Rheological Modeling for Production of High Quality Polymeric
The fundamental defect inherent to the thermoforming technology is wall-thickness variation of the products due to inadequate thermal processing during production of polymer. A nonlinear viscoelastic rheological model is implemented for developing the process model. This model describes deformation process of a sheet in thermoforming process. Because of relaxation pause after plug-assist stage and also implementation of two stage thermoforming process have minor wall-thickness variation and consequently better mechanical properties of polymeric articles. For model validation, a comparative analysis of the theoretical and experimental data is presented. Keywords—High-quality polymeric article, Thermal Processing, Rheological model, Minor wall-thickness variation.
Simulation of Thermoforming and Blowmolding — Theory and Experiments
The increased use of polymers in the fabrication of various products ranging from beverage bottles, automotive fuel tanks, food trays, to refrigerator liners has made it important that minimum requirements on part thicknesses be met when forming plastic parts. The two primary industrial processes for forming both small and large, thin walled plastic parts are thermoforming and blowmolding. Generally, during these processes, polymers behave in a viscoelastic manner and their deformation process involves large deformations, large strains, large strain rates, contact between the hot polymer and the mold wall, and physical instabilities may also occur during inflation. However, in thermoforming and blowmolding, especially when plug assisted, the process occurs rapidly and at a strain rate high enough for the elastic effects to be dominant and there is no time for viscous dissipation. The polymer undergoes a large elastic deformation.
A New Vacuum Pressure Infiltration CFRP Method and Preparation Experimental Study of Composite
In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 °C, vacuum heating curing at –0.05 MPa + 30 min + 80 °C, and hot-press curing at 0.7 MPa + 5 min + 50 °C, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.