Statik Yükleme Altında Oksetik İç Yapılı Sandviç Kompozitlerin İncelenmesi

Öz

Sandviç kompozitler, farklı malzeme kombinasyonları ile birleştirilerek özel uygulamalar için oluşturulabilen optimum malzeme tasarımlarıdır. Çok sayıda alternatif sandviç kompozit yapı biçimi ile farklı yüzey ve çekirdek malzemeler birleştirilebilir. Bu çalışmada; özellikle otomotiv tampon uygulamalarına yönelik olarak geliştirilen sandviç kompozit malzeme, naylon Poli-amid 12 (PA12) polimer malzemesinden oluşan çekirdek ile cam fiber takviyeli Polipropilen (GFRPP) alt – üst yüzeylerin bir araya getirilmesi ile elde edilmiştir. Malzemelerin önemli bir özelliği olan Poisson oranı; bir malzemenin kuvvet uygulandığı yöndeki şekil değiştirme miktarı ile aksi yöndeki şekil değiştirme miktarı arasındaki bağıntıyı verir. Poisson oranı birçok malzemede pozitif iken bazı malzemelerde ise negatiftir. Poisson oranı negatif olan bu malzemelere "oksetik malzeme" denir. Üretilen sandviç kompozitte negatif Poisson oranına sahip olan oksetik özellikteki çekirdek, üç boyutlu yazıcılardan birisi olan Fused Deposition Modelling (FDM) ile üretilmiştir. Girintili bal peteği geometrisi sayesinde üstün esneme özellikleri beklenmektedir. Bu amaçla; iki farklı kalınlıkta üretilen çekirdek geometrisine sahip olan sandviç kompozit malzemeler üç nokta eğme testlerine tabi tutulmuştur. Bu çalışma kapsamında mukavemet ve darbe absorbsiyonu açısından sandviç yapılarda kullanılan oksetik yapıların arasındaki mesafenin yapının kalınlığından daha önemli bir parametre olduğu ortaya konulmuştur.

Anahtar Kelimeler

• sandviç kompozit
• 3 boyutlu eklemeli imalat
• mekanik özellikler
• oksetik malzeme

Investigation of Sandwich Composites with Auxetic Core under Static Loading

Öz

Sandwich composites are optimum material designs that can be created for special applications by combining with different material combinations. Different surface and core materials can be combined with a number of alternative sandwich composite structures. In this study, the sandwich composite material, developed especially for automotive bumper applications, is obtained by combining the core consisting of nylon Polyamide 12 (PA12) polymer material and glass fiber reinforced Polypropylene (GFRPP) lower - upper surfaces. Poisson's ratio, which is an important property of materials; It gives the relationship between the amount of strain of a material in the direction in which the force is applied and the amount of strain in the opposite direction. Poisson's ratio is positive in many materials and negative in some materials. These materials with a negative Poisson ratio are called "oxetic materials". The core with negative Poisson ratio in the produced sandwich composite was produced with Fused Deposition Modeling (FDM), one of the three-dimensional printers. Superior flexing properties are expected thanks to the re-entrant honeycomb geometry. For this purpose, sandwich composite materials with core geometry produced in two different thicknesses were subjected to three-point bending tests. Within the scope of this study, it has been revealed that the distance between the oxetic structures used in sandwich structures is a more important parameter than the thickness of the structure in terms of strength and impact absorption.

Anahtar Kelimeler

• Sandwich composites
• 3D additive manufacturing
• mechanical properties
• oxetic material

Kaynakça

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