Mechanical properties and characterization of flame retardant thermoset composites after repair with UP and UV resin

Composite materials are materials formed by combining two or more components. Polymer matrix composites provide advantages such as light weight, high specific strength and modulus. The matrix mostly used in the industry is polyester (UP) resin. However, photocurable (UV) resins have also been used recently. Compared to traditional resins, they provide ease of application, short cycle time and easy equipment cleaning. Some additives can be used to add flame retardant properties to composite materials. Aluminum Trihydrate (ATH), Ammonium Polyphosphate (APP) and Zinc Borate (ZB) are some of these additives. Composites are products that can be repaired when damaged. Especially in assembly or structural joining processes, holes can be drilled into composite structures for fasteners. During maintenance and production, problems may occur due to missing fasteners, poor or incorrect assembly. In such cases, producing the part from scratch is a loss in terms of both time and cost. For this reason, there are many repair methods developed for composites. Repair with chopped fibers and patch repair are some of these methods. In the thesis study, glass fiber reinforced polyester composites were produced and flame retardant additives ATH, APP and ZB were added to the composites at the ratios of 10%, 15% and 20% according to the resin weight. Holes with a diameter of 5 mm were drilled at the center points of the composite samples. These holes were repaired using UV resin and UP resin. At the repair stage, the hole was first filled with resin containing chopped glass fiber, and then one layer of fiber was patched on the front and back of the perforated surface. Vacuum bagging method was used to consolidate the plies together. Mechanical properties, glass fiber ratio and combustion behavior of the composite were investigated before and after repair process. As a result of the study, according to the tensile tests, an increase in mechanical properties was observed with the addition of 10% ATH compared to the initial composite. In tensile tests, N10ATH group gave the highest result with 182 MPa among the undamaged and additive groups and N10UV group gave the highest result with 134.48 MPa among the repaired groups. In flexural tests, composites containing 15% APP reached the highest value in all groups. Among the undamaged groups, it provided an increase of 33.09 MPa compared to the initial composite. In the repaired groups, the highest value was obtained from the structures with 15% APP addition. According to the glass fiber content results, the ratio obtained after repair was again seen in the composite with 10% APP addition. In the horizontal combustion results, the flame did not progress in any of the groups containing APP and extinguished on its own. When the UP and UV repair results are compared, it is concluded that when UV cured resin is used instead of UP resin, the process can be advanced by saving time without compromising the mechanical and combustion behavior properties. It was concluded that there was some increase in mechanical properties with the addition of flame retardant additives. Both mechanical properties and combustion behavior properties can be improved with flame retardant additives used at a certain ratio. As a result of the study, it was concluded that when UV cured resin is used instead of UP resin, which is traditionally used in the sector in the repair stage, the process can be advanced by saving time without compromising the mechanical and combustion behavior properties. It was concluded that there was some increase in mechanical properties with the addition of flame retardant additives. Both mechanical properties and combustion behavior properties can be improved with flame retardant additives used at a certain ratio.