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It is proposed that an impregnation model can predict the porosity of composites for power-law fluids impregnation in fabric. The impregnation model takes the material properties and fabric characteristic dimensions into account. In order to verify the model, glass fabric reinforced polypropylene (PP) composites are fabricated by using compression molding procedure. The impregnation model is validated by a series of comprehensive experiments, and the experimental results are perfectly consistent with the impregnation model’s value. The impregnation process is studied respectively through the model and the experiment. The results of it have shown that the impregnation time can indeed be shortened for compression molding procedure by increasing the processing temperature or increasing the applied pressure.

© 2016, Springer Science+Business Media Dordrecht. Through the combination of Reynolds equation and Darcy’s law, a mathematical model was established to calculate the pressure distribution in wedge area, which contributed to the forecast effect of processing parameters on impregnation degree of the fiber bundle. The experiments were conducted to verify the capacity of the proposed model with satisfactory results, which means that the model is effective in predicting the influence of processing parameters on impregnation. From the mathematical model, it was known that the impregnation degree of the fiber bundle would be improved by increasing the processing temperature, number and radius of pins, or decreasing the pulling speed and the center distance of pins, which provided a possible solution to the difficulty of melt with high viscosity in melt impregnation and optimization of impregnation processing.

© 2016, Springer Science+Business Media Dordrecht. The effect of process variables such as roving pulling speed, melt temperature and number of pins on the fiber fracture during the processing of thermoplastic based composites was investigated in this study. The melt impregnation was used in this process of continuous glass fiber reinforced thermoplastic composites. Previous investigators have suggested a variety of models for melt impregnation, while comparatively little effort has been spent on modeling the fiber fracture caused by the viscous resin. Herein, a mathematical model was developed for impregnation process to predict the fiber fracture rate and describe the experimental results with the Weibull intensity distribution function. The optimal parameters of this process were obtained by orthogonal experiment. The results suggest that the fiber fracture is caused by viscous shear stress on fiber bundle in melt impregnation mold when pulling the fiber bundle.

© SAGE Publications. The fiber pre-spreading is of great importance when the continuous fiber-reinforced thermoplastic composites are produced by the melt impregnation process. In this paper, an improved spreading device is introduced, in which via grooving the pins for the airflow, the fiber is pre-spread by the combination of the airflow and the rolls. The objective of this operation is to reduce the contact friction between the fiber bundle and the pins surface, thereby reducing fiber fracture during the pre-spreading process. The influence of airflow on the pre-spreading of the fiber bundle is also investigated in this paper. It is found that the effect of airflow on the impregnation is significant and the fiber fracture rate is reduced effectively by analyzing the water absorption rate, interlayer shear strength and fiber fracture rate of the prepreg. When the air pressure is 0.2 MPa, the performance of the prepreg is optimal.

Bulge forming (BF) processes as a metal working operation has received comprehensive investigation. The process and its products have been widely used in many areas. However, there are few papers published to deal with plastic BF (the application of BF technique to polymer processing, PBF). Compared to conventional polymer processing such as extrusion, injection moulding and blow moulding processes, the PBF process is relatively new, and therefore, there is no extensive knowledge base for tool and process design. This paper reviews the progress and features of the BF process and discusses the feasibility and necessity of PBF. In addition, the relationship between process variables and achievable part geometry and mechanical performance are investigated.