In Situ Calibration of Cohesive Zone Models for Composite Damage

复合材料的设计过程仍然高度依赖于机械测试。这是耗时且昂贵的。一个更有效的过程将涉及更多地使用建模和仿真来优化设计。其核心问题在于缺乏良好的模型，确定复合材料结构的强度和耐久性的破坏过程。这些过程是复杂的，并发生在几个长度尺度。一个有效的建模方法将能够在多个长度尺度上工作，但适合在结构设计和分析中常用的数值框架（通常是有限元模型）。凝聚带模型（CZM）最近受到了相当大的关注，因为它提供了一种数值上有效的方法来满足这些目标。它们很容易嵌入到有限元模型中，但可以捕获在几个长度尺度上发生的一些关键机制。然而，在大多数情况下，这些模型尚未独立校准，因此预测能力有限。该建议旨在通过应用一种新的实验技术，高分辨率X射线层析成像，结合反渗透剂或颗粒来增强对比度，以获得必要的数据，以允许独立校准的内聚区models.High分辨率X射线层析成像可以允许亚微位移和空间分辨率和应变分辨率小于100微应变。这应该是足够的分辨率，以捕捉损伤修改的应变和位移场相关的确定复合材料结构的失败。如此高的分辨率需要使用高能同步辐射，因此这项工作将与格勒诺布尔的欧洲同步辐射设施合作进行。较低分辨率的工作（1-10微米分辨率）将在南安普顿大学进行实验室规模的断层成像仪将部分由本grant. To购买评估的凝聚带模型的有效性，现有的模型创建的合作者在罗克韦尔科学公司将被使用。这可以根据实验应变映射的结果进行修改或实质性修改。缺口尖端损伤和缺口强度的问题将得到解决，因为它代表了一个关键的测试情况下，迄今已被证明难以建模，而不诉诸校准的数据集建模，这相当于经验曲线拟合。这项工作将与SP系统公司（英国领先的复合材料供应商）和空中客车英国公司（英国领先的复合材料和结构设计商和用户）一起进行。

The process for designing with composite materials remains highly dependent on mechanical testing. This is time consuming and expensive. A more efficient process would involve increased use of modeling and simulation to iterate on designs. The core problem lies in the lack of good models for the failure processes that determine the strength and durability of composite structures. These processes are complicated and occur at several lengthscales. An effective modeling approach would be capable of working across multiple lengthscales and yet fit within the numerical frameworks (typically finite element models) commonly used in structural design and analysis. Cohesive zone models (CZM) have recently received considerable attention as offering a numerically efficient means of meeting these aims. They are readily embedded in finite element models, and yet can capture some of the key mechanisms occurring at several lengthscales. However, for the most part these models have not been independently calibrated and therefore have limited predictive capability. This proposal aims to address this limitation by applying a novel experimental technique, high resolution X-ray tomography, in combination with penetrants or particles to enhance contrast, to obtain the necessary data to allow independent calibration of cohesive zone models.High resolution X-ray tomography can allow sub-micro displacement and spatial resolution and strain resolution of less than 100 microstrain. This should be more than sufficient resolution to capture the damage-modified strain and displacement fields relevant to determining failure of composite structures. Such high resolution requires use of high-energy synchrotron radiation, so this work will be conducted in collaboration with the European Synchrotron Radiation Facility at Grenoble. Lower resolution work (1-10 micron resolution) will be performed with a lab-scale tomographic imager at Southampton University to be partially purchased by this grant.In order to evaluate the efficacy of a cohesive zone model, an existing model created by collaborators at Rockwell Scientific will be used. This can be modified or substantially revised depending on the results of the experimental strain mapping. The problem of notch-tip damage and notched strength will be tackled as it represents a key test case that has hitherto proven difficult to model without resorting to calibration on the data set being modeled, which amounts to empirical curve fitting. The work will be performed in conjunction with SP systems, a leading UK supplier of composite materials and Airbus UK a leading UK designer and user of composite materials and structures.