No abstract

The mechanical properties of sandwich composites are more depended on the core material structure. Damage of the commercial honeycomb core materials are generally occurred as delamination the unit-cells of core material under mechanical or impact loads. In addition, the common feature of commercial core materials is their high-cost. Economic approach of the current researches are led the studies based on the principle of converting ordinary materials into advanced materials. Nowadays, the development of low-cost/high-performance products that serve to reduce environmental impact is an important requirement. In present study, a novel core material is developed for sandwich composites by using a special stitching design. The developed core structure is defined as ‘rhombus core’ which offers a lower cost/higher performance compared to commercial core materials. The compressive behavior of rhombus and commercial core structures are compared. Rhombus cores showed the highest compressive strength and retained their structural integrity after compressive load without any delamination/crushing at stitching regions.

Using textile structural composites improves day by day in various industries due to their high specific strength and modulus, good fatigue and corrosion resistance. The most important reasons for the increased use of textile structural composites are the increased expectations for product performance and demand for lightweight materials in global markets. Rapid economic growth, urbanization, rising in population and welfare level lead to an increased amount of waste production. In Turkey, the annual average of solid waste is 25 million tons and 20% of this waste consists of packaging wastes. In this study, a new sandwich material was developed for construction applications with low cost and high performance by using box wastes as core and E-Glass woven fabric as sheet materials. The mechanical properties of sandwich composites were investigated by 3-point flexural test and their impact behavior was compared after low-velocity impact tests in different energy levels. The core material had a negligible flexural strength. The flexural load of sandwich composites was dramatically higher than those of face material. Low-velocity impact results showed that absorbed energy and damaged area increased with increasing impact energy. It could be concluded that the developed sandwich composites absorb more energy with small damaged areas and therefore can be considered as damage resistant materials for constructional applications such as door and siding. ÖzTekstil yapısal kompozitlerin kullanımı, yüksek özgül dayanım ve modülü, iyi yorulma ve korozyon direncinden dolayı, çeşitli endüstrilerde günden güne artmaktadır. Tekstil yapısal kompozitlerinin kullanımının artmasının en önemli nedenleri, küresel pazarda ürün performansı ve hafif malzemelere olan talebin artmasıdır. Hızlı ekonomik büyüme, kentleşme, nüfus ve refah düzeyindeki artış, atık miktarının da artmasına yol açmaktadır. Türkiye'de yıllık ortalama katı atık miktarı 25 milyon tondur ve bu atığın %20'sini ambalaj atıkları oluşturmaktadır. Bu çalışmada inşaat uygulamaları için, çekirdek olarak atık karton kutu ve dış yüzey malzeme olarak E-Cam dokuma kumaşın kullanıldığı düşük maliyetli ve yüksek performanslı yeni bir sandviç malzeme geliştirilmiştir. Sandviç kompozitlerin mekanik özellikleri 3-nokta eğilme testi ile incelenmiş ve farklı enerji seviyelerinde düşük hızlı darbe testlerinden sonra darbe davranışları karşılaştırılmıştır.Çekirdek malzeme ihmal edilebilir bir eğilme dayanımı göstermiştir. Sandviç kompozitlerin eğilme yükü, dış yüzey malzemelerden çok daha yüksektir. Düşük-hız darbe sonuçları, absorbe edilen enerjinin ve hasarlı alanın artan darbe enerjisiyle birlikte arttığını göstermiştir. Geliştirilen sandviç kompozitlerin daha az hasarlı bölge ile daha fazla enerji absorpladığı belirlenmiş ve bu nedenle kapı ve dış cephe kaplama gibi inşaat uygulamaları için hasara dayanıklı malzemeler olarak kabul edilebileceği sonucuna varılmıştır.Anahtar Kelimeler: Sandviç kompozitler, Atık-ambalaj/E-Cam/epoksi sandviç kompozitler, Eğilme dayanımı, Darbe direnci. San...

This experimental study investigates the flexural response of sandwich composites integrated with 3D multi-layer stitched core. Polypropylene 3D multi-layer woven fabric impregnated with an epoxy resin was selected as the core, while E-glass fiber reinforced epoxy was used for the sandwich composite face sheets. The sandwich composite exhibited a ductile behavior when loaded in three-point bending as the core layers increased. This is due to the drop in core shear strength with the increased number of core layers. The core layers that were not directly connected with the face sheets deformed most under shear, resulting in a more flexible plate behavior. The number of core layers, size of core unit-cell and stitching density were the critical design parameters determining the flexural strength and stiffness of the sandwich panel. The flexural modulus of sandwich composites with higher stitching density core stiffer than those of lower stitching density.