CAREER: Fast-Rate Manufacturing of Thermoplastic Polymer Composites with Tailored Microstructure and Performance

这项学院早期职业发展(CALEAR)补助金将支持有助于快速制造具有增强性能的高性能热塑性复合材料的研究，促进美国制造业的科学和技术。高性能热塑性复合材料正在工业中出现，以取代金属，因为这些复合材料具有重量轻、突出的机械性能、化学稳定性和通过热成型在几分钟内即可制造的特点。然而，在冷却速度快的快速过程中，聚合物没有足够的时间形成长链有序(晶体)，这反过来又降低了结晶度水平。提高硬度和强度需要较高的结晶度，但提高韧性需要较低的结晶度。这些相互竞争的性能可以通过控制聚合物的详细结构来优化。这笔赠款支持基础研究，填补了在加工过程中设计热塑性复合材料结晶度以同时实现高刚性、强度和韧性所需的知识空白。纳米材料(NMS)用于控制结晶度，而不使用危险的溶剂，促进了可扩展性。这项研究通过为美国汽车、航空航天和海洋行业配备可扩展的快速制造技术，加快了下一代复合材料的制造，减轻了重量，增加了强度和韧性，有利于美国经济和国家安全。这项研究的跨学科性质为培养STEM领域的下一代高技能工程师和科学家提供了独特的机会，特别是来自女性和代表性较低的少数群体，这进一步加强了美国制造业劳动力的多样化。在快速制造半结晶聚合物复合材料过程中实现的最佳复合材料机械性能需要对结晶形态进行工程设计。这项研究将使在复合材料加工过程中在多个长度尺度上定制半晶复合材料的微观结构的替代能力成为可能。由纤维素纳米晶-石墨烯纳米片组成的纳米材料被用来协同增强和创建分层晶体结构。该项目将通过弥合晶体-非晶区从分子键和力的演化、它们到界面和层间性质的转换以及它们在使用载荷下的变形的知识鸿沟来产生新的信息。本研究利用分子内X射线散射和原位显微技术，辅以密度泛函理论和分子动力学模拟，建立了分子相互作用-半晶微结构-性质的关系。这项研究还解决了从分子键解离到分层的损伤转变。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) grant will support research that contributes to the development of fast-rate manufacturing of high-performance thermoplastic composites with enhanced properties, promoting the US manufacturing science and technology. High-performance thermoplastic composites are emerging in industries to replace metals as these composites offer light weighting, outstanding mechanical properties, chemical stability, and manufacturability within few minutes via thermoforming. However, in fast-rate processes with high cooling rates, there is not sufficient time for the polymer to form long chain orders (crystals) that in turn reduces the crystallinity level. High crystallinity is required for improved stiffness and strength; however, lower crystallinity is desirable to improve toughness. These competing properties can be optimized by control of the detailed structure of the polymer. This grant supports fundamental research that fills the knowledge gap needed to engineer the thermoplastic composite crystallinity during processing to achieve concurrently high stiffness, strength and toughness. Nanomaterials (NMs) are used to control the crystallinity without the use of hazardous solvents, promoting the scalability. The research accelerates the manufacturing of next generation of composites with reduced weight and increased strength and toughness that benefits the US economy and national security by equipping U.S. automotive, aerospace and marine industries with a scalable and fast-rate manufacturing technique. The interdisciplinary nature of this research provides unique opportunities to train the next generation of highly skilled engineers and scientists in STEM fields especially from women and underrepresented minority groups that further enhances the diversification of the US manufacturing workforce.Optimized composite mechanical properties achieved during fast-rate manufacturing of semicrystalline polymer composites require engineering the crystalline morphology. This research will enable alternative capabilities in tailoring the microstructure of semicrystalline composites at multiple length scales during composite processing. Nanomaterials consisting of cellulose nanocrystals-graphene nanoplatelets are used to synergistically reinforce and create a hierarchical crystalline architecture. This project will generate new information by bridging the knowledge gap in the evolution of crystalline-amorphous domains from molecular bonds and forces, their translation to interfacial and interlaminar properties, and their deformation under service load. The research uses in-operando X-ray scattering and in-situ microscopy complemented by density functional theory and molecular dynamics simulations to establish the molecular interactions-semicrystalline microstructure-property relationship. The research also addresses the damage transformation from molecular bonds dissociation to delamination.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.