聚苯并恶嗪树脂低固化收缩成因的计算机模拟研究
Understanding the Origin of the Low Cure-Shrinkage of Polybenzoxazine Resin by Computational Simulation
摘要：
热固性树脂基复合材料广泛应用于航空航天工业，主要是由于其高的刚度重量比和强度重量比。在纤维复合材料中使用热固性树脂的主要问题是在固化过程中由树脂化学收缩形成的工艺诱导的残余应力。复合材料内的这些残余应力最终导致最终产品的耐久性降低和残余变形。聚苯并恶嗪（PBZ）聚合物树脂在固化过程中表现出接近零的体积收缩。虽然PBZ的低收缩率在降低工艺引起的残余应力方面是有希望的，但关于物理原因知之甚少。在这项工作中，分子动力学（MD）模拟进行与反应力场预测的物理性能（凝胶化点，网络的演变，质量密度，体积收缩）和机械性能（体积模量，剪切模量，杨氏模量，泊松比，屈服强度）作为交联密度的函数。本文使用模拟的PBZ树脂的实验测量来验证MD模拟程序。本研究的结果是用来提供一个物理理解的零收缩现象PBZ。这些信息也是PBZ复合材料未来工艺建模工作的关键输入。
英文摘要：
Thermoset resin-based composite materials are widely used in the aerospace industry, mainly due to their high stiffness-to-weight and strength-to-weight ratios. A major issue with the use of thermoset resins in fiber composites is the process-induced residual stresses that are formed from resin chemical shrinkage during the curing process. These residual stresses within the composite material ultimately result in reduced durability and residual deformations of the final product. Polybenzoxazine (PBZ) polymer resins have demonstrated near-zero volumetric shrinkage during the curing process. Although the low shrinkage of PBZ is promising in terms of reduced process-induced residual stresses, little is known about the physical causes. In this work, Molecular Dynamics (MD) simulations are performed with a reactive force field to predict physical properties (gelation point, evolution of network, mass density, volumetric shrinkage) and mechanical properties (Bulk modulus, Shear modulus, Young's modulus, Poisson's ratio, Yield strength) as a function of crosslinking density. The MD modeling procedure is validated herein using experimental measurements of the modeled PBZ resin. The results of this study are used to provide a physical understanding of the zero-shrinkage phenomenon of PBZ. This information is also a critical input to future process modeling efforts for PBZ composites.
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