Termal koruma sistemleri için ablatif polimerik kompozitlerin üretimi ve karakterizasyonu
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Dosyalar
Tarih
2023
Yazarlar
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Yayıncı
Bursa Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Havacılık, uzay ve nükleer mühendislik gibi birçok alanda yoğun şekilde kullanılan malzemeler ciddi sıcaklıklara ve basınçlara maruz kalmaktadır. Havacılık ve uzay alanında kullanılan atmosfere yeniden giriş uzay araçları, füzeler ve uzay kapsülleri gibi araçlar atmosfere yeniden giriş sırasında şiddetli aerodinamik ısınmalar sonucunda araçların yüzeyinin yüksek sıcaklıklara ve basınca maruz kalmasına neden olmaktadır. Termal koruma sistemleri (TPS), uzay aracı yüzeyinde oluşan aerodinamik ısınmanın uzay aracının içerisine taşınmasını ve yüklere (insan ve kargo) ulaşmasını engelleyerek termal bir bariyer görevi görmektedir. Bu tez çalışmasında, termal koruma sistemlerinde kullanılan ablatif polimerik kompozitler için matris malzemesi geliştirilerek kompozitler üretilmiştir. Üretilen kompozitlerin ablasyon özellikleri ve ablasyon mekanizmaları incelenmiştir. Resorsinol-formaldehit reçinesi (RR), farklı ağırlık yüzdelerinde fenilboronik asit ile modifiye edilerek ve farklı ağırlık yüzdelerinde titanyum diborür (TiB2) ile dolgulanarak matris malzemeleri geliştirilmiştir. Matris malzemeleri, DSC (Diferansiyel taramalı kalorimetre), EDS (Enerji dağılımlı spektroskopi), FTIR (Fourier dönüşümlü kızılötesi spektroskopisi), NMR (Nükleer manyetik rezonans), SEM (Taramalı elektron mikroskobu), TGA (Termogravimetrik analiz), XPS (X-Işını fotoelektron spektroskopi) ve XRD (X-ışını kırınım) yöntemleriyle karakterize edilmiştir. Geliştirilen fenilboronik asit modifiyeli resorsinol-formaldehit reçinelerinin (RRB) yapısında yeni boronat bağları yer almıştır ve piroliz reaksiyonları sırasında boronat bağları, B2O3 (dibor trioksit) yapısına dönüşmüştür. Matris malzemesinin borla modifiyelenmesi ve TiB2 ile dolgulanması termal dayanımı ve kömür verimini arttırmıştır. RR polimerinin kömür verimi 1000 °C'de %47,9 iken, ağırlıkça %6 fenilboronik asit ile modifiyelenerek ve ağırlıkça %20 TiB2 ile dolgulanarak hazırlanan matris malzemesinin (RRBT20) kömür verimi %88,2 değerine çıkarılmıştır. Hazırlanan matris malzemeleri poliakrilonitril (PAN) temelli iğne ile delinmiş karbon fiber keçelere emprenye edilerek kompozitler üretilmiştir. Kompozitlere üç nokta eğme testi yapılmıştır ve reçinenin borla modifiye edilmesi ve dolgulanması kompozitlerin eğilme mukavemetlerini arttırmıştır. Kompozitlerin ablasyon özellikleri, oksiasetilen alev testi kullanılarak belirlenmiştir. Kompozitlerdeki titanyum diborür içeriğinin artması ile ablasyon direnci arttırılmıştır. Saf RR matrisi ile hazırlanan kompozitin ortalama doğrusal ablasyon oranı (DAO), kütle ablasyon oranı (KAO) ve kömürleşme oranı (KO) sırasıyla 0,0273 mm/sn, 0,0652 g/sn ve 0,2120 mm/sn iken, en iyi ablasyon direncini sağlayan K-RRBT20 kompozitinin DAO, KAO ve KO değerleri sırasıyla 0,0053 mm/sn, 0,0195 g/sn ve 0,0543 mm/sn değerine düşürülmüştür. Kompozitlerin ablasyon mekanizmaları, oksiasetilen alevine maruz kaldıktan sonra oluşan kömür tabakalarının EDS (Enerji dağılımlı spektroskopi), SEM (Taramalı elektron mikroskobu), XPS (X-Işını fotoelektron spektroskopi) ve XRD (X-ışını kırınım) analizlerinden elde edilen çıkarımlarla türetilmiştir. Kompozitlerdeki titanyum diborür, yüksek sıcaklık koşulları altında oksidasyona uğrayarak B2O3 (dibor trioksit) ve TiO2 (titanyum dioksit) yapılarını oluşturmuştur. Karbon fiberin ve reçinenin yüksek sıcaklıkta karbon kömürüne dönüşmesi ve TiO2 ile reaksiyona girmesiyle TiC (titanyum karbür) oluşmuştur. Oluşan bu yeni yapılar kompozitlerin ablasyon direncinin artmasına ve kompozitin ısı bariyeri oluşturmasına olanak sağlamıştır. Kompozitlerin oksiasetilen testinde ön yüzeylerine gelen 2650-2700 °C sıcaklık değerine karşın arka yüzey sıcaklıkları 24,8-26,8 °C aralığında kalarak ısı bariyeri sağlamıştır.
Materials used extensively in many fields such as aerospace and nuclear engineering are exposed to serious temperatures and pressures. Vehicles such as re-entry space vehicles, missiles and space capsules used in the field of aerospace cause the surface of the vehicles to be exposed to high temperatures and pressure as a result of severe aerodynamic heating during re-entry into the atmosphere. Thermal protection systems (TPS) act as a thermal barrier by preventing the aerodynamic heat generated on the surface of the spacecraft from being carried inside the spacecraft and reaching the payloads (humans and cargo). In this thesis, composites were produced by developing matrix material for ablative polymeric composites used in thermal protection systems. The ablation properties and ablation mechanisms of the produced composites were investigated. Matrix materials have been developed by modifying resorcinol-formaldehyde resin (RR) with different weight percentages of phenylboronic acid and filling with titanium diboride (TiB2) at different weight percentages. Matrix materials were characterized by DSC (Differential scanning calorimetry), FTIR (Fourier Transform Infrared Spectroscopy), NMR (Nuclear magnetic resonance), SEM (Scanning electron microscopy), TGA (Thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy) and XRD (X-Ray diffraction) methods. New boronate bonds were included in the structure of the developed phenylboronic modified resorcinol-formaldehyde resins (RRB), and boronate bonds were transformed into B2O3 structure during the pyrolysis reactions. Modifing with boron and filling with TiB2 of the matrix material increased the thermal stability and char yield. While the char yield of the RR polymer was 47.9% at 1000 °C, the char yield of the matrix material (RRBT20), which was prepared by modifying with 6% wt of phenylboronic acid and filling with 20% by weight of TiB2, was increased to 88.2%. Composites were produced by impregnating the prepared matrix materials into polyacrylonitrile (PAN) based needle punched carbon fiber felts. Composites were subjected to a three-point bending test, modification of the resin with boron and filling increased the flexural strength of the composites. The ablation properties of the composites were determined using the oxyacetylene flame test. Increasing the titanium diboride content in the composites increased the ablation resistance. While the mean linear ablation rate (LAR), mass ablation rate (MAR) and charring rate (CR) of the composite prepared with pristine RR matrix provided values of 0.0273 mm/sec, 0.0652 g/sec and 0.2120 mm/sec, respectively, the LAR, MAR and CR values of the K-RRBT20 composite, which provides the best ablation resistance, were reduced to 0.0053 mm/sec, 0.0195 g/sec and 0.0543 mm/sec, respectively. The ablation mechanisms of the composites were derived from the inferences obtained from EDS (Energy dispersive spectroscopy), SEM (Scanning electron microscopy), XPS (X-Ray photoelectron spectroscopy) and XRD (X-ray diffraction) analyzes of char layers formed after exposure to oxyacetylene flame. Titanium diboride in the composites oxidized under high temperature conditions, resulting in the formation of B2O3 (diboron trioxide) and TiO2 (titanium dioxide) structures. TiC (titanium carbide) was formed by the conversion of carbon fiber and resin into carbon char at high temperature and then reacting with TiO2. These new structures have enabled the ablation resistance of the composites to increase and the composite to form a heat barrier. Despite the 2650-2700 °C temperature value on the front surfaces of the composites in the oxyacetylene test, the back surface temperatures remained in the range of 24.8-26.8 °C, providing a heat barrier.
Materials used extensively in many fields such as aerospace and nuclear engineering are exposed to serious temperatures and pressures. Vehicles such as re-entry space vehicles, missiles and space capsules used in the field of aerospace cause the surface of the vehicles to be exposed to high temperatures and pressure as a result of severe aerodynamic heating during re-entry into the atmosphere. Thermal protection systems (TPS) act as a thermal barrier by preventing the aerodynamic heat generated on the surface of the spacecraft from being carried inside the spacecraft and reaching the payloads (humans and cargo). In this thesis, composites were produced by developing matrix material for ablative polymeric composites used in thermal protection systems. The ablation properties and ablation mechanisms of the produced composites were investigated. Matrix materials have been developed by modifying resorcinol-formaldehyde resin (RR) with different weight percentages of phenylboronic acid and filling with titanium diboride (TiB2) at different weight percentages. Matrix materials were characterized by DSC (Differential scanning calorimetry), FTIR (Fourier Transform Infrared Spectroscopy), NMR (Nuclear magnetic resonance), SEM (Scanning electron microscopy), TGA (Thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy) and XRD (X-Ray diffraction) methods. New boronate bonds were included in the structure of the developed phenylboronic modified resorcinol-formaldehyde resins (RRB), and boronate bonds were transformed into B2O3 structure during the pyrolysis reactions. Modifing with boron and filling with TiB2 of the matrix material increased the thermal stability and char yield. While the char yield of the RR polymer was 47.9% at 1000 °C, the char yield of the matrix material (RRBT20), which was prepared by modifying with 6% wt of phenylboronic acid and filling with 20% by weight of TiB2, was increased to 88.2%. Composites were produced by impregnating the prepared matrix materials into polyacrylonitrile (PAN) based needle punched carbon fiber felts. Composites were subjected to a three-point bending test, modification of the resin with boron and filling increased the flexural strength of the composites. The ablation properties of the composites were determined using the oxyacetylene flame test. Increasing the titanium diboride content in the composites increased the ablation resistance. While the mean linear ablation rate (LAR), mass ablation rate (MAR) and charring rate (CR) of the composite prepared with pristine RR matrix provided values of 0.0273 mm/sec, 0.0652 g/sec and 0.2120 mm/sec, respectively, the LAR, MAR and CR values of the K-RRBT20 composite, which provides the best ablation resistance, were reduced to 0.0053 mm/sec, 0.0195 g/sec and 0.0543 mm/sec, respectively. The ablation mechanisms of the composites were derived from the inferences obtained from EDS (Energy dispersive spectroscopy), SEM (Scanning electron microscopy), XPS (X-Ray photoelectron spectroscopy) and XRD (X-ray diffraction) analyzes of char layers formed after exposure to oxyacetylene flame. Titanium diboride in the composites oxidized under high temperature conditions, resulting in the formation of B2O3 (diboron trioxide) and TiO2 (titanium dioxide) structures. TiC (titanium carbide) was formed by the conversion of carbon fiber and resin into carbon char at high temperature and then reacting with TiO2. These new structures have enabled the ablation resistance of the composites to increase and the composite to form a heat barrier. Despite the 2650-2700 °C temperature value on the front surfaces of the composites in the oxyacetylene test, the back surface temperatures remained in the range of 24.8-26.8 °C, providing a heat barrier.
Açıklama
Anahtar Kelimeler
Kimya Mühendisliği, TECHNOLOGY::Chemical engineering
