UBC Theses and Dissertations
A non-local approach to simulation of damage in composite structures Forghani, Alireza
Fibre reinforced polymers (FRP) are one of the fastest growing materials in advanced structural applications. Due to the complexity and existence of multiple and interactive modes of failure, there is a lack of comprehensive theory that describes the damage behaviour of these materials. The UBC Composite Damage Model (CODAM) is a sub-laminate based model that is designed to simulate the behaviour of laminated composites at the macro (structural) scale. Physical basis and numerical robustness are the main objectives of CODAM development. The original formulation of CODAM that was developed in the mid 1990’s suffers from material objectivity problem that results in spurious dependency of numerical predictions on the choice of the coordinate system. In this thesis, the objectivity issue of the original CODAM is identified and addressed through a new formulation called CODAM2. The new formulation is capable of predicting damage in various laminate lay-ups from quasi-isotropic to unidirectional. It is also capable of simulating the damage-induced orthotropy in the laminate. An orthotropic non-local averaging scheme is developed for CODAM2 to address the localization issue. Compared to isotropic averaging, the orthotropic scheme significantly improves the predicted crack direction and damage pattern in composite laminates. Unlike the conventional isotropic non-local averaging that performs the averaging over a circular (spherical in 3D) zone, in the orthotropic scheme the averaging is performed over an elliptical zone which requires the introduction of two length scales. The performance of CODAM2 equipped with orthotropic averaging is demonstrated through numerical examples. It is shown that the developed model is capable of accurately predicting the damage behaviour in various specimen geometries from sharp-notched to blunt-notched and open-hole specimens. The predictions of the model in terms of load-displacement, crack-tip position, damage height and crack directions agree well with experimental observations and measurements. CODAM2 provides a promising numerical tool to simulate the effect of damage on the behaviour of structures made of laminated composites. This model is computationally efficient and yet relatively simple to understand, calibrate and use in practical applications.
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