Kauçuk ağacı (Ficus elastica) yaprağı takviyeli epoksi kompozitin termofiziksel özelliklerinin belirlenmesi

Öz

Bu çalışmada, Ficus elastika yaprakları takviye edilerek epoksi kompozit üretilmekte ve elde edilen kompozitin bazı fiziksel ve kimyasal özellikleri karakterize edilmektedir. Ficus elastika yaprakları 297 ile 149 mikron arasında öğütülmektedir. Dolgu maddesi olarak hazırlanan biyokütle (Ficus elastika) alkali aktivasyonu için % 7'lik sodyum hidroksit (NaOH) çözeltisinde 24 saat bekletilmektedir. Daha sonra distile su ile 3 kez yıkanmakta ve 75 °C sıcaklıkta etüvde 3 saat kurutulmaktadır. Kompozit üretimi, hazırlanan dolgu maddesinin epoksi reçineye kütlece belirli oranlarda takviye edilmesiyle gerçekleştirilmektedir. Ağırlıkça % 0, % 1, % 3, % 5 ve % 7 oranlarında eklenen biyokütle dolgu maddesinin yoğunluk, Shore D sertlik, ısıl iletkenlik katsayısı ve aktivasyon enerjisi üzerine etkisi epoksi kompozitte belirlenmektedir. Elde edilen sonuçlara göre karışımdaki dolgu oranı arttıkça epoksi kompozitin yoğunluğu azalmaktadır. Epoksi kompozitin Shore D sertliği, biyokütle dolgu maddesi ilavesiyle azalmaktadır. Biyokütle takviyesi ile üretilen epoksi kompozitin hem ısıl iletkenlik katsayısını hem de aktivasyon enerjisini düşürmektedir. Ayrıca elde edilen polyester kompozitin kimyasal bağ yapısı Fourier dönüşümlü kızılötesi spektrometre (FTIR) ile incelendiğinde fiziksel bir etkileşimin gerçekleştiği görülmektedir. Taramalı elektron mikroskobu (SEM) görüntülerine göre, Ficus elastika yapraklarının ağırlıkça % 5 ve % 7 takviyesi, epoksi kompozitin yüzey morfolojisini olumsuz etkilemektedir.

Anahtar Kelimeler

• Epoksi kompozit
• Ficus elastica
• Yoğunluk
• Shore D sertlik
• Isıl iletkenlik katsayısı
• Aktivasyon enerjisi

Behaviour of a strip footing adjacent to the existing supported excavation

Öz

This study investigates the results of the numerical analysis on effect of existing supported excavation on ultimate bearing capacity (qult) of strip footing adjacent to supported excavation in sandy soil. The influence of distance (L) between the foundation and the supported excavation was studied as well as the effect of the excavation depth (He). For this purpose, on a full-scale model, a series of numerical calculations were carried out to determine how (L) and (He) affected the behavior of strip foundation. Based on finite element approach, the computer software Plaxis 2D code was utilized. Non-linear hardening soil model, a sophisticated elastoplastic stressstrain constitutive soil model, was used to characterize sandy soil. Based on Mindlin's beam theory, the strip footing and sheet pile wall were identified as elastic beam components with significant flexural rigidity (EI) and axial stiffness (EA). The sheet pile was installed at three different distances (L) away from the face of the strip foundation 1B, 1.5B and 2B, where B is the width of foundation. For each distance, three different excavations (He) were used with dimensions 1B, 1.5B and 2B. The numerical outcomes show that the ultimate bearing capacity (qult) of shallow foundation is decreased when distance between strip foundation and supported excavation is decreased, and vice versa. Additionally, (qult) is reduced as the depth of excavation behind sheet pile wall is increased, and vice versa.

Anahtar Kelimeler

• Finite element methods
• Supported excavation
• Strip foundation
• Sheet pile
• Excavation depth
• Epoksi kompozit
• Ficus elastica
• Yoğunluk
• Shore D sertlik
• Isıl iletkenlik katsayısı
• Aktivasyon enerjisi

Kaynakça

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