Gallegos Ivan, Varshney Vikas, Kemppainen Josh, Odegard Gregory M
Michigan Technological University 1400 Townsend Dr Houghton MI 49931 USA
Air Force Research Laboratory, Wright-Patterson Air Force Base 2941 Hobson Way OH 45433 USA.
Nanoscale Adv. 2025 Jan 9;7(6):1582-1595. doi: 10.1039/d4na00824c. eCollection 2025 Mar 11.
Carbon-carbon (C/C) composites are attractive materials for high-speed flights and terrestrial atmospheric reentry applications due to their insulating thermal properties, thermal resistance, and high strength-to-weight ratio. It is important to understand the evolving structure-property correlations in these materials during pyrolysis, but the extreme laboratory conditions required to produce C/C composites make it difficult to quantify the properties . This work presents an atomistic modeling methodology to pyrolyze a crosslinked phenolic resin network and track the evolving thermomechanical properties of the skeletal matrix during simulated pyrolysis. First, the crosslinked resin is pyrolyzed and the resulting char yield and mass density are verified to match experimental values, establishing the model's powerful predictive capabilities. Young's modulus, yield stress, Poisson's ratio, and thermal conductivity are calculated for the polymerized structure, intermediate pyrolyzed structures, and fully pyrolyzed structure to reveal structure-property correlations, and the evolution of properties are linked to observed structural features. It is determined that reduction in fractional free volume and densification of the resin during pyrolysis contribute significantly to the increase in thermomechanical properties of the skeletal phenolic matrix. A complex interplay of the formation of six-membered carbon rings at the expense of five and seven-membered carbon rings is revealed to affect thermal conductivity. Increased anisotropy was observed in the latter stages of pyrolysis due to the development of aligned aromatic structures. Experimentally validated predictive atomistic models are a key first step to multiscale process modeling of C/C composites to optimize next-generation materials.
碳-碳（C/C）复合材料因其隔热性能、耐热性和高强度重量比，成为高速飞行和地球大气层再入应用的理想材料。了解这些材料在热解过程中不断演变的结构-性能关系非常重要，但生产C/C复合材料所需的极端实验室条件使得难以量化其性能。这项工作提出了一种原子建模方法，用于热解交联酚醛树脂网络，并跟踪模拟热解过程中骨架基质不断演变的热机械性能。首先，对交联树脂进行热解，并验证所得的焦炭产率和质量密度与实验值匹配，从而确立该模型强大的预测能力。计算了聚合结构、中间热解结构和完全热解结构的杨氏模量、屈服应力、泊松比和热导率，以揭示结构-性能关系，并将性能的演变与观察到的结构特征联系起来。研究发现，热解过程中树脂的自由体积分数降低和致密化对骨架酚醛基质的热机械性能增加有显著贡献。揭示了以五元环和七元环为代价形成六元碳环的复杂相互作用会影响热导率。由于取向芳香结构的发展，在热解后期观察到各向异性增加。经过实验验证的预测原子模型是C/C复合材料多尺度过程建模以优化下一代材料的关键第一步。
