Simulation of thermoplastic composites
Thermoplastic composites are gaining increasing popularity as a construction material in a modern industry. An essential feature of such materials is the ability to change its phase, turning into a viscous, near liquid state under high temperatures. All manufacturing processes of fabricating complex shaped components of thermoplastic materials involve heating and subsequent cooling of such materials. However, from a technology point of view, there is problem of warpage and deformations of structure occurring during phase transitions, accompanied by defects origination. Manufacturing experiments may be quite expensive and do not ensure required quality of final material. This necessitates the search for new methods allowing engineer to simulate manufacturing processes and the effects of temperature cycle on thermoplastic polymer. From a mathematical model point of view the main aspects are the changes in degree of crystallinity of material and related changes in mechanical characteristics, and additional chemical shrinkage. Therefore, material models to be developed shall account for following phenomena, depending on the phase state of material:
- growth of degree of crystallinity;
- changes in stiffness characteristics;
- changes in temperature properties;
- changes in strength properties of material.
Crystallization kinetics features a relatively well developed and, by all appearances, settled theoretical description [1–6]. Mechanical parameters of thermoplastic polymers can be found in various publications [1, 4, 5, 7]. The least developed area is a modeling of strength characteristics of such materials. Some attempts at evaluation of strength characteristics are described in [8–10]. In the present work a possible approach to modeling the influence of process temperatures on thermoplastic composites and evaluating residual stresses and strength characteristics is proposed.