstract

Pultrusion is a crucial method for continuous production of fiber-reinforced composites. It was developed several years ago for thermosetting polymer matrices, but the challenge is now to extend it to thermoplastic matrices, with a much higher viscosity. In this paper, we propose an analysis of the parameters influencing fiber impregnation in the conditions of this process. A semi-analytical one-dimensional axisymmetric model based on Darcy’s law and Stokes equations is developed to predict the impregnation profile inside the fibrous phase in the case of a natural impregnation governed by capillary forces. Thanks to a dimensional analysis, it enables to quantify the influence of all the material and testing parameters under the assumption of a slow variation of the geometry of the impregnation die. The cases of a straight and conical dies are discussed. For the first case, an exhaustive numerical study enables to define the optimal processing conditions for a perfect impregnation. Those results are shown to be useful tools for finding an optimal pulling velocity and die length for a given fluid/fibers pair. For the second case, we show that section reductions do not improve impregnation.

Experimental study of roving configuration’s influence on the flow field in a full-scale transparent pultrusion injection box

“…Koubaa et al developed a set of coupled differential equations based on a 1D flow model to investigate the impregnation behavior of (tubular) textiles pulled through a (tapered) tube with thermoplastic resins and analyzed derived dimensionless parameters regarding viability of continuous profile production with polymerized thermoplastics. 11…”

Effect of pneumatic spreading on impregnation and fiber fracture of continuous fiber-reinforced thermoplastic composites

“…Continuous fiber-reinforced thermoplastic resin matrix composites are mainly produced by melt impregnation method, solution impregnation method, in situ polymerization method, powder impregnation method, mixed yarn method and film laminating method. [10][11][12][13][14][15][16][17][18] The process of melt impregnation is simple, environmentally friendly, and convenient to achieve the industrialization. Consequently, it has been one of the most commonly used methods to produce the thermoplastic prepreg.…”

Thermoplastic Pultrusion: A Review

“…Koubaa et al [ 279 , 280 ] have developed a pultrusion impregnation model based on the Navier–Stokes equation, having the following expression in a cylindrical coordinate system: where —coordinate axis coinciding with the pulling direction and —fluid motion speed along the longitudinal axis. The following boundary conditions are imposed: zero component of fluid motion speed outside fibers, and equality of fluid motion speed inside fibers and of the pulling speed.…”