ABSTRACT:The purpose of this article is to review the research done in the field of mathematical modeling and optimization of the injection-molding (IM) process. Various papers related to the mathematical description of the filling, postfilling, and plasticating phases of the IM process were assessed, and some recent advances on the IM field are described. In addition, research devoted to the optimization of the IM process based on various techniques is also discussed. These optimization techniques include design of experiments, artificial neural networks, and evolutionary algorithms. The strengths and weaknesses of each approach were discussed. Finally, this paper also discusses the optimization research performed in the IM process regarding some of the specific features associated with the processes such as runner system and cooling channel configurations, process conditions, gate location, and cavity pressure balancing. C

The elastic response of vertically aligned-carbon nanotube/polydimethylsiloxane (A-CNT/PDMS) nanocomposites is presented in this study and related to the underlying aligned-CNT morphology. Multiwalled carbon nanotubes (MWCNTs) at 1% Vf are embedded in a flexible substrate of PDMS to create a flexible polymer nanocomposite (PNC). The PNC properties are evaluated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile mechanical tests, and the full linearly elastic constitutive relation is established for such a PNC. The results suggest that the CNTs retain the alignment after wetting and curing of PDMS. PDMS is significantly modified by the reinforcing aligned-CNT fibers, demonstrating non-isotropic (as opposed to the isotropic neat PDMS) elastic properties all different from PDMS (Young's modulus of 0.8 MPa), including an anisotropy ratio of 4.8 and increases in the modulus of A-CNT/PDMS over PDMS by more than 900% and 100%, in the CNT longitudinal and transverse directions, respectively. This study reports the first full constitutive relation that may be useful in modeling PNCs as composites or as elements of hierarchical nanoengineered composites, particularly PDMS-CNT PNCs are envisioned as elements in biomedical devices such as pressure transducers and energy harvesters.

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During the ejection phase of the injection moulding cycle the parts are mechanically forced to separate from the moulding surfaces, this aspect being more relevant with deep cores. The design of the ejection system depends on factors such as the draft angles, the surface finish, and the properties of the moulding material at the ejection temperature and the dimensioning of actuation devices (e.g., hydraulic or pneumatic cylinders). Knowledge of the friction properties of the mating metal and plastics surfaces is important to optimize the ejection system. The coefficient of friction at the ejection stage depends on the surface texture of the core and the temperature at ejection. This paper reviews recent research on the static coefficient of friction in moulding conditions. It also reviews results obtained with a prototype apparatus that reproduces the conditions occurring during the ejection phase.

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