<p>Damages developed in composite structures by low impact forces is not visible on the top surface of the composite most of the time. But the impact damage propagates within the layers inside the composite and sometimes reaches the bottom surface in the form of delamination or internal cracks. Such incidences pose a risk of structural failure so should be addressed and analyzed as early as possible for the safety of the entire system. This work proposes a nondestructive health monitoring method of materials using ultrasonic waves. &nbsp;The scanning acoustic microscope (SAM) employed for such inspections uses a transducer to emit high frequency wide-band ultrasonic waves which interact with the top surface as well as penetrate through the material to reveal the internal picture. &nbsp;Individual data points in various layers throughout the thickness is recorded and processed which are later used to create images of individual internal layers at varying depths to demonstrate the cracks and delamination developed due to impact. Such images can be evaluated to define the structural health of the material. These internal layer images can be stacked together to create a combined image of the damaged area and a quantitative acoustic contrast tomograph. Conversion of the tomographic image to a finite element model will allow a detailed analysis, inspection and quantification of the internal damage condition of the material and thus the entire structure. Preliminary analysis of few low impacted composite plates reveals the effectiveness of this method. &nbsp;The results demonstrate that such tomographic images can detect and quantify internal damages of a composite very effectively. Since composites vary in layers, symmetry, and orientation of the fibers, a quantitative analysis of the material using these tomographs can characterize damage and crack propagation, path of the impact energy throughout the layers, composite’s ability to withstand impact and damage between various types of composite materials. &nbsp;</p>

Investigation and Quantification of Internal Damage Propagation in Impacted Composite Plates Using Acoustic Contrast Tomograph

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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