Havacılık sektöründe kullanılan kompozit malzemelerin yangına karşı davranışlarının incelenmesi = Investigation of the behavior of composite materials used in aviation industry against fire

Abstract

Bu çalışmada, hava araçlarının yapısallarında kullanılan kompozit malzemelerin, olası bir yangına karşı malzeme özelliklerindeki değişimi incelenmiştir. Havacılık malzemesi olan kompozitin, kontrolsüz yanma deneyi sonucundaki mekanik karakteristiği oluşturulmuştur. Üç aşamadan oluşan bu tez çalışması, sırasıyla; "kompozit numunelerin üretimi", "yangın deneyi" ve "mekanik davranışların incelenmesi" operasyonlarını içerir. Farklı kalınlıklardaki "kompozit numunelerin üretimi", prepreg UD E-glass fiber (elektrik geçirgenliğine karşı dirençli cam elyaf) malzemeden, hand lay-up ve otoklav curing imalat yöntemleriyle oluşturulan bir step lamine plakasının frezelenerek deney standart formlarına kesilmesiyle gerçekleştirilmiştir. Her bir numune, belirli zaman periyotlarıyla, laminer akışlı propan alevinden oluşturulan "yangın deneyi"nde yakılmıştır. Yanmış kompozit numunelerin çekme dayanımı deneyi ile "mekanik davranışların incelenmesi" sonucunda ise, 132 adet numune datası kayıt altına alınmıştır. Araştırmalardan elde edilen bulgularda, havacılık malzemesi numunelerinden, belirli oranlarda yanmış ve tahrip olmuş olanlarının, yanmamış referans olanlara göre mekanik davranışları karşılaştırılmıştır. Zamana bağlı yanma etkisinin, malzeme özelliklerindeki gerilmeye ve dayanıma olan etkileri incelenmiş ve bunların raporları tez çalışmasının sonucu olarak gösterilmiştir.

In this study, the changes in the material properties of composite materials used in aircraft structures against a possible fire were investigated. Mechanical properties of composites used in aircrafts have been formed at the end of the uncontrolled burning test. This thesis study, which is formed in three phases, covers the operations, respectively, "the production of composite samples", "fire test" and "investigation of mechanical behaviours". Composite samples producted in different wall thickness, which are made by UD E-glass fiber prepreg material, have been manufactured in the test standart forms after milling cut, following hand lay-up and autoclave curing processes of a laid laminate plate. Each sample has been burned in the fire test caused by propan laminer flow flame during specific time periods. 132 sample data have been recorded at the end of "investigation of mechanical behaviours" by means of tensile strength test of burned composite samples. Gained from the studies of aircraft materials samples, outputs of mechanical behaviours have been compared according to unburned reffered ones against the ones burned in certain rates and destructed. Time-dependet burning effects, which are the outputs related with the tension and durance characteristics of the material, have been studied and concerning reports have been put forth as the results of the case study. Usage area of composite materials, in aviation and defence industry, is getting increase by means of development day by day. Composite materials are used in the platforms of the aircrafts such as; planes, helicopters, unmanned aerial vehicles, armed unmanned aerial vehicles, drones and weapons. Also composite materials are used in the platforms of land vehicles such as; tanks, armored personel carriers, unmanned land vehicles, mobilized weapon systems and weapon structures, ammo structures. Also composite materials are used in naval vessels, such as; submarines, vessels, unmanned navel vessels. Besides them, their useage and development taken into the consideration are wide spread in military technologies such as; radar, armor, heat shields, low visible technologies. The density and strength rates of the composite mateials, in being so low rate, become across us in clear currency, in the adventagely usage of in high rate and also open development in the especially military armor technologies. Composite materials are being developed in the armor technologies, especially under the headline of bullet proof. E-glass (glass fiber materials resisting electricitiy conductivity), in the group of polimer matrix, are taken place in all over the cabinet of helicopters and commercial airplanes platforms in order to protect people from problems caused by thunderbolt and static electricity. Composite materials, in defence and aviation industry, have great importance than the other different materials with the characterisics of strength and lightness. They are used in the aviation platforms, especially all over the fuselage and alsa in the some structural constructions. Also, in the area of dissipating and producing heat (engine area etc.) of the aircraft platform, the heat isolator composite materials are placed to reduce the thermal trace of the aircraft in the air. Fire, which could be putout during the aviation operations or in the flight preparatory operations will affect the fusulage (inner or outer) and constructional integrity – soudness – of the aircraft. This effect is directly related with the fire resistance of the composite materials. For the reason of the production of composite materials manufactured by different components and different methods, each of them shows up different fire resistance and combustion strength. The wall thickness of the composite material is one of the resistance effects, and is be directly proportionate to the resistance against to the fire. In this study, how the resisting characteristics will show changeability are studied after a composites materials faced to fire. Composite samples producted in different wall thickness are tested in different periods to the laminer propan flames in 6,2L/h fluidity. The samples conducted against the flame are studied how the strength characteristics changed following tensile tests. This study is in the quality of a pilot study designed in order to major strength of combustion, researching the effects of uncontrolled combustion – fire how and how much will be, and also how this material will react to this effect. For this reason, this study can be used as a reference in aviation and defence industry. Besides, the tests, which will be performed with the changeable parametre variations in the future, can be put forward in the calculation and analyses of resistance of composite materials in fire used in different industries. Composite materials must be tested in absolutely controlled fire in order to simulate the destruction of the fire effects in the real enviromental conditions or else in the laboratory conditions. Heat conductivity shall be the same for the composite material as in the same heat conductivity in the heat resistant. For this reason, it is necessary to take in the considiration the composite materials parameters to be chosen as in wall thickness, and the outcomes of the heat resistance according to wall thickness. The fire test in this study, comparableness of the composite materials, which are used in the cabinet of aircraft and inner constructions, and in the inner panels, are shown according to each other after changing their wall thickness factors respectively. Composite material samples, which are in different wall thickness cut from the same panel (in the same structural materials), are burned with the laminer propan gas in the test, and then recorded separately in order to be sent to the tensile test. Also the strength of the composite materials recorded and reported as the results following the tensile test. There will be mellowing, deviation, delamination and ash formation at the matrix and fibers of the polymer composites after being subjected to the fire. Matrix mellowing, fiber and matrix delaminations and weakness of fibers decrase the tensile strength. The main aim of the fire test formation is to enable comparatively analyse the mechanical characteristic of same material after being cut in accordance with the tensile strength standarts and after being burnt at the neck sides of the formated composite samples. In the test of fire test process, controlled test has been done and laminer flow flame has been used. As we faced in numerous studies, definite and standart formation is not applied in the fire test formation. But in the name of comparableness the studies and their results, there are some definite methods. The hypothesis in this study is: "If a standart test formation is formed with the parameters of wall thickness, flame being exposed and period to the E – glass fiber composite materials used mainly within the aircraft fuselage, it will be predictable that how much the fire will give harm to the structural construction, after the analyse of the mantioned test results." By this way, a national contrabution will be provided to the calculation of aircraft strength calculations, the pariod of being in the air, the safety of pilot and logistics chains for materials at the national level. One of the main ideas in this study is to incrase test experience and to gain concrete data from the composite materials. As we understand from the analysis data and material behaviours at the end of tensile strength test, there is directly proportionate to the heat resistance and material wall thickness. Composite material begins to burn by itself for the reason of the matrix material being melted. As the result, variability of period points has been revealed from critical burning noticed from the graphics peak points. For this reason, the load of fire turns to the expansionary level from directly proportionated level of the wall thickness and heat resistance factor. This study is developed for the aim of and in the scope of methods in order to notice the combustion strength analysis of the materials to improve within the content of fire fighting. From the test results, graphics of glass fiber materials which are generally used within the cabinet of the aircraft have been recorded and the tensile strength results are reported. Results of the tests will be issued. As the result, its aimed that the results will have great contribution to the composite material industry, their needs, after sharing with the Turkish academic world and Turkish aviation and defence industry.