Characterization and modeling of damage layer in composite materials

复合材料被认为是对未来技术和生物工程应用影响最大的材料类别之一。为了试图描述这些材料中产生的应变，特别是由于施加的力而跨越不同材料边界的应变，已经开发了各种模型。然而，在这些复合材料的制造过程中，通常会在这些材料中产生缺陷，例如：微裂纹、空隙、不完美的粘附。所产生的这种损伤从来不是均匀的，而是在不同方向上贯穿复合材料而变化。由于这种非均匀损伤，目前的模型在捕捉损伤的变化方面根本不够准确。因此，本提案的目的是提出一种新的更强大的力学模型，以捕捉损伤的变化，验证模型与实验结果，然后检查此力学模型的各种应用的限制有关的复合材料。一旦这一模式得到开发和测试，它将适用于一些相关的应用程序。众所周知，在全关节置换术中，植入物必须用骨水泥牢固地固定在骨上。然而，已经发现的是，随着时间的推移，植入物可能会松动，裂纹可能会形成并通过骨水泥传播。或者，如果水泥没有完全混合，那么裂缝可能从水泥中的微孔缺陷中突出。这将导致骨水泥失效，需要进行翻修手术。因此，为了改善骨水泥的机械和物理性能，将添加剂材料作为增强相结合到骨水泥中是有益的。因此，对于医学界来说，有一种方法来验证引入小于人类头发宽度的碳纤维是否可以防止裂纹生长，总体目标是减少植入物运动和翻修手术，这一点非常重要。这项研究的最终应用涉及研究嵌入软材料（如凝胶，乳膏或生物组织）中的流体填充结构。这项工作的动机源于软组织由具有均匀或不均匀刚度的弹性材料组成的事实。在这个前提下，诸如充满液体的器官或囊肿之类的结构通常在模型模拟中被忽略，即使它们的存在对周围组织如何变形具有相当大的影响。

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.