Investigation of circular damage repairing by using adhesive in laminate composite materials experimentaly

In recent years, composite materials have been used extensively in all areas of the industry parallel to the development of technology in land, air, sea and space vehicles. Since such materials are difficult to recycle and reusing, there are ecological problems in the environment. For this reason, repairs of such materials are carried out in order to reuse damaged parts rather than dismantling and installing new materials. In addition, these materials are new technological materials and their costs are high. That is why, their repairs are preferred. Thus, repairs of such nonmetallic materials are becoming increasingly important. Especially, repairs of the outer shells and wing parts in the air planes that damaged by accidental bullets and striking objects (such as birds etc.) which are particularly important in terms of strength are carried out by this type of patch bonding repair technique. In this study, 10 mm circular damage was created after 8 layers of composite sheets with woven glass and carbon fibers reinforcement were produced. Borders of these damages (bonding area) in parent materials were subjected to mechanical operations and then, these damages were repaired by patch bonding technique with different adhesives and different patches in suitable laboratory (environmental) conditions. In the experiments carried out, the factors affecting the quality of the repair (ultimate damage load) were investigated. These factors include; Diameter/width of composite plate ratio, adhesive thickness, adhesive types, the change of fiber reinforcement angle (0°,15°,30°,45°), patch thickness and patch geometry. The obtained results were transferred to the graphs and compared and discussed with the existing study results presented in the literature.