纤维增强注塑熔接线强度预测模型与实验研究

Prediction model and experimental study of weld line strength in fiber reinforced injection molding

熔接线是影响注塑制品强度的关键因素之一,而目前以汇合角预测熔接线强度的力学模型并没有体现注塑工艺的影响。为了科学定量地认识熔接线区域强度的变化规律,准确预测熔接线力学性能,首先对带扇形孔的制品进行注塑模拟分析,研究了注塑温度、注射速率以及保压压力对熔接线汇合角的影响,结果显示注塑温度、保压压力不是通过改变熔体前沿汇合角来影响熔接线强度。基于此,为全面体现注塑工艺、汇合角对熔接线强度的影响,在现有模型基础上通过引入注塑工艺影响因子重新构造了体现注塑工艺、汇合角对熔接线区域强度影响的预测模型。设计并制造了用于成型扇形孔制品的注射模具,开展了不同工艺条件下30%长玻纤增强聚丙烯扇形孔制品注塑实验,根据实验结果推导出了体现注塑温度和保压压力影响的注塑工艺影响因子数学表达式,利用实验数据拟合确定了模型中的相关参数,并对模型进行了回归分析。结果表明,新构建的强度预测模型可以准确计算不同注塑温度、保压压力下熔接线不同位置的强度。

The weld line is a crucial factor influencing the strength of injection molding products.However,the current mechanical model that predicts weld line strength based on converging angle fails to consider the impact of the injection molding process.In order to scientifically and quantitatively understand the variation law of the regional strength of the fuse connection and accurately predict the mechanical properties of the fuse connection,injection molding simulation analysis on the products with fan-shaped holes was firstly carried out,and the effects of injection molding temperature,injection rate and holding pressure on the converging angle of fusion line were studied.The results show that the injection molding temperature and holding pressure do not affect fusion line strength by changing the melt front converging angle.Based on this,in order to comprehensively reflect the influence of injection molding process and converging angle on weld line strength,the prediction model reflecting the influence of injection molding process and converging angle on weld line strength was reconstructed by introducing injection molding process influence factor.By designing and manufacturing an injection mold for molding fan-hole products,injection molding experiments of 30wt%long glass-fiber reinforced polypropylene fan-shaped hole products under different technological conditions were carried out.Based on the experimental results,the mathematical expression of the injection molding process influence factor reflecting the effects of injection temperature and holding pressure was derived,the relevant parameters in the model through data fitting were determined.The regression analysis of weld line strength prediction model shows that the strength model established can accurately predict the tensile strength of weld line at different positions under different injection molding conditions.