Characterization and modeling of damage layer in composite materials

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Composite materials are considered to be one of the material classes that will have the greatest impact for future technologies and bioengineering applications. In an effort to try and describe the strains that are developed in these materials and especially across different material boundaries as a result of applied forces various models have been developed. However, during the manufacturing process of these composite materials it is often the case that imperfections such as: microcraks, voids, imperfect adhesions are developed within these materials. This damage that is developed is never uniform but varies through out the composite material in different directions. As a result of this non-uniform damage the current models are simply not accurate enough in capturing the variability in damage. Thus, the objective of this proposal is to propose a new more robust mechanical model to capture the variability in damage, validate the model with experimental results and then subsequently examine the limits of this mechanical model for various applications related to composite materials. Once this model has been developed and tested it will applied to a number of relevant applications. It is well known that during total joint replacement the implant must be securely fashioned to the bone with bone cement. However, what has been found to happen is that over time the implant can loosen and a crack can form and propagate through out the cement. Alternatively, if the cement is not throughly mixed then cracks can eminate from tiny pore defects in the cement. This will lead to failure of the cement and will require revision surgery. Consequently, to improve the mechanical and physical behavior of bone cement, incorporating additive materials as reinforcing phases to the bone cement is beneficial. Hence, it is of significant importance to the medical community to have a method to validate whether the introduction of carbon fibres that are smaller than the width of a human hair can prevent crack growth with the overall goal of reducing implant motion and revision surgery. The final application of this research involves investigating fluid filled structures that are embedded within soft materials such as gels, creams or biological tissues. The motivation for this work stems from the fact that soft tissue is made up of elastic material having either uniform or non-uniform stiffness. With this premise, structures such as fluid filled organs or cysts are often ignored in model simulations even though their presence has a considerable impact on how the surrounding tissue deforms.