汽车保险杠树脂传递模塑成型试验研究

采用理论分析和试验研究相结合的研究方法,解决了汽车保险杠树脂传递模塑成型工艺问题.研究结果表明:注射压力较小树脂充模时间变化较为显著;较低的树脂粘度可以显著提高充模效率,但粘度过低会造成纤维束间流动速度远大于纤维束内流动速度,导致气泡不易排除而引发制件内部各种缺陷.     

植物纤维真空模压成型设备控温装置的设计

为使植物纤维真空模压成型过程中树脂流动处于最佳工艺状态,在传统成型设备的基础上增加自动控温装置。该装置由DS182B20温度传感器实时采集模具温度数据,利用STC89C51单片机控制模具温度恒定,从而使充模过程中树脂受热粘度降低,加快在纤维束间的流动,缩短充模时间,提高成型效率。     

微壳体塑件充模流动三维数值模拟

针对微注塑成形中熔体充模流动行为,运用流体分析软件Fluent,对微壳体塑件熔体充模流动进行了三维稳态模拟。建立了微观黏度模型和壁面滑移模型,运用VOF多相流模型,研究了熔体充满型腔时的稳态三维流场,做出切片图分析了压力场和速度场。通过对考虑和不考虑微尺度影响(微观黏度和壁面滑移)的对比和分析,可以看到考虑微尺度因素影响时充模阻力减小约19%,而速度变化不明显。分析表明微尺度黏度对熔体流动影响显著,有利于微注塑熔体充模,而壁面滑移对充模流动影响较小。     

真空导入树脂模塑工艺对EKB1100/430LV复合材料纤维含量及力学性能的影响

通过真空导入树脂模塑工艺制备了EKB1100/430LV复合材料,研究了不同工艺参数对复合材料中玻璃纤维含量及力学性能的影响。结果表明:纤维含量随真空度的增大而增加,靠近树脂注入口区域的纤维含量较低,而真空抽口附近的纤维含量最高;复合材料的拉伸强度和压缩强度也随真空度的增大而增大;充模前对预成型体实施压缩可提高纤维含量;充模过程中溢流一定的树脂可提高弯曲强度和层间剪切强度。     

自动压力凝胶工艺充模过程的三维非等温数值模拟

应用基于控制体积的有限元法（CV／FEM）建立了自动压力凝胶工艺（APG）充模过程的全三维非等温数值模拟模型。并采用透明窗DgnCCD摄像机采集充模过程中树脂流动前沿的图像,与数值模拟结果进行对比验证。对比分析结果显示,在不同的边界条件和不同的充模时刻,数值模拟预测的流动前沿基本上与实验观测所得流动前沿一致。     

薄壁气体辅助注塑件气体穿透过程的研究

基于气体穿透实验技术的研究分析，针对气体辅助注射成形中气体穿透气道的复杂过程，对薄壁气辅注塑件沿圆形截面气道穿透推进并形成模壁表层熔体的充模流动过程进行了研究。通过引入合理的简化和假设，建立了反映充模流动压力梯度、材料性能、表层熔体厚度比、非牛顿指数等影响因素的计算穿透速度和时间的数学方程．对气体注射压力、熔体温度、非牛顿指数影响气体穿透充模过程进行了实例数值模拟研究。结果表明，增大气体注射压力，其气体穿透方向所形成的表层熔体厚度比值也增大，降低熔体注射温度和非牛顿指数会增大气体穿透的壁厚值，其值接近国外试验测定值，也比较符合实际的气辅注射成形工艺结果。     

DPVC工艺充模过程数值模拟和实验研究

为探究真空差压注型工艺(Differential Pressure Vacuum Casting,DPVC)中充模阶段充模速度及充模压差对薄壁产品质量的影响。采用一种基于SIMPLEC-VOF法的液-气两相耦合数学模型,对DPVC充模过程的流动形态进行了分析;并进行了相应的充模实验,数值模拟和实验结果表明:充模薄壁类产品(壁厚3mm内),注型材料黏性力占据了主导地位,扰动得到了有效抑制,流动是稳定的,差压充模过程卷气现象较少,但排气穴位置、数量对产品气穴缺陷影响较大,合理设置可基本消除注件内的气泡缺陷。     

注射成型聚合物充模取向应力场模型化理论研究:恒温不可压缩熔体

研究复杂流场条件下恒温不可压缩聚合物熔体注射充模流动诱导取向应力场数学模型理论。针对聚合物缠结大分子链单体在成型充模过程中的无轨形变特性,基于珠簧链模型与统计力学理论,建立以缠结大分子链单体等效末端距矢量(End-to-end vector,ETEV)为核心的恒温不可压缩聚合物充模流动诱导取向物理模型;由不可逆热力学与连续介质力学理论出发,研究得出与胡克定律具有类似形式的缠结大分子链单体流动诱导形变线弹性理论模型,进而得出恒温不可压缩聚合物充模流动诱导应力场线弹性模型;研究聚合物充模流动诱导取向的高弹形变特性,推导得到理论上等价、且具有更高解析精度的恒温不可压缩聚合物充模流动诱导取向应力场高弹性形变模型;引入八链朗之万模型以表征缠结大分子链单体相关参量与微元体积之间的定量关系,得出模型的解析形式;研究相关模型的结构特点及物理性态,比较各模型在表征聚合物充模流动诱导应力-应变工程问题的适配性及其关联性。     

全三维注塑成形流动模拟有限元模型的研究

注塑制品往往具有复杂的几何形状，存在着壁厚的差异。三维流动模型比二维模型能更准确地模拟出熔体充模流动的情况。提出了一种基于全三维模型的注塑成形流动模拟的数学模型和数值实现方法，把速度和压力同次插值的方法成功地应用到三维注塑模拟的计算中，采用三维控制体积追踪塑料熔体的流动前沿，在温度场计算中，全面考虑了对流项在各个方向的影响，使模型的适用范围更广，结果更准确。在此基础上开发了相应的软件，可以计算熔体充模过程中的压力场、速度场和温度场等。实验验证和算例分析说明了三维流动模型的有效性。     

注射填充过程的计算机模拟

以Hele-Shaw 流动为基础,建立了塑料熔体充模流动的数学模型。采用MOLDFLOW 充模模块,对轿车发电机散热罩的充模流动过程进行了动态模拟。分析并解决了影响制品质量的主要原因和问题。     

General method for predicting the sand erosion rate of GFRP

Sand erosion behavior and wear mechanism of various types of glass fibre reinforced plastics (GFRP) were investigated. Erosion behavior of fibre reinforced plastics (FRP) changed from ductile manner to brittle one with increase of glass fibre content, and erosion rate was maximum at vertical impact for higher glass fibre content FRP. FRP showed higher resistance to erosion damage than resin matrix at low angle of attack, the contrary tendency can be observed at higher angle of attack. The importance of damage of glass fibre bundles accompany with surrounding resin and effect of orientation angle of fibres on erosion damage of FRP were pointed out. Based on these factors and applying similar equation of the rule of mixture for strength of FRP, prediction method for erosion rate was proposed.By using this method, erosion rates of all types of GFRP under various angles of attack and impacting velocity can be estimated by knowing only the rate of matrix resin.     

树脂超声处理的新型涂层技术研究

为提高快速成形系统中堆积方向的制作分辨率,研究了光敏树脂的黏度、表面张力及固液两相接触角随超声处理时间和功率的变化规律。试验结果表明:LPR2001型光敏树脂在超声处理开始的2~5min,树脂的黏度、表面张力及接触角迅速减小;随处理时间延长,以上树脂特性值随之回升;超声功率在40~50W时,树脂的黏度、表面张力及接触角减小幅度最大。对光敏树脂超声处理前后能实现的最小涂层厚度进行了实验对比,结果表明:超声处理的树脂能将最小涂层厚度由原来的0.02mm降低到0.01mm。     

Fibre/resin interaction in fragmentation tests: coaxial vs. simple specimens comparison

Fragmentation tests of single carbon fibres embedded in small resin specimens are widely used to compare fibre surface treatments or sizes. A limitation of the test is that the matrix must have a high enough ultimate strain for the multiple fracture process to be fully achieved before specimen fractures. The so-called coaxial geometry was introduced in order to extend the method to low strain-to-failure resin systems. In agreement with the Cox theory of the elastic stress transfer, interposition of a 'high'-modulus material between the fibre and the resin (the 'low'-modulus material) results in a shorter fragment length, i.e. a better stress transfer.     

多型腔注射模充填不平衡试验

多型腔注射模在实际生产中有着广泛应用,充填平衡是保证多型腔模塑制品质量均匀一致的关键。自然平衡流道中也会发生充填不平衡现象,其原因可能是熔体流动产生的剪切热所致,但一直没有试验结果予以证明。基于此,利用可视化注射模具和红外温度传感器,通过直接观测熔体在流道和型腔中的动态流动行为并测量型腔入口处熔体的温度变化,对不同注射速率下不同材料在自然平衡多型腔注射模的充填不平衡进行研究。结果表明,由于剪切热的作用,主流道中不均匀但对称的熔体温度分布在分流道中失去对称性是产生充填不平衡的根本原因;充填不平衡程度不但取决于主流道中熔体的温度分布,还取决于分流道中凝固层的分布及熔体粘度对温度变化的敏感性。解决自然平衡多型腔注射模充填不平衡问题的根本,在于改善或消除分流道中熔体温度分布在流动平面的不对称性。     

Role of polymeric matrices in improving wear resistance of irradiated FRP composites

The present paper reports the effect of different resin matrices on the abrasive wear behaviour of woven fabric composites based on them. Three different resin systems and a common glass fibre reinforcement were used in the present study. It was found that polymer composites based on the epoxy resin system show maximum wear resistance. This has been attributed to the fact that fibre-matrix interfacial bonding is very strong between the glass fibres and epoxide resin. The bonding resists composite failure and improves on irradiation.     

A study on radial spreading of a resin droplet with varying viscosity under UV curing process

One-dimensional axisymmetric fluid dynamics of a resin droplet was studied when it is squeezed between two parallel plates under the influence of UV (Ultraviolet) radiation curing. The radial spreading of different level of resin viscosity and its spreading speed are developed from the previous framework for viscous fluid dynamics of Newtonian fluid with negligible capillary number and Reynolds number. Then the final equations for spreading radius and spreading speed under the influence of UV curing are related with each other for the given spreading radius, viscosity at the corresponding elapsed time. The elapsed time increment could be assessed from the incremental elapsed time calculated from the incremental radius, assuming negligible viscosity change when the incremental radius is controlled to be small enough. The spreading of resin droplet is highly restricted by rapid viscosity rise due to crosslinking polymerization from UV curing. The theory was verified through droplet spreading tests with resin samples of different initial viscosities and of the same viscosity under different UV power. The theoretical prediction was in good agreement with the experimental results for both spreading radius and spreading speed. The same theoretical approach was then applied to the prediction of spreading boundary size and time to reach to it for a slow curing resin with different UV power intensity.     

Ultrasonic torsional guided wave sensor for flow front monitoring inside molds

Measuring the extent of flow of viscous fluids inside opaque molds has been a very important parameter in determining the quality of products in the manufacturing process such as injection molding and resin transfer molding. Hence, in this article, an ultrasonic torsional guided wave sensor has been discussed for monitoring the movement of flow front during filling of resins in opaque molds. A pair of piezoelectric normal shear transducers were used for generating and receiving the fundamental ultrasonic torsional guided wave mode in thin copper wires. The torsional mode was excited at one end of the wire, while the flowing viscous fluid progressively wet the other free end of the wire. The time of flight of the transient reflections of this fundamental mode from the air-fluid interface, where the wire enters the resin, was used to measure the position of the fluid flow front. Experiments were conducted on four fluids with different viscosity values. Two postprocessing algorithms were developed for enhancing the transient reflected signal and for suppressing the unwanted stationary signals. The algorithms were tested for cases where the reflected signals showed a poor signal to noise ratio.     

SiO2包裹纳米Cu粒子/环氧树脂复合材料及其在芯片封装领域的应用

为提高微电子封装材料的散热性能并保留其良好的电绝缘性能,以环氧树脂为基体,二氧化硅包裹纳米铜粒子(SiO2-Cu)为填料,采用机械混炼法制备了芯片封装用SiO2-Cu环氧树脂复合材料。采用SEM和TEM研究了SiO2-Cu纳米粒子在环氧树脂中的分散情况;研究了填料对复合材料导热系数、热膨胀系数(CTE)和力学性能的影响。结果表明:SiO2-Cu纳米粒子在环氧树脂中分散性良好;复合材料的导热系数随SiO2-Cu纳米粒子填充量的增加而增大,填充量(体积分数)超过25%时导热系数开始下降,SiO2-Cu纳米粒子适宜用量为总体积的25%;随着填料的增加,复合材料的CTE减小;当SiO2-Cu纳米粒子填充量为25%时,用于芯片封装材料时具有良好的抗冲击性能和较长的电迁移失效时间。     

树脂药卷自动生产线系统设计

针对目前树脂药卷的生产多采用人工配比称重,然后进行人工封装结扎,工人劳动强度大,生产效率低。该论文研究的树脂药卷自动生产线采用了PID控制技术,精确控制输送速度及各生产原料的比例成分,运用人机学理念来实现产品的自动填充、结扎,大大提高了生产效率,降低了工人的劳动强度。