Semester

Fall

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Ever J. Barbero

Committee Co-Chair

Victor H. Mucino

Committee Member

Eduardo M. Sosa

Abstract

A constitutive model to predict the stiffness and coefficient of thermal expansion (CTE) reduction due to transverse matrix cracking in laminated composite structures is implemented as a user subroutine in Abaqus. The assumptions of the model are a symmetric laminate under in-plane loads and linear distribution of intralaminar shear stresses. The model was latter validated using 3D finite element analysis (FEA) in a repetitive unit volume for a wide interval of crack densities and for several laminates, and the difference was found to be within 3%. The FEA, the model and classical laminate theory all converged to the same values of stiffness and CTE for the limiting cases of intact and completely damaged material. The user subroutine was then used to predict the crack density, longitudinal elastic modulus and Poisson's ratio as a function of strain or stress for laminates reported in the literature. For this purpose, the energy release rate, GIc, a material property not accessible through experimentation, was adjusted by a minimization algorithm. The influence of the choice of the damage activation function (interacting or not interacting) in the convergence was studied as well, and it was found that the non-interacting damage function converges faster to the desired value of energy release rate, when compared to the interacting one. Overall, the model is able to predict well damage initiation and evolution for e-glass and carbon fiber composites of arbitrary symmetric stacking sequence.

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