Malzemeleri yüksek mekanik özelliklerde, daha düşük maliyetlerle imal etmek günümüz endüstrisindeki en büyük araştırma ve geliştirme konularından biridir. Kompozit malzemeler, savunma, havacılık, otomotiv sanayi, uzay teknolojileri ve enerji gibi sektörlere ait çeşitli imalatlarda kullanılan mevcut malzemelerin yerine kullanılmak üzere araştırılan ve geliştirilen malzemelerden biridir. Kompozit malzemeler, değişik türdeki elyaf malzemelerin takviye elemanı olarak kullanılması ile avantajlı alternatif malzeme haline gelmiştir. Kompozit malzemeler, değişik takviye elemanlarının sahip oldukları özellikleri tek başına bulundurdukları için mekanik özellikleri ile avantajlı hale gelmektedir. Bu malzemelerin özellikleri ile ilgili sürekli araştırma yapılmaktadır. Yapılan araştırmalar ilerleyen zamanlarda kompozit malzemelerin endüstride daha sık kullanılacağını öngörmektedir. Bu malzemelerin mekanik özelliklerini daha da iyileştirmek için farklı elyaflar, farklı diziliş sıraları aynı kompozit yapıda kullanılarak kompozit malzemeler elde edilmektedir. Alüminyum alaşımları mekanik özellikleri, hafif olması ve ekonomik olması gibi sebepleriyle günümüz endüstrisinde geniş bir kullanım alanı sunmaktadır. Savunma sanayi, havacılık sektörü, otomotiv endüstrisi, kazan imalatları gibi birçok alanda sıkça tercih edilmektedir. Bu çalışmada farklı kalınlıklardaki iki alüminyum plaka arasına farklı elyaf türlerinden imal edilen kompozit malzemeler yapıştırılarak sandviç levhalar imal edilmiştir. Üretilen sandviç kompozit levhaların v-bükme işlemi sonrası geri yaylanma davranışları incelenmiştir. Bu çalışmada üretilen sandviç kompozit levhada kullanılan alüminyum alaşımı Al6061 serisi olup, ısıl işlem türü T6'dır. Bu çalışmada kullanılan alüminyum alaşımın 1mm ve 1,5mm kalınlığındadır. Deneyler 70x70 mm ölçülerindeki numunelerle yapılmıştır. Kullanılan alüminyum plaka kalınlığı ile aynı kalınlıkta ve aynı ölçülerde karbon elyaf, karbon-cam elyaf, cam elyaf ve aramid elyaf takviye malzemeli kompozit malzemeler üretilmiştir. Karbon elyaf olarak plain dokuma ve yoğunluğu 200 g/mm2 olan serisi kullanılmıştır. Karbon-cam elyaf olarak twill dokuma ve yoğunluğu 220 g/mm2 olan serisi kullanılmıştır Aramid elyaf olarak twill dokuma ve yoğunluğu 170 g/mm2 olan serisi kullanılmıştır. Cam elyaf olarak twill dokuma ve yoğunluğu 280 g/mm2 olan serisi kullanılmıştır. Kullanılan kumaş ağırlığının %60'ı kadar reçine ve 1⁄4 oranında sertleştirici kullanılarak homojen bir karışım hazırlanmıştır. İmal edilen sandviç levhalar farklı ölçülerdeki kalıp genişliklerinde, farklı kalıp açılarıyla CNC abkant preste V bükme deneyine tabii tutulmuştur. Bu deneylerden sonra geri ve ileri yaylanma miktarları ölçülmüştür. Bu sonuçlar incelendiğinde alüminyum-karbon elyaf ve alüminyum- karbon-cam elyaf malzemelerde geri yaylanma olduğu görülmüştür. Alüminyum-cam elyaf ve alüminyum-aramid elyaf malzemelerde ise ileri yaylanma olduğu görülmüştür. Alüminyum alaşımlı numunenin deneylerinde, malzeme kalınlığına uygun ölçüdeki v- bükme kalıbı kullanıldığında geri yaylanma, daha büyük ölçüdeki v-bükme kalıplarında ise ileri yaylanma tespit edilmiştir. Malzeme kalınlığına uygun ölçüdeki v-bükme alt kalıbı seçildiğinde istenilen sonuca daha yakın sonuçlar tespit edilmiştir.
Manufacturing materials with high mechanical properties and at lower costs is one of the biggest research and development issues in today's industry. Aluminum alloys offer a wide range of uses in today's industry due to their mechanical properties, light weight and economic nature. It is frequently preferred in many areas such as the defense industry, aviation industry, automotive industry and boiler manufacturing. Composite materials are one of the materials researched and developed as alternative materials to existing materials used in many sectors such as the defense industry, aviation industry, automotive industry, space technologies and energy. Composite material; It is defined as materials created by combining two or more materials of the same or different types at a macro level in order to collect their best properties in a new and single material. Composite materials become advantageous alternative materials by using different types of fiber materials as reinforcement elements. has arrived. Composite materials have superior mechanical properties because they contain the properties of different reinforcement materials in a single structure. In parallel with the development of technology, studies on composite materials created by combining different materials in order to obtain superior mechanical and physical properties according to their application areas have accelerated, as traditional materials alone cannot meet the needs. Research predicts that composite materials will be used more frequently in industry in the future. In order to further improve the mechanical properties of these materials, composite materials are obtained by using different fibers and different sequences in the same composite structure. Thanks to composite materials created by combining different types of materials on a macroscopic scale, properties such as lightness, high strength, fatigue life, rigidity, thermal conductivity, wear resistance and corrosion resistance can be improved. Sandwich composite structures are composite structures designed by using a light and low-strength core layer in the middle, surrounded by two surfaces called hard and high-strength shells, in order to benefit from the different properties of their components. Aluminum, titanium, steel, wood or concrete are generally used in the surface layers of sandwich composite structures. Cork, plastic, aluminum or fiber derivatives in honeycomb form are used in the core layer of sandwich composite sheets. Material properties of fiber materials such as corrosion resistance, lightness, high fatigue resistance and high strength have reduced the demand for metals. In addition to these superior properties of fibers, their low shaping ability is a disadvantage. To overcome this disadvantage, fibre-metal hybrid composites have been developed. In this study, fiber metal sandwich panels were manufactured by gluing composite materials made of different fiber types between two aluminum plates of different thicknesses. Fiber metal laminated composites are hybrid structures composed of different metal sheets (usually aluminum) and fiber reinforced polymer matrix composites such as carbon, glass or aramid. Today, it is widely used in the automobile,aircraft and aerospace industries. Compared to metals, sandwich composite sheets are preferred in many areas such as the aircraft industry, space technology, maritime industry and automotive industry, as they are lighter and have higher fatigue strength. As the usage areas of sandwich composite sheets increase, the need to shape sandwich composite sheets according to where they are used has emerged. Therefore, the forming ability of sandwich composite sheets was investigated. In the experimental study, it was investigated how the springback problem, which is one of the biggest problems encountered in the shaping of sheet metal materials, would affect sandwich composite sheets, which are preferred due to their high performance and resistance to environmental effects. Bending is a frequently used manufacturing process in shaping materials in modern industry. Bending; It can be defined as giving the desired shape to the part with the help of a mold, around a certain axis, without removing material from the material. The force applied in the bending process causes deformation on the material. If the force applied to the material during the bending process exceeds the yield value of the material, plastic deformation (permanent deformation) occurs, and if it does not exceed it, elastic deformation (non-permanent deformation) occurs. In the process of shaping the materials, the elastic limits of the materials are exceeded, but the greatest tensile stresses cannot be exceeded. Therefore, the material still retains some of its original flexibility. In the bending process, when the force applied to the material is removed, compressive stresses occur in the inner deformation zone of the material and tensile stresses occur in the outer deformation zone. When the force applied to the material is removed, the material tries to return to its initial state due to these stresses, and this causes the bent material to stretch and open. This phenomenon occurring in the material is called springback. Springback, which generally occurs after bending in sheet metal materials, removes the material from the final form and causes the desired dimensions to change. It has been determined that the stress and shape changes occurring in the bent material cross-section generally depend on the type of material, material thickness, bending angle, tip radius of the punch, bending force, ironing time, bending speed and the gap between the female mold and the punch. In this study, the springback behavior of the sandwich composite plates after the v- bending process was investigated. The aluminum alloy used is Al6061 series and the heat treatment type is T6. Thickness of aluminum sheets are 1 mm and 1.5 mm. The experiments were carried out with samples measuring 70x70 mm. Composite materials with carbon fiber, carbon-glass fiber, glass fiber and aramid fiber reinforcement materials were produced with the same thickness and dimensions as the aluminum plate thickness used. Plain weave series with a density of 200 g/mm2 were used as carbon fiber. Twill weave with a density of 220 g/mm2 was used as carbon-glass fiber. Twill weave with a density of 170 g/mm2 was used as aramid fiber. Twill woven series with a density of 280 g/mm2 was used as glass fiber. A homogeneous mixture was prepared by using 60% resin and 1⁄4 hardener by weight of the fabric used. The manufactured sandwich sheets were subjected to V bending tests on a CNC press brake with different mold widths and different die angles. After these experiments, the springback and spring-go amounts were measured. When these results were examined, it was seen that there was springback in aluminum- carbon fiber and aluminum-carbon-glass fiber materials. It has been observed that there is spring-go in aluminum-glass fiber and aluminum-aramid fiber materials. In the experiments of the aluminum alloy sample, springback was detected when a v-bending die of a size appropriate to the material thickness was used, and spring-go was detected in larger v-bending dies. When the v-bending sub-die suitable for the material thickness was selected, results closer to the desired result were determined.
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