Carbon fiber composite has high specific stiffness and strength compared conventional metallic material. However, due to characteristics of stacking material, properties of their in-plane direction are excellent, but the thickness direction properties are weak. As a result, fatigue loads and low-speed impacts on the material may cause damage, such as separation between layers, through microcrack advancement inside the material. It is hard to identify and if we leave it can lead to complete failure of the structure. So failure monitoring technique is required for real-time evaluating structural integrity by applying a sensor system to the structure.
In this paper, proposed I-fiber stitching method which to reinforce the thickness direction properties of composite materials applied to single-lap joint specimen and evaluated its characteristics. At the same time, failure monitoring system was developed using AE and the electrical resistance method to detect real-time failure signals during the single-lap joint tensile test.