Collaborative Research: Understanding and Controlling the Resistance to Scratching in Alkali-Free Glasses

随着用于LCD/OLED面板的基板玻璃和用于触摸屏计算设备的防损伤保护罩的出现，人类现在比以往任何时候都更多地与玻璃表面进行物理交互。然而，由此产生的刮擦损伤风险仍然是一个关键问题，这严重限制了玻璃在许多应用中的适用性。实际上，由于磨损而产生的残余凹槽往往会影响玻璃的视觉方面，这反过来又会降低其透明度。更重要的是，表面损伤的存在大大降低了玻璃的强度，从而引发了安全问题。为了解决这些问题，本研究旨在揭示铝硅酸钙玻璃中玻璃刮擦的物理现象，这是用于显示应用的无碱玻璃的典型模型。这项工作旨在为开发具有量身定制的抓挠反应的新眼镜提供科学基础。这将有助于促进国家的健康、繁荣和福利，使眼镜能够设计和用于更广泛的应用，具有所需的故障机制，例如，使手持计算设备上的屏幕更耐破碎。通过整合多个学科，包括物理学、材料科学和力学，这项研究将在工程的各个方面培养不同的学生群体，并为形成美国玻璃行业在全球竞争中迫切需要的下一代科学家做出贡献。此外，该奖项将支持两所机构的几项教育和外展活动，例如本科研究、女性和少数族裔学生参与以及高中STEM活动。划痕仍然是玻璃表面损坏的主要类型之一，并且会大大降低玻璃的耐用性。事实上，由于划伤缺陷而产生的径向和中间裂纹在玻璃表面起着应力放大器或奇点的作用，因此，通过降低玻璃的机械强度，对玻璃的结构完整性产生直接影响。然而，到目前为止，玻璃刮擦的力学仍然主要是经验的。为了解决这一知识缺口，计划采用一种综合的多尺度方法，依靠计算和实验任务来揭示无碱铝硅酸盐钙玻璃中的刮擦物理。为此，我们采用多尺度、自下而上的方法，利用分子动力学模拟、结构表征测试和纳米尺度力学实验来建立连续体周动力学模型，旨在解构刮擦过程中每种能量耗散机制的贡献。周围动力学模型的预测将通过划痕试验进行系统验证。多个尺度之间的握手将提供一些新的基础知识，作为阐明玻璃的组成和原子结构如何控制作用于刮擦的每种能量耗散机制的性质和程度的指南。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the advent of substrate glasses for LCD/OLED panels and damage-resistant protective covers for touch-screen computing devices, humans physically interact with glass surfaces now more than ever. However, the resulting risk for scratch-induced damage remains a key concern, which seriously limits glass's suitability to many applications. Indeed, residual troughs resulting from abrasion tend to impact the visual aspect of glasses, which, in turn, deteriorates their transparency. More importantly, the presence of surface damage greatly decreases glass's strength, thereby raising safety issues. To address these concerns, this research aims to reveal the physics of glass scratching in calcium aluminosilicate glasses, an archetypical model for alkali-free glasses used in display applications. This effort seeks to provide a science-based foundation to develop new glasses with tailored responses to scratching. This will contribute towards the advancement of national health, prosperity, and welfare, by allowing glasses to be designed and used for a broader range of applications with desired failure mechanisms, for example allowing screens on handheld computing devices to be more resistant to shattering. By integrating multiple disciplines, including physics, material science, and mechanics, this research will train a diverse group of students in various aspects of engineering and contribute to forming the next generation of scientists that the U.S. glass industry critically needs to compete globally. Additionally, the award will support several educational and outreach activities at both institutions, e.g., undergraduate research, female and minority student participation, and high school STEM events. Scratching remains one of the main types of surface damage and can greatly reduce the durability of a glass. Indeed, the radial and median cracks that often develop as a result of a scratching flaw act as stress amplifiers or singularities on the surface of glasses and, thereby, have a direct influence on glass's structural integrity by decreasing its mechanical strength. Yet, the mechanics of glass scratching has remained chiefly empirical thus far. To address this gap of knowledge, an integrated, multiscale approach relying on both computational and experimental tasks is planned to reveal the physics of scratching in alkali-free calcium aluminosilicate glasses. To this end, we adopt a multiscale, bottom-up approach wherein molecular dynamics simulations, structure characterization tests, and nanoscale mechanical experiments are used to inform continuum peridynamic models with the aim to deconstruct the contribution of each energy dissipation mechanism during scratching. The predictions from peridynamic models will be systematically validated by scratch testing. The handshake between multiple scales will provide some new fundamental knowledge serving as a guide to elucidate how the composition and atomic structure of a glass control the nature and extent of each energy dissipation mechanism that acts upon scratching.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.