Formability analysis for enhancing forming parameters in AA8011/PP/AA1100 sandwich materials

The remarkable nonlinearity between the viscosity and temperature significantly reduces the extrusion formability of Nylon-66. The conventional extrusion methods, which obtain extrusion profiles with high precision through first extrusion and then sizing in calibrator, are unable to realize the extrusion of Nylon-66, especially for GF/Nylon-66 composite. In this paper, a one-step extrusion method, which realizes the fast sizing of extruded parts by taking advantages of the crystallization of GF/Nylon-66 melt, was proposed based on the viscosity change features and crystallization behavior of GF/Nylon-66 around its melting temperature (T _m). Thus, the sizing and cooling processes using standardized dies in conventional extrusion methods can be eliminated. In this study, the one-step extrusion process of GF/Nylon-66 was investigated from three aspects including the extrusion rheological performance, the equilibrium property of extrusion flow and crystallization sizing behavior, based on finite element simulations and experiments. The results revealed that the melt flow property can be improved by increasing temperature and shear rate. The rheological constitutive equation can precisely describe the rheological performance of materials under different temperatures and shear rates. Increasing melt temperature and screw speed will reduce the melt flow equilibrium. With the melt temperature at neck ring mold being the peak crystallizing temperature and screw speed being appropriate, an optimized dynamic balance among the melt flow property, the flow equilibrium performance and the crystallization sizing capability can be achieved. Thus, the extrusion molding of GF/Nylon-66 can be implemented via one-step extrusion. The method proposed can realize the extrusion molding of GF/Nylon-66 with improved efficiency and reduced cost.