Semester

Fall

Date of Graduation

2018

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Ever J. Barbero

Committee Co-Chair

Bruce S. Kang

Committee Member

Bruce S. Kang

Committee Member

Eduardo M. Sosa

Committee Member

Victor H. Mucino

Committee Member

Adi Adumitroaie

Abstract

Carbon fiber reinforced plastics (CFRP) are potential materials for many aerospace and aeronautical applications due to their high specif strength/weight and a low coeffcient of thermal expansion (CTE) resulting in a high long-term stability. Among candidate structures, the re-entry reusable launch vehicles (RLV), the fuel oxidant storage and transportation at cryogenic temperature, space satellites, and aircraft structure (frame, wings, etc...) can be highlighted. However, CFRP are prone to internal damage as a result of high residual stresses and thermal fatigue loading. In this study, micro-cracking damage evolution in laminated composites subjected to monotonic cooling and thermal cyclic loads is developed through a theoretical model. Since matrix-damage predictions requires precise knowledge of the temperature-dependent properties, a detailed methodology to calculate the thermomechanical properties for both matrix and fibers of interest is included. Damage initiation and evolution is studied firstly under quasi-static cooling. The temperature dependence of the critical energy release rate (ERR) is also analyzed. Thermal fatigue of laminated composites is assessed based on low-cycle fatigue tests and the damage mechanisms involved are studied. A Master Paris's law is developed to predict matrix fatigue resistance as function of number of cycles regardless of layup and thermal ratio for both, low and high-cycle tests. Due to physical barriers that implies to perform a complete high-cycle thermal fatigue test, a methodology to simulate a thermal fatigue test using equivalent mechanical cyclic loads is developed to use the former as surrogate from later.

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