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Karbon elyaf dokuma (5-HS) takviyelı termoplastık (PPS) kompozitte serim açısının balistik davranışa etkisi

The effect of layup angle on ballistic behavior in carbon fiber (5-HS) reinforced thermoplastic (PPS) composites

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  1. Tez No: 964651
  2. Yazar: YAVUZ GENEL
  3. Danışmanlar: DOÇ. DR. YAŞAR KAHRAMAN, DR. ÖĞR. ÜYESİ MUHAMMET MUAZ YALÇIN
  4. Tez Türü: Yüksek Lisans
  5. Konular: Makine Mühendisliği, Mechanical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2025
  8. Dil: Türkçe
  9. Üniversite: Sakarya Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Makine Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Makine Konstriksüyon ve İmalat Bilim Dalı
  13. Sayfa Sayısı: 81

Özet

Termoplastik matrisli dokuma kompozitler, günümüzde özellikle havacılık, savunma sanayi ve otomotiv sektörlerinde artan talep görmekte olup; yüksek darbe dayanımları, kimyasal ve termal kararlılıkları ile ön plana çıkmaktadır. Bu malzemeler, tekrar şekillendirilebilir olmaları ve geri dönüştürülebilir özellikleri sayesinde sürdürülebilir üretim hedefleri doğrultusunda da cazip bir çözüm sunmaktadır. Dokuma kompozitlerde, iki boyutlu dokuma desenleri arasında saten dokuma öne çıkmakta; liflerin daha az bükülmesi (düşük crimp) sayesinde yüklerin daha homojen taşınmasına imkan vermekte ve böylece daha üstün mekanik performans sergilemektedir. Ayrıca saten dokuma yapısının karmaşık geometriye sahip parçalarda deformasyona uğramadan uygulanabilmesi, üretim süreçlerini de kolaylaştırmaktadır. Bu çalışmada, beş iplikli saten (5-HS) karbon elyaf dokuma ile takviye edilen ve polifenilen sülfid (PPS) matrisli olarak üretilen termoplastik kompozit laminatların farklı serim açılarına bağlı balistik davranışları sayısal yöntemlerle detaylı biçimde incelenmiştir. Çalışmada kullanılan modeller, LS-DYNA sonlu elemanlar yazılımında oluşturulmuş; literatürde deneysel olarak doğrulanmış MAT58 kompozit malzeme model parametreleri ile Hashin hasar kriterleri temel alınarak modellenmiştir. Bunun yanı sıra, temas (contact) tanımlamaları ve kontrol parametreleri titizlikle yapılandırılarak daha gerçekçi sonuçlar elde edilmesi sağlanmıştır. Analizlerde [0]8, [0/90]4, [0/45]4, [±45]4 ve [0/45/-45/90]2 serim dizilimlerine sahip kompozit paneller tasarlanmış; her biri için 30 mm çapında çelik küre fragmanın 60 m/s ve 101,7 m/s hızlarında çarpma senaryoları modellenerek fragmanın paneli delip geçtikten sonraki çıkış hızı ve kompozit panelde oluşan hasar detaylı şekilde değerlendirilmiştir. Elde edilen bulgular, yüksek hız senaryosunda (Vi = 101,7 m/s) serim açısının fragman çıkış hızına etkisinin görece düşük olduğunu, buna karşın düşük hız durumunda serim açısının balistik performans üzerindeki etkisinin daha belirgin hale geldiğini ortaya koymuştur. Özellikle 45° serim açısının, enerjiyi daha etkin sönümleyerek fragman çıkış hızını azaltması ve panelde oluşan hasarı minimize etmesi açısından olumlu sonuçlar verdiği gözlemlenmiştir. Bu doğrultuda, mevcut numuneler içinde [45/0/45/0]2S dizilimli laminatların balistik direnç açısından daha avantajlı olduğu değerlendirilmiştir. Ayrıca laminat kalınlığının artırılmasının, düşük hızlardaki darbe senaryolarında panelin delinmesini engelleyerek hasar oluşumunu baskıladığı ve dolayısıyla balistik dayanımı anlamlı şekilde iyileştirdiği sonucuna ulaşılmıştır.

Özet (Çeviri)

As is well known, thermoplastic matrix woven composites are attracting significant attention due to their high impact resistance and dimensional stability. Furthermore, when evaluated in terms of fatigue behavior, carbon-reinforced composite materials exhibit superior properties compared to metal materials. Furthermore, among two dimensional weave patterns, satin weave is generally preferred due to its higher mechanical properties and ease of application to complex parts. The wider interweaving of the fibers allows for more uniform placement in complex-shaped molds. Furthermore, fewer bends and transition points reduce the risk of defects between layers, thus significantly reducing the likelihood of delamination. These advantages improve the impact and fatigue resistance of composite parts using this weave, particularly in the presence of impact and fatigue. Laminated composites consist of a series of unidirectional layers bonded together so that the fiber directions form different angles with the material axis. By controlling the number of layers and the fiber angle, the mechanical properties of the composite can be tailored to the specific task. Layered composites are categorized into two categories: symmetrical and asymmetrical. Different properties can be achieved depending on the material type selected. However, optimal performance and long service life can be achieved by using adhesive layers to ensure a perfect and durable bond between the layers. Due to their impact behavior, layered composites, while not causing significant damage under low velocity impacts, can cause serious delamination or matrix cracking in the internal structure. It is particularly beneficial to carefully examine critical components in the aerospace and defense industries. On the other hand, impacts from events such as bullets, shrapnel, or flying particles are more severe and are categorized as medium- or high-velocity impacts. Depending on the impact velocity, impact energy, and part tip geometry, composite materials can experience serious structural failures such as fiber breakage, delamination, localized matrix damage, and fragmentation. Of course, the impact energy and the geometry of the impacting part provide important information about the definition and effect of the damage mechanism. In this study, the ballistic behavior of samples consisting of polyphenylene sulfide matrix (CF/PPS) thermoplastic composite laminates reinforced with a five-strand satin carbon fiber weave (5-HS) and reinforced with polyphenylene sulfide matrix (CF/PPS) at different lay angles was numerically investigated. In the modeling studies, experimentally determined Ls_Dyna MAT 58 composite material model parameters and Hashin fracture criteria given in the literature, as well as the contact and control settings used, were shared. In this study, a modeling approach based on (Shell) shell elements was used to further analyze the high-velocity impact response of CF/PPS (carbon fiber reinforced polyphenylene sulfide) thermoplastic composite laminates. This method allows for the separate representation of each layer constituting the laminate structure, enabling more accurate simulation of interlayer interactions. In the model, each layer of the composite was modeled with fully integrated shell elements (Element Formulation 16) using the SECTION_SHELL input, and its layers were defined separately. The shell thickness for a single layer was 0.28125 mm, the thickness value used in the reference study, and a four-node square element was determined as 1 mm for the mesh structure. The composite thickness value was 2.25 mm for all eight layers. Analyses were repeated for different layers and velocities in the study, and the relevant analysis scenario was created. The Fixity Node boundary condition applied to the outer edge of the composite sample was provided by a node set defined on the outer wall of the composite plate; the nodes were fixed in all six degrees of freedom (6-DOF). As can be seen from the velocity vectors, the initial velocity definition within the boundary conditions was made in the negative direction of the X-axis. The relevant velocity values are detailed in the next section. The velocity of the sphere is shown in the negative direction of the X-axis using the INITIAL_VELOCITY_GENERATION card in the LS-DYNA software at different velocities. The analyses were repeated at different velocities. The verification process performed for [0]8, which is specified in the reference source and where the material properties are used, was also planned for this study. In this context, the sphere exit velocity and the damage appearance on the composite panel were obtained. As a result of the analysis, the exit velocity of [0]8 was calculated as 91.8 m/s. The reference experimental result was shared as 89.7 m/s. The successful prediction of the exit velocity and deformation shape of the reference study showed that the analysis model worked correctly. The analyses were repeated within the scope of the study using the said boundary conditions and material model for the main combinations, different velocities and different laying angles (>40 in total). In LS-DYNA, for multi-layer models, the fragment exit velocity and damage to the composite panel were investigated when composite panels were created at different deployment angles ([0]8, [0/90]4, [0/45]4, [±45]4, and [0/45/-45/90]2) and impacted by a 30 mm diameter steel spherical fragment at speeds of 60 and 101.7 m/s. The analysis results showed that, particularly at high speeds (Vi = 101.7 m/s), the effect of the difference in deployment angle on exit velocity was negligible, while the effect at low speeds was relatively greater. The change in the Vr/Vi ratio with the number of layers was obtained for composite structures with [0] and [0/45] orientations at 101.7 impact velocities. It was observed that, as expected, the exit velocity decreased with increasing number of layers in the [0]-degree oriented composite structure, and therefore, the decrease in Vr/Vi continued. On the other hand, the [0/45] structure exhibits a similar behavior with increasing layer count for the same layer count (a layer with a 45-degree orientation was added), but the curve decreases at a faster rate. The two curves converge for low layer counts, and when the layer count is 8, the contribution of the 45-degree orientation layer to ballistic resistance is negligible. As reported in the literature, the presence of 45-degree fibers in the composite structure provides resistance to shear stress, while also providing more uniform distribution of impact energy, thus limiting damage. Considering both the exit velocity and the damage incurred in the composite panel, the presence of a 45-degree laydown angle composite layer generally contributes positively to the overall impact. Considering both the desorption velocity and the damage incurred in the composite panel, [45/0/45/0]2S is considered preferable among the existing samples. Furthermore, increasing the layer thickness suppresses damage formation in the panel at low speeds, resulting in significant improvements in ballistic performance. It is generally reported that symmetrical and quasi-isotropic structures are preferred because they limit impact damage, or in other words, make it more difficult to propagate. It has been suggested that quasi-isotropic arrays can absorb 40% more impact energy than unidirectional arrays. The study concluded that this positive effect is only noticeable when the number of layers is increased; otherwise, fiber orientation and order for the layers are insignificant. This study, conducted using a numerical macro model, showed that the analysis is consistent with the test results and that the damage magnitude can be reasonably estimated. While the [0/90]4 deployment angle numerically reduced the fragment exit velocity to a negligible degree, it is noteworthy that the severity of the damage in both directions (X and Y) is equal. This can be explained by the balance of strength and stiffness in both directions. The findings suggest that layer orientation in thin composite structures may play a role at low speeds, not at high speeds. It was found that the fiber orientations of thin composite panels did not contribute to ballistic resistance under high-velocity impacts. However, it was determined that increasing the number of layers significantly improved ballistic resistance. This behavior is consistent with the general approach outlined in the literature. Another study, in which tests were conducted at high velocities using a steel sphere (12.7 mm), emphasized that laminates using uniaxial fibers exhibited poorer ballistic performance than semi-isotropic panels. This was due to damage occurring at lower energy values and easier crack propagation. On the other hand, studies conducted with semi-isotropic samples with different alignments reported no difference in energy absorption and fracture behavior. Similarly, studies conducted with a 5 mm diameter sphere at a speed between V=150 and 314 m/s determined that the use of woven and cross-ply laminates had no significant effect on ballistic resistance, but the fiber strength used on the back of the panel affected performance. The presence of fibers with a 45-degree orientation within the combination means the placement of an additional layer at a 45-degree angle to the fibers, which are perpendicular to each other along two axes due to the nature of the satin weave. This reduced the severity of fiber damage likely to occur in the high speed contact zone of the spherical fragment. Furthermore, it plays a significant role in preventing delamination damage, particularly due to bending, by providing balanced rigidity to the panel structure. At lower impact speeds (60 m/s), the relatively lower energy transferred to the panel resulted in increased fiber resistance to damage and, consequently, increased bending displacement. This, in contrast to higher speeds, resulted in less matrix damage and more prominent interlayer delamination, ultimately allowing the panel to absorb more energy. At lower speeds, the laying angle yielded significant results. The presence of a layer with a 45-degree laying angle in the resulting layer was observed to have a generally positive effect. For a 32-layer structure, the decrease in exit velocity reached 55% for the [0/45]16 structure containing 45-degree layers. Considering both the exit velocity and the damage incurred in the composite panel, [45/0/45/0]2S was determined to be preferable among the existing samples. The improvement achieved for this combination was approximately 68%. It was understood that increasing the layer thickness suppresses damage formation at low speeds and therefore can provide significant improvements [45/0]8S for the 32-layer structure improved ballistic performance by a factor of 3.1 compared to the [0]32 sample. However, although there was a relative difference between the semi-isotropic, symmetrical composite panels, the improvements achieved were limited.

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