Designing New Types of Cellular Hybrids for Lightweighting Applications

考虑到迫在眉睫的经济和环境挑战，一个关键的技术问题是开发新材料，在更低的生态足迹下提高性能——换句话说，找到用更少的资源做更多事情的方法。混合材料的发展为材料属性空间的新领域提供了非常丰富的潜力，混合材料将两种或两种以上的材料结合在一起，以创造单独一种材料无法提供的材料属性组合。通过结合材料和开放空间创造的轻质蜂窝混合动力车在汽车和航空航天领域尤其具有吸引力，可以减少能源消耗。这项NSERC Discovery资助的重点是先进的细胞混合材料，因为细胞混合材料的内部结构提供了一种方法，可以使用基于形状的设计参数来显著改变材料的有效特性，从而使它们能够专门针对结构应用进行定制，其中最小化系统质量是优先考虑的。在这笔拨款中开发的材料将具有更高的性能和更低的环境影响，以便为加拿大航空航天和制造业部门提供竞争优势。航空航天是加拿大的战略部门，根据加拿大航空航天工业协会，为超过80000名加拿大人提供高质量的就业机会，并产生236亿美元的总收入（2008年）。航空航天领域面临的一个主要挑战是制造具有强度、刚度和密度最佳组合的结构材料。微桁架蜂窝材料具有完全三角形的结构，使它们成为最有效的结构方式，通过轻型蜂窝混合材料传输外部施加的载荷。这使得它们的效率比其他轻质蜂窝材料（如金属泡沫）高出一个数量级，并且具有更好的刚度-质量比和强度-质量比。然而，其广泛应用的关键障碍是，最有效的微桁架结构通常不可能由高性能材料制造。我们在之前的发现基金中找到了一种方法来规避这个问题。我们使用增材制造技术创造了一种最高效的聚合物支架，在其上电沉积了超高强度的纳米晶体材料。这些材料目前正在与加拿大领先的航空航天和纳米技术公司合作开发。另一方面，制造业，特别是汽车行业，也需要低成本的方法来生产轻质结构材料，将对环境的影响降到最低。同样由申请人的研究小组发明的随机蜂窝，只需要最少的资本设备来制造：热塑性珠子在加热的盘子之间熔化，然后将它们拉到固定的距离，并让它们冷却。这种被冻结的网状结构可以自发地从金属板上脱键，用一种材料制成热塑性夹层板，其核心和面板完全集成。聚丙烯随机蜂窝的机械性能与商用聚丙烯蜂窝相当，明显高于传统聚丙烯泡沫，另外的优点是它们可以在尖角周围成型。一个衍生公司FlyTechnologies已经成立，将这些材料商业化，我们目前正在与一家领先的汽车零部件制造商合作制造它们。

Given our looming economic and environmental challenges, a key technological issue is to develop new materials that have enhanced performance at a lower ecological footprint - in other words, discovering ways to do more with less. A very rich potential for reaching new regions of material property space comes from the development of hybrids, which combine two or more materials in order to create material property combinations not offered by either material alone. Lightweight cellular hybrids, created by combining material and open space are particularly attractive in order to reduce the energy consumption in the automotive and aerospace sectors. This NSERC Discovery grant is focussed on advanced cellular hybrid materials because the internal architecture of cellular hybrids provides a means for using shape-based design parameters to dramatically alter the effective properties of a material, allowing them to be specifically tailored for structural applications where minimized system mass is a priority. The materials developed in this grant will have enhanced performance and lower environmental impact in order to give a competitive advantage to the Canadian Aerospace and Manufacturing sectors. Aerospace is a strategic sector for Canada, which, according to the Aerospace Industries Association of Canada, provides high-quality employment for over 80000 Canadians and generates total revenues of $23.6 billion (2008). A major challenge for the Aerospace sector is to manufacture structural materials having the best combinations of strength, stiffness, and density. Microtruss cellular materials have fully triangulated architectures making them the most structurally efficient way of having externally applied loads transmitted through a lightweight cellular hybrid. This can make them more than an order of magnitude more efficient than other lightweight cellular materials, such as metallic foams, and enables much better stiffness-to-mass and strength-to-mass ratios. The critical barrier to their widespread application, however, is that optimally efficient microtruss architectures are often impossible to manufacture from high performance materials. We have found a way to circumvent this problem in the previous Discovery Grant. We use additive manufacturing to create an optimally efficient polymeric scaffold, upon which ultrahigh strength nanocrystalline materials are electrodeposited. These materials are currently being developed in partnership with leading Canadian Aerospace and Nanotechnology companies. At the other end of the spectrum, low cost methods to produce lightweight structural materials having minimized environmental impact are also needed for the Manufacturing sector in general and the Automotive sector in particular. Stochastic honeycombs, also invented by the applicant's research group, need only minimal capital equipment to be manufactured: thermoplastic beads are melted between heated plates, which are then pulled to a fixed distance apart and allowed to cool. The frozen-in web structure spontaneously de-bonds from the metal plates, creating a thermoplastic sandwich panel out of a single material with fully integrated core and facesheets. The mechanical properties of polypropylene stochastic honeycombs are comparable to those seen for commercial polypropylene honeycombs and significantly higher than those of conventional polypropylene foams, with the additional advantage that they can be moulded around sharp corners. A spin-off company, FlyTechnologies, has been formed to commercialize these materials and we are currently working with a leading auto parts manufacturer to fabricate them.