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首页> 外文学位 >Identification of Impact Damage in Composite Laminates through Integrated Pulsed Phase Thermography and Embedded Thermal Sensors.
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Identification of Impact Damage in Composite Laminates through Integrated Pulsed Phase Thermography and Embedded Thermal Sensors.

机译：通过集成脉冲相热成像和嵌入式热传感器识别复合材料层压板的冲击损伤。

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摘要

This dissertation develops a methodology to identify impact damage in aerospace composite laminates using integrated pulsed phase thermography and fiber Bragg grating (FBG) sensors. Initially, a two-dimensional woven, carbon fiber epoxy laminate is used to calibrate the defect depth with blind frequency for the particular material system using pulsed phase thermography (PPT). The calibration specimen contains simulated defects in the form of polymer foam inclusions. The calibrated depth vs. blind frequency relation is then applied to specimens with barely visible impact damage due to low velocity impacts. The results demonstrate that the use of the polymer insert simulated defects, in contrast to drilled holes or inserts with higher thermal contrast, provides thermal phase shifts similar to that observed in the impacted specimens. Despite the differences between the simulated and impact damage (e.g. the irregular boundaries and thin nature of the delaminations), the minimum depth of delamination from the impacted surface and the extent of damage on the rear surface of the specimen calculated from the PPT images are shown to correspond well with those of visual observations.;The next group of laminated composite specimens are fabricated with embedded FBG sensors to test the ability of the combined inspection method using pulsed phase thermography and FBG sensors to identify impact damage severity. Initially three sets of specimens containing a single FBG sensor at the mid-plane, along with data from previous studies, are used to optimize the distance of low velocity impact damage from the FBG sensor and also to optimize the FBG interrogator data acquisition rate. The results from these specimens show a wide scatter in the FBG sensor temperature measurements during cooling. Also, due to its low conductivity, specimen took long time to cool, increasing the inspection time. Therefore for the final specimen the FBG sensor data acquisition is performed in the heating transient. The final specimen contains three FBG sensors, embedded at different depths and is used to quantify the initiation and through the thickness progression of impact damage of varying severities. Pulsed phase thermography is used for the global assessment of the impact damage, meaning to quantify the absolute damage size and also to quantify the damage severity in terms of the phase contrast between damaged and pristine specimen areas. The results demonstrate the higher sensitivity of the internal FBG temperature sensors than that of the PPT during damage initiation. The PPT images were able to capture the later during damage progression. Visual inspection, microscopic images and PPT results are used to compare the damage modes and severity at different depths detected by the FBG sensors. A damage assessment model is then formulated based on the results of combined inspection method.
机译：本文提出了一种利用集成脉冲相位热成像和光纤布拉格光栅（FBG）传感器识别航空复合材料层压板冲击损伤的方法。最初，对于特定的材料系统，使用脉冲相热成像（PPT），使用二维编织碳纤维环氧层压板以盲频校准缺陷深度。校准样品包含聚合物泡沫夹杂物形式的模拟缺陷。然后将校准后的深度与盲频之间的关系应用于由于低速冲击而几乎看不见的冲击破坏的样品。结果表明，与钻孔或具有较高热对比度的镶块相比，使用聚合物镶块模拟缺陷可以提供类似于在受冲击样品中观察到的热相移。尽管模拟损伤和冲击损伤之间存在差异（例如，不规则边界和分层的薄性），但从PPT图像计算得出的从冲击表面起的最小分层深度以及样品后表面的损伤程度仍在显示下一组层压复合材料样本是用嵌入式FBG传感器制造的，以测试使用脉冲相热成像和FBG传感器识别冲击破坏严重程度的组合检查方法的能力。最初，三组标本在中平面包含单个FBG传感器，以及来自先前研究的数据，用于优化FBG传感器产生的低速冲击损伤的距离，并优化FBG询问器的数据采集率。这些样品的结果表明，在冷却过程中，FBG传感器的温度测量值存在较大的偏差。另外，由于其电导率低，样品需要很长时间冷却，从而增加了检查时间。因此，对于最终样品，FBG传感器数据采集是在加热瞬态过程中进行的。最终的样品包含三个FBG传感器，分别埋入不同的深度，并用于量化不同严重程度的冲击破坏的起因和厚度变化过程。脉冲相位热成像技术用于冲击损伤的整体评估，这意味着可以量化绝对损伤的大小，也可以根据损伤和原始样品区域之间的相位对比来量化损伤的严重程度。结果表明，在损坏开始期间，内部FBG温度传感器的灵敏度要高于PPT。 PPT图像能够在损坏过程中捕获后期的图像。目视检查，显微图像和PPT结果用于比较FBG传感器检测到的不同深度处的损坏模式和严重程度。然后，基于组合检查方法的结果来制定损害评估模型。

著录项

  • 作者

    Pawar, Sachin Sampatrao.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Engineering Aerospace.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 141 p.
  • 总页数 141
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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