Hudson Tyler B, Yuan Fuh-Gwo
Department of Mechanical and Aerospace Engineering, North Carolina State University, 911 Oval Drive-3306 EBIII, Campus Box 7910, Raleigh, NC 27695; National Institute of Aerospace, 100 Exploration Way, Hampton, VA 23666.
J Nondestruct Eval Diagn Progn Eng Syst. 2018 May;1(2). doi: 10.1115/1.4039230. Epub 2018 Feb 23.
An in-process cure monitoring technique based on "guided wave" concept for carbon fiber reinforced polymer (CFRP) composites was developed. Key parameters including physical properties (viscosity and degree of cure) and state transitions (gelation and vitrification) during the cure cycle were clearly identified experimentally from the amplitude and group velocity of guided waves, validated via the semi-empirical cure process modeling software RAVEN. Using the newly developed cure monitoring system, an array of high-temperature piezoelectric transducers acting as an actuator and sensors were employed to excite and sense guided wave signals, in terms of voltage, through unidirectional composite panels fabricated from Hexcel® IM7/8552 prepreg during cure in an oven. Average normalized peak voltage, which pertains to the wave amplitude, was selected as a metric to describe the guided waves phenomena throughout the entire cure cycle. During the transition from rubbery to glassy state, the group velocity of the guided waves was investigated for connection with degree of cure, T, and mechanical properties. This work demonstrated the feasibility of in-process cure monitoring and continued progress toward a closed-loop process control to maximize composite part quality and consistency.
开发了一种基于“导波”概念的用于碳纤维增强聚合物（CFRP）复合材料的过程中固化监测技术。通过导波的幅度和群速度，从实验上明确识别了固化周期中的关键参数，包括物理性质（粘度和固化程度）和状态转变（凝胶化和玻璃化），并通过半经验固化过程建模软件RAVEN进行了验证。使用新开发的固化监测系统，在烘箱中固化期间，采用一系列高温压电换能器作为激励器和传感器，通过由Hexcel® IM7/8552预浸料制成的单向复合材料板，以电压形式激发和感应导波信号。选择与波幅相关的平均归一化峰值电压作为描述整个固化周期中导波现象的指标。在从橡胶态转变为玻璃态的过程中，研究了导波的群速度与固化程度、T和机械性能之间的关系。这项工作证明了过程中固化监测的可行性，并朝着闭环过程控制不断取得进展，以最大限度地提高复合材料部件的质量和一致性。
