Comparison of off-axis angle on the low velocity impact behaviors for carbon-fiber-reinforced polymer laminates

Three types of composite specimens with different off-axis angles after indentation were subjected to progressive tensile loading, and the results showed that although the tensile strength is reduced with an increase in off-axis fiber orientation angle, such off-axial structure can enhance the impact-resistance capacity. An acoustic emission (AE) signals analysis showed that data can be divided into categories that correlate with three damage modes. The AE peak frequency characteristics of each damage mode were also identified for both specimens with and without indentation, and the results also showed that indentation can change the order of appearance of different damage modes during loading. Additional characterization was provided by using Micro-computed tomography (Micro-CT) during a progressive tensile loading process, and the CT images provided visualization of damage location and evolution in the composites, with the data exhibiting good correlations with the AE data for defect prediction. The use of AE and Micro-CT technology was shown to effectively characterize composite damage evolution, and such data can potentially serve as a reference for the structural health monitoring (SHM) of such composites when used in structures.