Embrittlement mechanisms in polymer lenses for protective eyewear

眼睛和面部的防护材料需要透明但耐冲击，这限制了 材料.聚碳酸酯（PC）由于其容量大，一直是护目镜，镜片和遮阳板的首选 以通过延展性变形吸收冲击的机械能。最近，更先进的透明 聚合物已经出现。Revision特别感兴趣的材料是透明聚酰胺（PA）。 在Revision进行的弹道测试表明，它们在抗冲击性方面上级PC。但他们 我还注意到，对这种材料的第二次冲击往往会引发脆性破坏， 抗冲击性差。这种行为是有问题的，因为现代透明眼镜需要多次击中， 能力的还显示沉积功能性涂层以增加硬度和防止起雾 使情况变得更糟，材料从一开始就表现出脆性行为和差的抗冲击性 冲击本项目的目的是调查可能的原因脆化的透明 在第二次注射时和/或在沉积硬涂层、防雾涂层或这两者时使用聚酰胺。几种可能 将研究脆化的原因，包括由冲击波引起的微观结构的变化， 第一次冲击产生的残余应力，应力波引起的表面裂纹扩展，塑性约束 硬涂层的变形。在项目结束时，我们将向Revision提供建议。 如何减轻或完全抑制上述情景的影响。巴特拉在麦吉尔的团队 在材料表征、微观结构、材料测试、力学和机械性能方面具有专业知识 调查此问题所需的行为。该项目将大大有利于我们的合作伙伴，修订， 提高他们对透明聚酰胺的认识和应用。通过该项目，修订版将不会 不仅获得新的和独特的知识，在这些材料，它也将培训其工程师与新的知识， 数据最后，通过这个项目培训的博士后将加入加拿大的劳动力， 弹道材料方面的技术工作知识，使他在就业市场上极具竞争力。

Protective materials for eyes and face need to be transparent yet impact resistant, which restrict the choice of materials. Polycarbonate (PC) has been a favored choice for goggles, lenses and visors because of its capacity to absorb mechanical energy for impact by ductile deformations. Recently, more advanced transparent polymers have emerged. The materials of particular interest for Revision are transparent polyamides (PA). Ballistic tests at Revision revealed that they were superior to PC in terms of impact resistance. However, they also noted that a second impact on this material often triggered a brittle type of failure associated with a very poor impact resistance. This behavior is problematic, because modern transparent eyewear requires multi-hit capabilities. It also appeared that the deposition of functional coatings to increase hardness and prevent fogging make the situation worse, the material exhibiting brittle behavior and poor impact resistance from the very first impact. The objective of this project is to investigate possible causes for the embrittlement of transparent polyamides on second shot and/or upon deposition of a hard coating, anti-fog coating or both. Several possible causes for the embrittlement will be investigated including changes in microstructure induced by shock waves, residual stresses from first impact, propagation of surface cracks from stress waves, confinement of plastic deformations by the hard coating. Towards the end of the project we will provide recommendations to Revision on how to mitigate or totally suppress the effects of the scenarios presented above. Barthelat's team at McGill has the expertise in material characterization, microstructure, materials testing, mechanics and mechanical behavior required to investigate this problem. This project will significantly benefit our partner, Revision, in advancing their knowledge and application of transparent polyamides. Through this project Revision will not only gain new and unique knowledge in those materials, it will also train its engineers with new knowledge and data. Finally the postdoc trained through this project will join the Canadian work force with a scientific and technical working knowledge in ballistic materials, making him highly competitive on the job market.