土木工程应用中碳纤维/环氧树脂界面在环境影响下退化的分子模拟研究进展

吴超; 吴瑞东; 蒋金桥; 谭力豪

doi:10.13801/j.cnki.fhclxb.20200831.003

土木工程应用中碳纤维/环氧树脂界面在环境影响下退化的分子模拟研究进展

doi: 10.13801/j.cnki.fhclxb.20200831.003

1.
北京航空航天大学　交通科学与工程学院，北京 100191
2.
北京航空航天大学　数学科学学院，北京 100191

基金项目: 国家自然科学基金 (51808020；51978025；51911530208)；中国博士后科学基金 (2017M620015；2018T110029)；中组部第十二批“千人计划”青年项目

详细信息

通讯作者:
谭力豪，博士，助理教授，研究方向为复合材料、竹材/木材等土木工程材料的多尺度动力学模拟　Email：leo_tam@buaa.edu.cn

中图分类号: TB332；TU599
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出版历程
- 收稿日期: 2020-06-18
- 录用日期: 2020-08-20
- 网络出版日期: 2020-09-01
- 刊出日期: 2020-12-15

Recent advances in understanding environmental effects on degradation of carbon fiber/epoxy matrix interface in civil engineering applications via molecular simulation

1.
School of Transportation Science and Engineering, Beihang University, Beijing 100191, China
2.
School of Mathematical Sciences, Beihang University, Beijing 100191, China

摘要

摘要: 在土木工程领域，碳纤维增强复合材料 (CFRP) 由于有着优异的力学性能而被越来越多地用在建筑结构中。碳纤维与环氧树脂之间粘结界面的性能对于 CFRP 内部应力的有效传递极为关键，并很大程度上决定了复合材料的长期耐久性能。然而，纤维/树脂粘结界面易受到湿热、盐雾及海水等恶劣环境的侵蚀，导致界面脱粘及最终的复材破坏。为了确保复材的长期耐久性能，需要全面认识界面在环境侵蚀下的退化行为。分子动力学模拟可以“自底向上”地描述界面在环境侵蚀下的行为，有利于探究界面的退化和失效机制。本文综述了不同环境因素影响下碳纤维/环氧树脂界面退化的分子模拟研究进展，包括界面模型的建立，界面在潮湿、盐雾等环境中结构、性能的退化及其背后的机制。最后，提出了未来界面退化的研究方向，例如纤维/树脂粘结界面模型的进一步完善。
- 碳纤维增强复合材料 /
- 纤维/树脂粘结界面 /
- 耐久性能 /
- 环境影响 /
- 分子模拟
Abstract: In civil engineering, carbon fiber-reinforced polymer (CFRP) composite has been increasingly used in building structures, due to its excellent mechanical properties. The interface between carbon fiber and epoxy matrix is critical for the stress transfer in the CFRP, which largely determines the long-term durability of composite material. However, the fiber/matrix interface is vulnerable to the hygrothermal and salt environment, which leads to the interfacial debonding and final composite failure. In consideration of the durability issue of composite material, the interfacial degradation between fiber and matrix under environmental effects should be fully understood. Molecular dynamics simulation can provide a bottom-up description of the fiber/matrix interface in the simulated environments, which contributes to the understanding of the interfacial degradation mechanism. In this work, the recent simulation progress in understanding the environmental effects on the degradation of carbon fiber/epoxy matrix interface from a nanoscale perspective was reviewed, including the development of the interface model, the degradation of the interfacial structure and properties in various environments such as wet and salt environment, and the underlying degradation mechanism. Meanwhile, future research direction involving further development of the fiber/matrix interface model was also provided.
- carbon fiber-reinforced polymer composite /
- fiber/matrix interface /
- durability /
- environmental effect /
- molecular simulations

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图 1 碳纤维增强复合材料(CFRP) 的多尺度结构示意图

Figure 1. Hierarchical structure of carbon fiber reinforced polymer (CFRP) at different length scales ((a) Macroscale CFRP; (b) Microscale interface region exists between carbon fiber and epoxy matrix, where water can seep intothe local interface, leading to the interfacial debonding; (c) Molecular interface model in wet environment)

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图 2 不同环境中的碳纤维/环氧树脂粘结界面模型

Figure 2. Model development of carbon fiber/epoxy matrix interface in various environments ((a) Epoxy molecule is set on top of the substrate representing carbon fiber outer-layer to form the interface model; (b) Interface model is immersed in the water box to simulate the wet environment; (c) Salt ions are added in the water box to simulate the salt solution)

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图 3 碳纤维/环氧树脂粘结界面的结构与性能

Figure 3. Structure and properties of the carbon fiber/epoxy matrix interface

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图 4 环境因素影响下的界面退化机制示意图

Figure 4. Interface degradation in wet environment((a) No obvious hair-like bridge exists to bond the fiber and matrix in wet environment, which cannot impede the interfacial debonding process;(b) Local aggregated water molecules form H-bonds with epoxy functional groups at the interface)

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图 5 不同环境中树脂内部和树脂-溶液氢键数目对比

Figure 5. Comparison of number of H-bonds within epoxy and between epoxy and solution in different environments

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表 1 经验性力场的适用范围

Table 1. Applicability of empirical force fields

Empirical force field	Material	Property
CVFF	Small organic crystals, gas phase structures, and organic, polymeric, and biological materials	Structures, binding energies, vibrational frequency, conformational energies, and mechanical properties
Dreiding	Biological, organic, and some inorganic molecules	Bulk material properties, including geometries, conformational energies, intermolecular binding energies, and crystal packing
PCFF	Organic and inorganic materials, and polymers	Cohesive energies, mechanical properties, compressibilities, and heat capacities
COMPASS	Organic and inorganic molecules, polymers, and metal materials	Molecular structure, conformation, vibration and thermodynamic properties of isolated and condensed molecules
Notes: CVFF—Consistent valence force field; PCFF—Polymer consistent force field; COMPASS—Condensed-phase optimized molecular potentials for atomistic simulation studies.

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表 2 不同环境影响下碳纤维/环氧树脂粘结界面结构与力学性能的退化：分子模拟研究结果^[24-25]

Table 2. Structure and mechanical properties degradation of carbon fiber/epoxy matrix interface under various environmental effects: Molecular simulation results^[24-25]

Environment	Peak density of epoxy/(atom·nm⁻³)		Glass transition temperature of epoxy/℃
Environment	27℃	50℃	Glass transition temperature of epoxy/℃
Dry	21.2	21.5	185.5
Wet	17.0 (−20%)	16.8 (−22%)	109.3 (−41%)
Salt	15.9 (−25%)	15.8 (−27%)	99.5 (−46%)

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表 3 不同环境影响下碳纤维/环氧树脂粘结界面粘结性能的退化：分子模拟研究结果

Table 3. Adhesion degradation of carbon fiber/epoxy matrix interface under various environmental effects: Molecular simulation results

Environment	Simulation technique	Simulation result	Reference
Wet	Water molecules are added to the interface region	Interfacial shear stress decreases by 38% compared with the dry case	[40]
Wet	Interface is immersed in a large number of water molecules	Interfacial adhesion energy decreases by 58% and 69% respectively compared with the dry case	[20-21]
Salt	Interface is immersed in a large number of water molecules and 5 wt% of Na⁺ and Cl⁻ ions	Interfacial adhesion energy decreases by 75% compared with the dry case	[23]
Hygrothermal	Interface is conditioned in 50℃ dry, wet, and salt environments	Interfacial adhesion energy in 50℃ dry, wet, and salt environments decreases by 13%~14% compared with the 27℃ cases; interfacial adhesion energy in 50℃ wet and salt environments decreases by 73% and 78% respectively compared with the 27℃ dry case	[24]

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