Hibrit fiber kompozit malzemelerin mekanik özelliklerinin deneysel olarak incelenmesi
Experimental investigation of mechanical properties of hybrid fiber composite materials
Yazar: FATİH EMİR DANYILDIZ
Danışman: DOÇ. DR. SEÇİL EKŞİ
Sakarya Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Makine Tasarım ve İmalat Bilim Dalı
Derece: Yüksek Lisans, 2023
Konu: Makine Mühendisliği = Mechanical Engineering

Özet:
Mekanik özelliklerin iyileştirilmesi ve maliyetlerin azaltılması için geliştirilen yeni 
imalat teknolojileri ve alternatif malzemelerin kullanımı en önemli araştırma 
konularındandır. Savunma sanayi, havacılık sektörü, otomotiv endüstrisi, uzay 
teknolojileri ve enerji gibi pek çok sektöre ait çalışmalarda kullanılan mevcut 
malzemelere alternatif malzeme olarak araştırılan malzemelerden biri de hibrit 
kompozit malzemelerdir. Hibrit kompozitler, günümüzde farklı elyaf türlerinin 
takviye elemanı olarak kullanılabilmesi ile ilgi çekici hale gelmiştir. Hibrit 
kompozitler farklı takviye malzemelerinin sahip oldukları özellikleri tek bir yapıda 
bulundurdukları için mekanik özellikleri üstünlük göstermektedir. Bu malzemelerin 
özellikleri ile ilgili sürekli araştırma yapılmaktadır. Bu malzemelerin performanslarını 
arttırmak için farklı elyaflar, farklı diziliş sıraları aynı kompozit yapıda kullanılarak 
hibrit kompozit yapılar elde edilecektir.
Bu çalışmada takviye malzemesi olarak aramid fiber, karbon fiber ve cam fiber 
kullanılmıştır. Karbon fiber olarak plain dokuma ve yoğunluğu 200 g/mm2
olan serisi 
kullanılmıştır. Aramid fiber olarak twill dokuma ve yoğunluğu 170 g/mm2
olan serisi 
kullanılmıştır. Cam fiber olarak twill dokuma ve yoğunluğu 280 g/mm2
olan serisi 
kullanılmıştır. Epoksi reçine ağırlıkça 100/40 oranında sertleştirici ile homojen bir 
karışım hazırlanmıştır. Karbon fiber, cam fiber ve aramid fiberler epoksi reçinesi ile 
birleştirilerek farklı kombinasyonlarda 6 adet hibrit plaka oluşturulmuştur. 
Hazırlanmış olan hibrit yapıdaki kompozit plakalar 6 katmanlıdır. Oluşturulan hibrit 
plakalar elle yatırma yöntemi ile üretilmiştir. Karbon fiber, aramid fiber ve cam 
fiberler ile oluşturulan farklı kombinasyonlardaki 6 hibrit plaka 1 gün boyunca oda 
sıcaklığında bekletilmiştir. Oluşturulan hibrit plakalar CNC dikey işleme 
merkezinde kesilerek numuneler elde edilmiştir. Bu çalışmada el yatırma yöntemi ile 
cam, karbon ve aramid fiberlerin farklı diziliş sıraları için mekanik özellikleri 
incelenmiştir. Mekanik özellikleri incelemek amacıyla çekme, üç nokta eğme ve darbe 
deneyleri gerçekleştirilmiştir. Çekme testinde gerilme-birim şekil değiştirme grafikleri 
oluşturulmuştur. Üç nokta eğme testinde kuvvet-deplasman grafikleri oluşturulmuştur. 
Darbe testinde ise farklı hibrit kompozit yapıların darbe dayanımları incelenmiştir.
Çekme deneyi sonuçları incelendiğinde 3K+3C numunesi en yüksek çekme 
dayanımına, 2K+2C+2A numunesi ise en düşük çekme dayanımına sahip olduğu 
görülmüştür. Elastiklik modülü en yüksek olan numune 3K+3C, en düşük olan 
numune ise 3A+3C numunesinde elde edilmiştir. Eğme deneyi sonuçları 
incelendiğinde en yüksek yük taşıma kapasitesine sahip olan numune 2C+2A+2K
kombinasyonuna, en düşük yük taşıma kapasitesine sahip olan numune ise 3A+3C 
kombinasyonuna aittir. Eğme deneyinde kombinasyonların diziliş sırasının yanında 
kombinasyonların ters çevrilmesi mekanik özellikleri etkilediği görülmüştür. 
Darbe deneyinden elde edilen verilerde ise darbe enerjisi en yüksek olan kombinasyon 
2K+2C+2A, en düşük darbe enerjisine sahip kombinasyon ise 3K+3C'dir. Elde edilen 
sonuçlara göre farklı fiber türlerinin diziliş sırasının hibrit kompozit malzemeler 
üzerinde etkisinin olduğu görülmüştür.

Abstract:
The use of new manufacturing technologies and alternative materials developed to 
improve mechanical properties and reduce costs are among the most important 
research topics. Hybrid composite materials are one of the materials researched as an 
alternative material to existing materials used in studies in many sectors such as the 
defense industry, aerospace industry, automotive industry, space technologies and 
energy. Hybrid composites have become interesting with the use of different fiber 
types as reinforcement elements today. Hybrid composites have superior mechanical 
properties because they contain the properties of different reinforcement materials in 
a single structure.
Hybrid composites formed by two or more different fibers in the same matrix form a 
new fiber-reinforced composite material group, unlike other composite types. Hybrid 
composites have better mechanical properties in all respects than composites 
consisting of only a single fiber in the matrix. In hybrid composites where very 
different matrix and fiber combinations are used, the most preferred hybrid is the type 
consisting of a polymer-based matrix that combines carbon fiber and glass fiber. 
Carbon fiber, with its stronger and higher rigidity, provides low density reinforcement, 
but is expensive. However, although glass fiber is cheap and easily available, it does 
not have the strength values provided by carbon fiber. The combination of glass fiber 
and carbon fiber provides stronger, tougher and higher impact resistance. This feature; 
can be obtained at a lower cost than all carbon fiber or all glass fiber reinforced plastics.
Hybrid composites are more advanced than other fiber-reinforced composites and have 
a wider range of potential applications. Two different fibers, which have a significant 
impact on the overall properties of the composite, can be combined in many different 
ways. For example, both types of fibers can be mixed together and placed all in the 
same direction, or it can be prepared by sequentially placing layers, each containing a 
single type of fiber, one after the other. The properties of almost all hybrid composites 
are direction dependent. When hybrid composites are subjected to a tensile type of 
stress, damage usually does not occur suddenly. First, the reinforcing element with a 
high strength value meets the load, and then this load is transferred to the other 
reinforcing elements. Matrix phase fracture also occurs after all the reinforcement 
phases have undergone fracture. Ultimately, damage to the composite occurs 
simultaneously with damage to the matrix. There is constant research on the properties 
of these materials. In order to increase the performance of these materials, hybrid 
composite structures will be obtained by using different fibers in the same composite 
structure.

In this study, aramid fiber, carbon fiber and glass fiber were used as reinforcement 
materials. Among the properties of carbon fibers, we can count high impact resistance, 
abrasion resistance and fatigue resistance. Carbon fibers are resistant to high 
temperatures. The disadvantage is that it causes impact resistance problems due to the 
limited elongation properties of its fibers. Aramid fiber is lighter and more rigid than 
glass fiber. Aramid fibers have low compressive strength. Therefore, it finds usage 
area by creating hybrid composite with carbon fiber. Due to their low compressive 
strength, aramid reinforced epoxy matrix composites also have poor moisture 
retention. The basis of glass fiber is silicon dioxide (SiO2). However, it can also 
contain oxides of elements such as aluminum, calcium, sodium boron and iron in a 
certain amount. Glass fibers have high resistance to chemicals and poor moisture 
absorption properties. Glass fiber is an inexpensive reinforcing material and is 
commonly used in plastic-based composites.
Plain weave and the series with a density of 200 g/mm2 were used as carbon fiber. 
Twill weaving and the series with a density of 170 g/mm2
are used as aramid fiber. 
Twill weaving and the series with a density of 280 g/mm2 were used as glass fiber. A 
homogeneous mixture was prepared with epoxy resin and hardener at a weight ratio of 
100/40. Carbon fiber, glass fiber and aramid fibers were combined with epoxy resin to 
form 6 hybrid plates in different combinations. The created hybrid plates are 400×400 
mm in size. The prepared hybrid composite plates have 6 layers. The created hybrid 
plates were produced by hand lay-up method. 6 hybrid plates in different combinations 
formed with carbon fiber, aramid fiber and glass fibers were kept at room temperature 
for 1 day. The created hybrid plates were cut in CNC vertical machining center and 
samples were obtained. In this study, the mechanical properties of glass, carbon and 
aramid fibers for different arrays were investigated by hand lay-up method.
The purpose of the tensile test; To determine the elastic and plastic behavior of 
materials under static load. For this, a circular or rectangular test piece with dimensions 
in accordance with the standards; By connecting to the pulling device, axial and 
variable forces are applied. The bending test is performed to determine the design 
information about the strength of the material and to determine the mechanical 
properties of the material against bending. Izod impact test determines the energy 
consumed to break the sample with the impact of a hammer at the tip of a pendulum 
at a certain height from a vertical and cantilevered gripping jaw and the effect of 
multiaxial stresses occurring at the bottom of the notch.
Tensile, three-point bending and impact tests were carried out to examine the 
mechanical properties. Stress-strain graphs were created in the tensile test. Forcedisplacement graphs were created in the three-point bending test. In the impact test, 
the impact strength of different hybrid composite structures was investigated.
The tensile test was carried out on a Dartec brand test device with a load capacity of 
30 tons. Tensile test was performed according to ASTM D3039 standard. In the tensile 
test, samples of 250x25 mm dimensions were prepared from each combination. In the 
tensile test, the samples were tested with a tensile speed of 2 mm/min. Three point 
bending tests were carried out on a Zwick/Roell test device with a load capacity of 5 
tons. Test samples of 125x13 mm dimensions were prepared from each combination 
in accordance with ASTM D790 standard. In the three-point bending test, the samples 
were tested with a bending speed of 2 mm/min. Izod impact test was performed 
according to ASTM 4812 standard. Samples of 65x13 mm dimensions were prepared 
from each combination. Alerge brand izod impact tester was used. The experiment was 
carried out with a 5.5 Joule hammer.
When the tensile test results were examined, it was seen that the 3K+3C sample had 
the greatest tensile strength with a tensile strength of 351.47 MPa. The 3A+3C sample 
is in second place with a tensile strength of 301.03 MPa. The 2K+2C+2A sample has 
the lowest tensile strength of 225.47 MPa. The sample with the highest modulus of 
elasticity was 3K+3C, and the sample with the lowest was obtained from the 3A+3C 
sample. The combination of 3K+3C with a high modulus of elasticity is more rigid 
than other combinations.
In the bending test, the highest load carrying capacity was obtained with 259.41 N in 
combination with 2C+2A+2K. The lowest load carrying capacity was observed in the 
3A+3C sample with 87.74 N. In the bending test, it was seen that the order of the 
combinations as well as the inversion of the combinations affected the mechanical 
properties.
In the data obtained from the impact test, the combination with the highest impact 
energy is 2K+2C+2A, and the combination with the lowest impact energy is 3K+3C. 
Impact resistance is high in groups with aramid fiber in impact tests. The reason for 
this is thought to be the high tensile strength and percent elongation values of aramid 
fiber.
According to the results obtained, it was seen that the order of the different fiber types 
had an effect on the hybrid composite materials.