Delikli kompozit yapılarda boyutsal özelliklerin dayanım değerlerine etkisinin deneysel ve analitik olarak incelenmesi

In this thesis, we investigate the effect of size on the strength of open hole composite laminates using experimental and analytical approaches. The size effect consists of the effect of thickness and hole size while keeping width to diameter ratio constant. In the experimental part of this work, tensile tests are conducted on CFRP open hole specimens. In-situ images of the top and side surfaces of the test specimens are captured throughout the experiments and load displacement curves are acquired from the testing machine. The top surface images are captured using high resolution camera and analyzed with digital image correlation (DIC) technique. The side surface images are captured using high speed camera setup and these images and post-mortem microscope images are used to determine failure mechanisms. Finally, in agreement with the literature, size dependence is observed on a plot of failure stress vs. hole size. On the analytical part of this work, an analytical methodology is developed based on Tan's approach. The stress field is calculated using Lekhnitskii's Formulation and Classical Lamination Theory(CLT). The analytical strength prediction of the open hole composite laminate is done according to First-Ply-Fiber-Failure(FPFF) methodology. The analytical model performs well compared to other models in the literature in modeling the size dependence of the failure stress on the hole size.