Vacuum-bag-only processing of composites

Unrestricted Ultrasonic imaging in the C-scan mode in conjunction with the amplitude of the reflected signal was used to measure flow rates of an epoxy resin film penetrating through the thickness of single layers of woven carbon fabric. Assemblies, comprised of a single layer of fabric and film, were vacuum-bagged and ultrasonically scanned in a water tank during impregnation at 50°C, 60°C, 70°C, and 80°C. Measured flow rates were plotted versus inverse viscosity to determine the permeability in the thin film, non-saturated system. The results demonstrated that ultrasonic imaging in the C-scan mode is an effective method of measuring z-direction resin flow through a single layer of fabric. The permeability values determined in this work were consistent with permeability values reported in the literature. Capillary flow was not observed at the temperatures and times required for pressurized flow to occur. The flow rate at 65°C was predicted from the linear plot of flow rate versus inverse viscosity.; The effects of fabric architecture on through-thickness flow rates during impregnation of an epoxy resin film were measured by ultrasonic imaging. Multilayered laminates comprised of woven carbon fabrics and epoxy films (prepregs) were fabricated by vacuum-bagging. Ultrasonic imaging was performed in a heated water tank (65°C) during impregnation. Impregnation rates showed a strong dependence on fabric architecture, despite similar areal densities. Impregnation rates are directly affected by inter-tow spacing and tow nesting, which depend on fabric architecture, and are indirectly affected by areal densities.; A new method of predicting resin infusion rates in prepreg and resin film infusion processes was proposed. The Stokes equation was used to derive an equation to predict the impregnation rate of laminates as a function of fabric architecture. Flow rate data previously measured by ultrasound was analyzed with the new equation and the Kozeny-Carman equation. A fiber interaction parameter was determined as a function of fabric architecture. The derived equation is straight-forward to use, unlike the Kozeny-Carman equation. The results demonstrated that the newly derived equation can be used to predict the resin infusion rate of multilayer laminates.

采用结合反射信号幅度的C扫描模式（C-scan mode）超声成像（Ultrasonic imaging）技术，测量环氧树脂膜（epoxy resin film）沿单层机织碳纤维布（woven carbon fabric）厚度方向的渗透流速。由单层织物与薄膜组成的组装件经真空袋封装后，于50℃、60℃、70℃及80℃的浸渍过程中在水槽内开展超声扫描。将测得的流速与粘度倒数作图，以确定该薄膜非饱和体系的渗透率。结果表明，C扫描模式超声成像是测量单层织物内树脂沿厚度方向流动的有效手段。本研究测得的渗透率数值与文献报道结果一致。在加压流动所需的温度与时长条件下未观测到毛细流动。基于流速与粘度倒数的线性关系，可预测65℃下的流动速率。

采用超声成像法测量了环氧树脂膜浸渍过程中织物结构对厚度方向流动速率的影响。通过真空袋封装工艺制备了由机织碳纤维布与环氧树脂膜（预浸料（prepregs））组成的多层层合板。浸渍过程中在控温水槽（65℃）内开展超声成像测试。尽管面密度相近，浸渍速率仍显著依赖于织物结构。浸渍速率直接受依赖于织物结构的纱束间距与纱束嵌套情况影响，并间接受面密度影响。

提出了一种预测预浸料与树脂膜浸渍工艺中树脂浸渍速率的新方法。基于斯托克斯（Stokes）方程推导得到可预测层合板浸渍速率的方程，该速率为织物结构的函数。采用新方程与科泽尼-卡曼（Kozeny-Carman）方程对已有的超声测得的流速数据进行分析。得到了作为织物结构函数的纤维相互作用参数。与科泽尼-卡曼方程不同，该推导得到的方程使用简便直观。结果表明，新推导的方程可用于预测多层层合板的树脂浸渍速率。