纤维增强复合材料结构耐久性定量设计的理论问题

The research and application of fiber reinforced plastic(FRP) materials in civil engineering has been greatly developed, and the industrial chain of the strengthening technology with it has already been formed， and the technology of new structure is in the continuous improvement. Considering the durability design requirements of structure with FRP under complex environmental conditions, it is of great theoretical significance and engineering value to establish a quantitative design method. Existing research usually take the strength degradation as an evaluating indicator for degradation of durability of FRP， which has strong uncertainty and discreteness. This project intends to carry out the research of the variation of design parameters based on the variation of the Young's modulus of FRP. A series of samples with different ratio and type of fibre were prepared， then test the Young's modulus of the same sample under different cycle time. Three typical environmental factors are considered, and then analyze and build the evaluation model of FRP materials under various typical environments based on the change of Young's modulus, thus determine the evaluation and design indexes and models of the durability of FRP. This project analyze the deterioration mechanism of FRP with multi factor coupling and establish the coupling model of the performance degradation of FRP based on the modern mathematical method. At the same time, analyze the occurrence mode, development rules and typical failure modes of FRP of its corrosion damage under different environmental factors， and definite the damage limit state of different kinds of FRP. The project aims to build an design model for durability of FRP based on test and mathematical methods，and provide a theoretical basis for quantitative design of durability of FRP in civil engineering.

基于复材结构在复杂环境条件下的耐久性设计需求，建立定量设计方法具有十分重要的理论意义和工程价值。既有研究中，复合材料的耐久性退化规律表述都以强度退化为基准，鉴于这种表述是建立在破坏性测试、数据来源非同体、复合材料的复杂多样性的基础上形成的，具有较强的不确定性和离散性。本项目拟开展针对复合材料弹性模量变化为基准的设计参数变化规律研究。通过三种典型环境因素下的复材试样长期性能比对试验，分析复材弹性模量退化机理，建立各种典型环境下复材弹性模量变化规律模型，及基于现代数学方法的多因素耦合模型。分析不同环境因素下复材腐蚀损伤的发生模式、发展规律、典型的破坏形态，研究不同类型复材的破坏特征及规律，给出其破坏极限状态的分类定义。为土木工程中复材结构的耐久性定量设计方法的建立提供理论基础。

复合材料具有很好的可设计性，但是在应用过程中其性能受环境的影响很大。与航空航天等领域不同，对于土木工程，尤其是海洋工程，复杂的工程环境下复材结构耐久性定量设计方法的缺乏直接阻碍了复材的应用。所以研究复材在复杂环境条件下的性能退化机理，建立适合于土木工程的复材及其结构的耐久性概念、合理的耐久性定量设计方法是极为必要和迫切的前沿工作。.研究工作包括：.1）发明了复材性能的同体测试方法、侵蚀深度测试方法、侵蚀速率测试方法。基于五种典型环境、三种复合材料，制备了436个拉伸试件、6组侵蚀深度测试非标试块，已完成了700余次测试。结果表明：同体测试方法与传统的强度测试方法的测试结果具有一致性，且精度更高。侵蚀深度与侵蚀速率测试方法可以较准确测量复材中侵蚀边界，确定侵蚀的极限状态。.2）定义了复材结构的三种极限状态。当复材仅作为耐久性构件时。环境作用下侵蚀深度达到结构控制厚度时，为耐久性极限状态。复材仅作为承载构件时。与传统结构的承载力极限状态一致。复材同时作为承载和耐久构件时。当承载力和耐久性其中一种或者都达到上述规定的极限状态时为结构的极限状态。.3）提出了复材结构耐久性定量设计的框架。基于前述的定义，将各种环境作用因素的效应耦合，最终以“环境作用能”的概念定义为作用效应。考虑复合材料为铺层结构的特点，建立点侵蚀模型和层侵蚀模型，将复材结构定义为具有充能效应的离散单元体集合，单元能够容纳的环境作用能上限即为单元抗力。抗力与环境、复合材料性质、材料应力状态、材料侵蚀程度等有关。对于侵蚀的过程定义为单元的充能过程，当任一单元所能容纳的作用能达到上限时达到平衡状态。这样可以定量进行既有复材结构的剩余耐久性寿命预测或者进行新建复材结构的耐久性设计。.发表论文8篇，申请发明专利6项，获得实用新型专利授权2项，成果可以分类应用于科研和工程设计中。.

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