GMT压缩模塑过程中模腔内的传热行为

分析压缩模塑法生产GMT制品过程中模腔内的传热行为，对制品内部非稳态传热过程进行实验研究和数学模拟，计算结果与实验结果基本吻合；探索制品冷却速率对其结晶度及弯曲强度的影响，研究了适宜的模温及冷却速率。

Heat Transfer Behavior of GMT in Mould Cavity during Compression Molding

It is well known that the mechanical properties of thermoplastic composite parts depend upon processing parameters such as cooling rate, mold temperature, fiber content, and residence time in mold. In our work, heat transfer in the cavity of mold in compression molding of GMT was studied, focused on one-dimension heat conduct in the direction of thickness in the interior of GMT parts. Variations of temperature inside the parts with cooling time and conditions were measured and recorded by using a kind of special thermocouples buried in the middle of parts during layout of preheated blanks. Temperature distribution in the plane of the parts was nearly uniform. The gradient of temperature in plane varied with cooling process, and the biggest difference of temperature was only 3°C. The experimental results showed that the crystallinity of polypropylene and the flexural strength of the parts strongly depended on the molding parameters. The effects of mold temperature and the part thickness on cooling and crystallization processes were notable, but fiber content in GMT sheets had little effect on heat transfer in mold. The proper mold temperature should be about 80°C, and the mean crystallinity of the resin should be controlled in the range of 0.51～0.55. The surfaces of parts were improved, and the shrinkage was reduced. The mean cooling rate in mold should be controlled about 1.0～1.1°C/s, and flexural strength attained was 124MPa. Based on the experimental results, a mathematical model of one-dimension heat conduct of the part in the cavity was established to simulate the process, and the simulated results agreed well with the experimental data.