Evaluation of Surface Delamination in Drilled Fiber-Reinforced Polymer Composites Using Digital Image Processing

Drilling holes in fiber-reinforced polymer (FRP) laminates is complex because it can cause surface defects, such as micro damage, fiber pull-outs, and delamination. Incorrect measurement of these flaws around the holes can lead to significant stress concentrations, resulting in an unexpected failure of the machine components and causing financial or even fatal losses. This paper aims to demonstrate a novel and simple distance transforms technique in MATLAB with digital image processing to measure the delamination factor to access the drilling-induced damages on the surface of FRP plates. The image scanner was used to obtain microscopic images of the composite test specimens drilled surfaces. The input image was filtered to remove noise and enhanced by contrast stretching, contrast adjustment, and histogram equalization before being converted into a binary image. When the proposed method results were compared with the visual inspection technique, it was confirmed that the distance transforms approach with image processing can accurately measure the delamination factor in an efficient and simple manner. This is due to the fact that only the delaminated associated area is precisely considered when calculating the delamination factor in the image processing technique. © The Institution of Engineers (India) 2023.