In this work, we describe a method for using fluorescent dyes in S-2 glass/epoxy composite samples to increase the contrast at the point of impact and the surrounding area for macroscale damage characterization. A sample measuring 6 cm x 5 cm was cut from three-parent composite materials (original size 20 cm in diameter) that was impacted with initial velocities of Vi = 166 m/s, Vi = 177 m/s and Vi = 186 m/s. High-resolution images of the cut samples were obtained using an 80-MP camera. After immersion of samples in either a pyrene (blue dye), fluorescein-FITC (green dye), or sulforhodamine dye (red dye) fluorophore solution (concentrations are &gt;1 mg/mL), the samples were transferred to an oven at 100 ○C for 10 minutes before five consecutive washes with deionized water and ethanol. Fluorescence images were obtained after each wash using a Cytation 5 Cell Imager. Optical and fluorescence images were manually evaluated for transverse and matrix cracks, which are special characteristics used to assess material failure. In conclusion, we observed that the green dye displayed the most contrast compared to the blue and red dyes, which allowed for better overall damage quantification. Furthermore, the blue dye allowed for better damage characterization at the point of impact. The red dye exhibited excellent contrast at the point of impact for characterization of tow-tow delamination. Our observations indicate that fluorescent dyes present valuable tools to enhance contrast in composite materials for damage evaluation.

Fluorescence-based contrast enhancement for macroscale damage characterization of S-2 glass/epoxy composite laminates

2019 Spring National Meeting

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