GOALI: Modeling of Next Generation Metal-Free Frictionless Materials for the Prevention of Thermal-Mechanical Instabilities

铜和其他重金属被用来在车辆刹车和离合器系统中产生摩擦，以使车轮减速或传递扭矩。摩擦材料配方是复杂的材料系统，也包括各种成分的耐磨性，热稳定性和机械强度。现有的法律法规要求逐步淘汰刹车片中的铜和其他重金属，以减少刹车磨损产生的金属微粒与雨水的接触，并排放到附近的水道中，以限制对水生生物的不利影响。金属的替代品包括石墨、碳纤维、纳米管和陶瓷；然而，它们的引入可能会导致操作安全问题，主要是由于热机械不稳定性导致的摩擦损失。这项学术与工业联络资助机会（GOALI）计划奖励将支持对刹车片部件材料的这些不稳定性进行调查。该项目将提供一种工程分析工具，帮助制造商以经济有效的方式满足法律要求，或者在理想情况下超越未来的法规。无毒摩擦材料替代品的开发将使美国制造商通过提供安全和高性能的制动器和离合器产品来获得全球市场份额。其他使用摩擦材料的行业包括航空航天、石油和天然气、采矿和国防。此外，该项目将支持研究生和本科课程的发展，并为历史上代表性不足的本科生和高中生提供研究和实习机会。在这个项目中，计算模型考虑了基本材料特性和加工条件，将预测与热机械不稳定性（TMI）相关的工程摩擦材料的性能。TMI现象是高速接触下热膨胀、动态和机械应力相互作用引起的结构不稳定现象。TMI的发作可导致裂纹、材料损伤、振动、噪声和机械故障；因此，在下一代无金属摩擦材料系统中研究TMI是势在必行的。这项工作将提高对压缩和填充效应对摩擦材料各向异性性能的基本理解。在这个项目的方法中，多相材料的多尺度模型将结合颗粒或纤维成分的组成和形态对有效机械性能的影响。预测的性能将评估特定材料成分对TMI的敏感性。将开发结合弹性、动力学、接触力学和热屈曲效应的降阶模型。该研究将以计算为主，行业合作伙伴将通过材料特性和临界制动速度和温度的实验测量来验证关键结果。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。

Copper and other heavy metals are used to generate friction in vehicle brake and clutch systems to slow down wheels or transmit torques. Frictional material formulations are complex material systems that also include various ingredients for wear resistance, thermal stability, and mechanical strength. Existing laws and regulations require phase out of copper and other heavy metals in brake pads to reduce contact of metal particulates from brake wear with storm water and discharge into nearby waterways, to limit adverse effects on aquatic life. Substitutions for metals have been suggested to include graphite, carbon fibers, nanotubes, and ceramics; however, their introduction can lead to operational safety issues, primarily through loss of friction due to thermal-mechanical instabilities. This Grant Opportunities for Academic Liaison with Industry (GOALI) Program award will support an investigation of these instabilities in brake pad component materials. The project will deliver an engineering analysis tool facilitating manufacturers a cost-effective way to meet laws or ideally exceed future regulations. The development of non-toxic frictional material alternatives will allow U.S. manufacturers to gain global market share by offering safe and high-performance brake and clutch products. Other industries using friction materials include aerospace, oil and gas, mining, and defense. In addition, this project will support the development of graduate and undergraduate courses and offer research and internship opportunities for historically underrepresented undergraduate and high school students. In this project, computational models accounting for fundamental material characteristics and processing conditions will predict the performance of engineered frictional materials related to thermal-mechanical instabilities (TMI). The TMI phenomenon is a structural instability induced by the interaction between thermal expansion, dynamics, and mechanical stresses under high-speed contact. The onset of TMI can lead to cracks, material damage, vibration, noise, and mechanical failure; therefore, an investigation of TMI in the next generation of metal-free frictional materials systems is imperative. This work will improve fundamental understanding of compression and packing effects on the anisotropic properties of frictional materials. In this project's approach, a multiscale model of heterogeneous materials will incorporate the effects of composition and morphology of particulate or fibrous ingredients on the effective mechanical properties. The predicted properties will evaluate susceptibility of specific material compositions to TMI. Reduced-order models will be developed to combine the effects of elasticity, dynamics, contact mechanics, and thermal buckling. The research will be primarily computational, where the industry collaborators will validate key results through materials characterization and experimental measurements of critical braking speed and temperature.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.