1、背景与介绍
纤维增强树脂基复合材料(FRP)已越来越多地用作建筑和民用基础设施中的增强和承载构件。在服役过程中，长期不断变化的环境和荷载条件会导致复材的性能退化，这与纤维/基体界面的退化和脱粘高度相关。分子模拟以原子为基本单元构建分子结构，准确表征分子间相互作用，能够对其在不同环境和荷载作用下，微观结构和材料特性随时间的演变进行可视化，被认为是研究纤维/基体界面退化机制的有效手段。本文综述了近年来在潮湿、盐水、高温环境以及各种荷载作用下纤维/基体界面的分子模拟研究，探究了界面的退化机制。
图1. 承受环境和荷载作用的FRP复材应用：(a)FRP结构；(b)外部荷载通过纤维/基体界面传递；(c)界面的分子结构
玻璃纤维(GF)/和碳纤维(CF)因其高刚度和强度、良好的绝缘性能以及合理的价格而成为复材应用中使用最广泛的纤维。本节综述了界面模型中的玻璃纤维和碳纤维的建模方法(图2(a))、树脂的交联固化过程(图2(c))，水环境、盐水环境和高温环境的模拟仿真，以及描述分子间相互作用的力场选择。其中，纤维/基体界面通常由纳米级纤维和树脂基体组成的双层或夹层界面表示，如图2(b)所示。图2. (a)纤维外层由代表玻璃纤维(GF)的二氧化硅单元或代表碳纤维(CF)的多个平行石墨片组成，并涂有表面处理的偶联剂；(c)树脂单体和固化剂进行交联聚合后，与纤维粘合在一起形成(b)纤维/基体界面
a) 综述了不同环境和荷载作用下玻璃纤维基体界面、碳纤维/基体界面的特性。
表1. 不同环境和荷载作用下玻璃纤维/基体界面的退化情况
表2. 不同环境和荷载作用下碳纤维/基体界面的退化情况b) 综述了碳纤维/基体界面在不同的外部荷载的应力-应变曲线和微观结构变化，包括等速剥离荷载(图3)、等速剪切荷载(图4)、恒定荷载(图5-6)。
图3.等速剥离荷载下碳纤维/环氧树脂界面的应力-应变曲线和微观结构变化
图4.等速剪切荷载下碳纤维/环氧树脂界面的应力-应变曲线和微观结构变化
图5. 恒定荷载下碳纤维/环氧树脂界面的应力-应变曲线和微观结构变化
图6. 恒定荷载下碳纤维/环氧树脂界面的应力-应变曲线和微观结构变化
(3) 阐释了潮湿、盐水、高温环境和荷载作用下纤维/基体界面的性能退化机制(图7)。
图7. 纤维/基体界面在潮湿、盐环境以及高温下的退化机制
本文综述了环境和荷载作用下纤维/基体界面的分子退化模拟研究，包括纤维/基体界面的建模和模拟方法、不同环境和荷载作用下的界面退化情况，有助于从根本上理解FRP复材的性能演化及退化机制，为预测FRP复材长期耐久性能提供理论基础。相关成果以“Degradation
of fiber/matrix interface under various environmental and loading conditions:
Insights from molecular simulations”为题发表于Construction
and Building Materials期刊。原文链接：https://www.sciencedirect.com/science/article/pii/S0950061823008139#s0030
期刊论文：(† Co-First Author, * Corresponding Author, # Group Member)[1] Ruidong
Wu†#, Xing Quan Wang†, Danyang Zhao#, Jia-ao Hou#, Chao Wu*, Denvid Lau*
andLik-ho Tam*, “Degradation
of fiber/matrix interface under various environmental and loading conditions:
Insights from molecular simulations”, Construction and Building
Materials, 2023, 390:131101.[2] Lik-ho Tam†, Marc
A. Ntjam Minkeng†, Denvid Lau, Walid Mansour and
Chao Wu, “Molecular interfacial shearing creep behavior of carbon fiber/epoxy
matrix interface under moisture condition”, Engineering Fracture Mechanics,
2023, 282:109177. [3] Lik-ho Tam†, Ruidong Wu†#, Marc A. Ntjam Minkeng#, Jinqiao Jiang#, Ao Zhou,
Huali Hao, Zechuan Yu and Chao Wu, “Understanding creep behavior of carbon
fiber/epoxy matrix interface via molecular dynamics simulation”, Mechanics of
Advanced Materials and Structures, 2023, 30(19):4052-4064.[4] Lik-ho Tam†, Jinqiao Jiang†, Zechuan Yu, John Orr and Chao Wu,
“Molecular dynamics investigation on the interfacial shear creep between carbon
fiber and epoxy matrix”, Applied Surface Sc-ience, 2021, 537:148013. [5] Chao Wu, Ruidong Wu, Jinqiao Jiang, Lik-ho Tam*, “Recent advances in understanding environmental effects on
deterioration of carbon fiber/epoxy matrix interface in civil engineering
applications via molecular simulation.”, Acta Materiae Compositae Sinica,
2020;37(12):2941-52.[6] Lik-ho Tam, Ao
Zhou, Runxiao Zhang and Chao Wu*, “Effect of hygrothermal environment on
traction-separation behavior of carbon fiber/epoxy
interface”, Construction and Building Materials, 2019, 220:728-738.[7] Lik-ho
Tam,Ao Zhou and Chao Wu*, “Nanomechanical behavior of
carbon fiber/epoxy interface in hygrothermal conditioning: A molecular dynamics
study”, Materials Today Communications, 2019, 19:495-505.[8] Lik-ho Tam, Li
He and Chao Wu*, “Molecular dynamics study on the effect of salt environment on interfacial
structure, stress, and adhesion of carbon fiber/epoxy interface”, Composite
Interfaces, 2019, 26(5):431-47.
[1] Chao Wu, Ruidong Wu# and Lik-ho Tam*,
“Understanding degradation of fiber/matrix interface under environmental
effects using molecular simulation”, in 10th International Conference on FRP Composites
in Civil Engineering (CICE 2021), Lecture Notes in Civil Engineering (Springer,
Cham), 2021, 198:2096-2108.[2] Lik-ho Tam, Jinqiao Jiang# and
Chao Wu, “Understanding Creep Behaviour of Fibre/Matrix Interface via Molecular
Dynamics Investigation”, in Third International Workshop on Seawater Sea-Sand
Concrete (SSC) Structures Reinforced with FRP Composites (3rd FRP-SSC
Workshop), 2020:45.[3] Chao Wu, Jinqiao Jiang# and Lik-ho
Tam*, “An atomistic study of creep behavior in fiber/matrix
interface”, in 22nd International Conference on Composite Materials (ICCM22
2019), Melbourne, VIC: Engineers Australia, 2019: 2526-2535.[4]谭力豪, 吴超,高温盐水环境下碳纤维/环氧树脂界面粘接性能的退化机理研究. 2018年全国固体力学学术会议, 2018, 中国黑龙江哈尔滨.
审核 | 谭力豪
