Moisture diffusion in polyamide 6,6 (PA66) and its short glass fiber-reinforced composites has a great influence on their mechanical properties and service lives under hydrothermal environments. Hence, the moisture diffusion in neat PA66 and its composites was studied comprehensively in this study with the general Fickian model. To systematically investigate the effects of the fiber content, humidity, temperature, and humidity–temperature coupling effect on the diffusion coefficient and equilibrium concentration, gravimetric experiments for the PA66 composites were carried out under different hydrothermal conditions. The results show that the equilibrium moisture concentration depended on the relative humidity and fiber content but only depended weakly on temperature. The diffusion velocity was affected by the three aforementioned factors with different trends. The analysis of variance demonstrated that the humidity–temperature coupling effect played an important role in the diffusion process. The regression analysis gave the corresponding quadratic regression equations. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42369.

Numerical prediction of morphology in polymer blends during injection molding is of vital importance for mastering the material microstructure and optimizing the property of molded parts, in which modeling the morphological evolution in processing is the premise. The principle and crucial factors of the deformation of dispersed phases have been investigated in this paper, followed by introducing six deformation models (MM, JT, YB, affine model, shear model, and Cox models) systematically. Simulation results of these models under five typical flows (steady deformation in simple shear flow, transient deformation in simple shear flow, relaxation after step shearing, shearing reversion, and droplet broadening) are compared and evaluated. It shows that the MM model can be chosen for modeling the steady deformation or small deformation process in the injection molding, and the affine model is highly feasible for the transient large deformation in the high shearing process of injection molding. Finally, the selected models are used in the injection molding simulation for verification.

A challenging task in injection molding industry is to minimize shrinkage and warpage (S&W) through optimal setting of molding conditions. In determining the relationship between molding conditions and product dimension, most existing literature considered S&W as a whole entity or focused on only one of them. The intention of this study was to distinguish these two terms, and perform a thorough analysis on the effect of operative conditions on S&W during injection molding process through a combination of experimental and numerical methods. Six process parameters with five levels were examined on a box-shaped product, and the single factor analysis of variance (ANOVA) was adopted in identifying the significance of each variable in the experiment. Results indicated that the effect of processing conditions on shrinkage is different from that on warpage. Specifically, packing pressure affects shrinkage most while packing time is the dominant factor in determining warpage. The reaction of shrinkage to packing pressure is monotonic, whereas the plot of warpage shows a U-shaped variation. A differential treatment of S&W can therefore help to enhance product quality. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The mid-plane model for warpage simulation of injection-molded parts requires a mid-plane mesh whose transformation is considerably time consuming. To overcome this drawback, a surface model-based warpage simulation is presented, in which the part is represented as a perfect bonding of two half-thickness plates with their reference surfaces at the outer boundary of the part. The plates over the surface mesh are modeled as flat shell elements, and a new triangular flat shell element is developed which combines an Assumed Natural DEviatoric Strain (ANDES) based membrane component and a Refined Nonconforming Element Method (RNEM) based bending component. The bonding is accomplished by multipoint constraints and a Lagrange multiplier based elimination method is proposed for constraint application. The results show that compared with some popular shell elements, ANSYS, Moldflow and the experiments, the presented model exhibits a high performance in computation accuracy. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

The proposed real-time intelligent model for the injection molding process control consists of the initial parameters setting and online defects correction. First, preliminary optimization based on a simplified simulation model is used for the initial setting. This simplified model adopts a geometric approximation of the original part by a rectangular edge-gated plate. Then, the molding trial will be run on the molding machine by using the initial process parameters. And a fuzzy inference model based on expert knowledge is developed for correcting defects during the molding trial. This defects correction procedure will be repeated until the part quality is found satisfactory. A corresponding intelligent system has been developed that is integrated with the injection machine by communicating with the controller. The system can be used to optimize process parameters real time. Experimental studies have been carried out for verification. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers.