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Modeling of Thermo-Mechanical Degrad...

Konduri, Gopala Krishna Teja.

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Modeling of Thermo-Mechanical Degradation of Polymer Matrix Composites at High Temperatures.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Modeling of Thermo-Mechanical Degradation of Polymer Matrix Composites at High Temperatures./
作者:	Konduri, Gopala Krishna Teja.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
面頁冊數:	183 p.
附註:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
標題:	Mechanical engineering. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30246378
ISBN:	9798379660819

Modeling of Thermo-Mechanical Degradation of Polymer Matrix Composites at High Temperatures.
Konduri, Gopala Krishna Teja.

Modeling of Thermo-Mechanical Degradation of Polymer Matrix Composites at High Temperatures. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 183 p.

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Thesis (Ph.D.)--The University of Arizona, 2023.

This item must not be sold to any third party vendors.

Carbon fiber reinforced polymer (CFRP) composites are used extensively in aerospace structures due to their high stiffness, strength and low weight. However, these materials have low operational temperatures as their properties are adversely affected by heating. At temperatures above glass transition chemical pyrolysis reactions occur in the polymer leading to the formation of a carbonaceous char residue, and pores filled with pyrolysis gasses. This process, also known as thermal decomposition, leads to an irreversible loss of mass and deterioration of mechanical and thermal properties of the material. Characterizing the behavior of these materials at high temperatures enables the design of structures for severe loading conditions such as lightning strike, laser ablation and fire.In this work micromechanics-based approach is used to predict the effective thermal and mechanical properties of AS4/3501-6 CFRP composite while thermal decomposition occurs. Arrhenius decay law from chemical kinetics is used to create a physics based model to account for the formation of new phases (char and pores) and mass loss in the material. This model enables to create temperature dependent multi-phase Representative Volume Elements (RVE) of CFRP composite at any stage of thermal decomposition. The RVE generated are densely packed with particles randomly distributed and oriented without any directional dependencies.Finite element analysis (FEA) based numerical homogenization procedures for calculating the effective thermal conductivity, specific heat, elastic moduli and coefficient of thermal expansion are developed. The developed procedures are used to calculate the effective properties of AS4/3501-6 composite as a function of temperature and heating rate until the thermal decomposition of the polymer is completed. The calculated effective properties are compared with experimental data from literature and theoretical bounds for multiphase materials.The effects of the decomposition reactions, material phase changes, mass loss and the pressure exerted by the pyrolysis gases trapped in the pores of the material on the effective properties of AS4/3501-6 composite are investigated. Decomposition reactions in 3501-6 polymer are exothermic causing additional heat generation in the material during phase change. A nonlinear transient heat transfer problem is solved at the micro-scale to account for this additional heat generation in the calculation of the effective specific heat.The developed micromechanics based material model is implemented into an FEA analysis of a lightning strike on a CFRP composite. The multi-physic interaction of a lightning current channel with a conductive CFRP laminate is modeled. The model features the effect of Joule heating, spatial and temporal evolution of the lightning current channel, temperature and heating rate dependent material properties, fiber sublimation and material removal. The surface recession and thermal damage of AS4/3501-6 composite subjected to a lightning strike using the developed micromechanics material model and empirical material models from literature is compared with experimental data.

ISBN: 9798379660819Subjects--Topical Terms:

649730
Mechanical engineering.
Subjects--Index Terms:

Carbon fiber reinforced polymer

Modeling of Thermo-Mechanical Degradation of Polymer Matrix Composites at High Temperatures.
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500 $a Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
500 $a Advisor: Zhupanska, Olesya I.
502 $a Thesis (Ph.D.)--The University of Arizona, 2023.
506 $a This item must not be sold to any third party vendors.
520 $a Carbon fiber reinforced polymer (CFRP) composites are used extensively in aerospace structures due to their high stiffness, strength and low weight. However, these materials have low operational temperatures as their properties are adversely affected by heating. At temperatures above glass transition chemical pyrolysis reactions occur in the polymer leading to the formation of a carbonaceous char residue, and pores filled with pyrolysis gasses. This process, also known as thermal decomposition, leads to an irreversible loss of mass and deterioration of mechanical and thermal properties of the material. Characterizing the behavior of these materials at high temperatures enables the design of structures for severe loading conditions such as lightning strike, laser ablation and fire.In this work micromechanics-based approach is used to predict the effective thermal and mechanical properties of AS4/3501-6 CFRP composite while thermal decomposition occurs. Arrhenius decay law from chemical kinetics is used to create a physics based model to account for the formation of new phases (char and pores) and mass loss in the material. This model enables to create temperature dependent multi-phase Representative Volume Elements (RVE) of CFRP composite at any stage of thermal decomposition. The RVE generated are densely packed with particles randomly distributed and oriented without any directional dependencies.Finite element analysis (FEA) based numerical homogenization procedures for calculating the effective thermal conductivity, specific heat, elastic moduli and coefficient of thermal expansion are developed. The developed procedures are used to calculate the effective properties of AS4/3501-6 composite as a function of temperature and heating rate until the thermal decomposition of the polymer is completed. The calculated effective properties are compared with experimental data from literature and theoretical bounds for multiphase materials.The effects of the decomposition reactions, material phase changes, mass loss and the pressure exerted by the pyrolysis gases trapped in the pores of the material on the effective properties of AS4/3501-6 composite are investigated. Decomposition reactions in 3501-6 polymer are exothermic causing additional heat generation in the material during phase change. A nonlinear transient heat transfer problem is solved at the micro-scale to account for this additional heat generation in the calculation of the effective specific heat.The developed micromechanics based material model is implemented into an FEA analysis of a lightning strike on a CFRP composite. The multi-physic interaction of a lightning current channel with a conductive CFRP laminate is modeled. The model features the effect of Joule heating, spatial and temporal evolution of the lightning current channel, temperature and heating rate dependent material properties, fiber sublimation and material removal. The surface recession and thermal damage of AS4/3501-6 composite subjected to a lightning strike using the developed micromechanics material model and empirical material models from literature is compared with experimental data.
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