GOALI: Projection Stereolithography of Gradient Viscoelastic Polymer Nanocomposites

聚合物增强复合材料是将增强材料如碳或玻璃纤维或玻璃颗粒与聚合物基材结合在一起，以产生具有增强机械性能的材料的材料。这些材料的使用已经彻底改变了航空航天、汽车和体育用品制造等行业。越来越多的行业转向增材制造或3D打印，以实现具有复杂几何形状的定制组件。然而，立体光刻，一种使用光局部固化（硬化）液体聚合物树脂层以构建固体部分的增材制造工艺，不能成功地生产聚合物增强复合材料。该过程也不能轻易地将材料属性梯度合并到单个构建中。该学术与工业联络资助机会（GOALI）项目旨在通过了解在改进的立体光刻印刷过程中发生的材料加工相互作用，从而克服这些限制，该过程能够将聚合物和纳米颗粒结合起来，以生产打印的聚合物复合材料。该技术的成功将提高可通过立体光刻打印的聚合物材料的性能和范围，从而实现高性能、可定制、功能分级组件的3D打印。这有可能提高美国航空航天、汽车和医疗零部件制造等核心产业的竞争力。Align Technology是一家利用立体光刻技术定制正畸制造工艺的制造商，也是该项目的合作伙伴，参与该项目的学生不仅可以接触到先进的材料科学和制造技术，还可以了解工业挑战和驱动因素。扩展的在线课程将提供给学生和实习工程师，提供灵活的学习机会，随时了解材料科学和制造的新发展。该项目的主要目标是阐明梯度复合聚合物的结构/性能关系，该结构/性能关系是通过基质聚合物的灰度立体光刻，然后用含有纳米颗粒的反应性填料进行膨胀。第二个目标是减少、控制或消除由聚合收缩和溶剂溶胀引起的巨大内应力。后者将通过采用共价适应性矩阵来实现，例如，在自由基存在的情况下重新排列以放松应力的附加-碎片链转移骨架。为实现这些目标，将开展以下工作：1)精确、宏观地表征基体单体到聚合物的转化作为加工条件的函数，以及这种部分转化如何控制填料的膨胀；2)在微米尺度上通过基质的灰色立体光刻技术验证宏观预测，然后是填料的膨胀和聚合；3)验证预测的非均匀印刷纳米复合材料的粘弹性行为；4)证明了可以利用可逆加成-破碎链转移化学来提供块体复合材料的局部应力控制。如果成功，所获得的知识将用于打印和验证具有光致可塑性的打印三元纳米复合材料的预测性能。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。

Polymer reinforced composites are materials that combine reinforcement materials such as carbon or glass fiber, or glass particles with a polymeric base material to produce a material with enhanced mechanical properties. Utilization of these materials has revolutionized industries involved in aerospace, automotive, and sporting goods manufacture. Increasingly, industry is turning to additive manufacturing, or 3D printing, to realize customized components with complex geometries. However, stereolithography, an additive manufacturing process that uses light to locally cure (harden) a liquid polymer resin in layers to build up a solid part, cannot successfully produce polymeric reinforced composites. Nor can the process easily incorporate material property gradients within a single build. This Grant Opportunities for Academic Liaison with Industry (GOALI) project seeks to overcome these limitations by understanding the material processing interactions occurring during a modified stereolithography printing process capable of combining polymers and nanoparticles to produce printed polymer composite materials. Success will advance the performance and range of polymeric materials that can be printed via stereolithography, and in doing so will realize the 3D printing of high performance, customizable, functionally graded components. This has the potential to advance the competitiveness of core US industries involved in the manufacture of aerospace, automotive, and medical components. As Align Technology, a manufacturer utilizing stereolithography in their custom-made orthodontics fabrication process, is a collaborator on this project the students involved in the project will not only be exposed to advanced material science and manufacturing technologies but will also gain an understanding of industrial challenges and drivers. Extended online courses will be made available to students and practicing engineers, providing flexible learning opportunities to keep informed of new developments in materials science and manufacturing.The primary goal of this project is to elucidate the structure/property relationships of gradient composite polymers printed by gray scale stereolithography of a matrix polymer followed by swelling with a reactive filler containing nanoparticles. A secondary goal is to reduce, control or eliminate the large internal stresses caused by polymerization shrinkage and solvent swelling of stereolithographic parts. The latter will be achieved by employing covalent adaptable matrices, e.g. addition-fragmentation chain transfer backbones that rearrange to relax stress in the presence of radicals. To achieve these goals the following tasks will be conducted; 1) precise, macroscopic characterization of matrix monomer-to-polymer conversion as a function of processing conditions and how this partial conversion controls swelling of the filler, 2) validation of the macroscopic predictions on the micron scale via gray-scale stereolithography of the matrix followed by swelling and polymerization of the filler, 3) validation of the predicted viscoelastic behavior of inhomogeneous printed nanocomposites, and 4) demonstration that reversible addition-fragmentation chain transfer chemistry can be leveraged to provide local stress control in bulk composites. If successful the knowledge gained will be used to print and verify the predicted properties of a printed trinary nanocomposite with photo-induced plasticity.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.