Experimental Studies on Micro-fracture Mechanics of High-Temperature Polymer Matrix Composites

实验研究了高温聚合物基复合材料层合板在准静态、单调和重复疲劳载荷作用下的微断裂过程和机理。采用三种不同类型的显微镜和位移速率控制加载装置，对损伤的发生和生长进行了原位显微镜观察。选择交叉层合板作为高性能碳纤维增强高温环氧复合材料的基本层合结构。损伤演化过程包括三个阶段：(1)横向层内横向裂纹萌生；(2)多个横向裂纹形成；(3)横向裂纹尖端分层萌生和扩展。在上述定量实验结果的基础上，提出了一些新的理论模型来预测损伤演变。所测试的CFRP材料包括：(1)传统的180次硫化胶固化TGDDM/DDS体系（T300/3601），(2)改进的增韧体系（T800H/3631），(3)层间树脂膜层的层间增韧体系（T800H/3631- fm300），以及(4)尼龙颗粒分散层间增韧体系（T800H/3900-2）。层压板构型为[0/90_n/0](n=4,8,12).2。通过光学显微镜（OM）、扫描电子显微镜（SEM）和扫描声学显微镜（SAM）在每个加载阶段成功地进行了现场显微镜观察。在20和80℃的温度条件下，观察了(1)横向裂纹萌生、(2)多个横向裂纹形成、(3)横向裂纹尖端分层萌生和扩展等微观变形破坏过程，研究了温度效应。基于90层的统计强度分布，提出了一种新的横向裂纹发展演化规律。基于能量平衡的概念，提出了横向裂纹尖端分层的新演化规律。这两种理论预测都被证明是充分有效的，可以解释定量实验结果。横向裂纹和分层之间的相互作用也被考虑为更好的预测。这些理论也适用于疲劳载荷试样。少

The pupose of the present investigation is to study experimentally the micro-fracture process and mechanism of high-temperarture polymer matrix composite laminates under quasi-static monotonic and repeated fatigue loadings. Three diffirent types of microscopes with displacement-rate-controlled loading devices were used for in-situ microscopic observations of damage initiation and growth. Cross-ply laminates were chosen as basic laminate configurations for high-performance carbon fiber reinforced high-temperature epoxy composites. The damage evolution includes the following three stages : (1)Transverse crack initiation in transverse layrs, (2)Multiple transverse crack formation, and (3)Initiation and growth of delamination from tips of transverse cracks. Based on the above quantitative experimental results, some new theoretical models were proposed to predict the damage evolution.1. The tested CFRP materials include (1)a conventional 180ﾟC-cured TGDDM/DDS system (T300/3601), (2)an impro … More ved toughened system(T800H/3631), (3)an interlaminar-toughened system with interlaminar resin film layrs(T800H/3631-FM300), and(4)a new interlaminar-toughened system with nylon-particle-dispersed interlaminar layrs(T800H/3900-2). The laminate configurations were[0/90_n/0](n=4,8,12).2. In-situ microscopic observations were successfully conducted by a combination of an optical microscope(OM), a scanning electron microscope (SEM), and a scanning acoustic microscope (SAM) with each loading stage. The microscopic deformation and failure processes such as, (1)transverse crack initiation in transverse layrs, (2)multiple transverse crack formation, and(3)initiation and growth of delamination from tips of transverse cracks, were observed at 20ﾟC and 80ﾟC to study the temperatue effects.3. A new evolution law for transverse crack development was proposed based on the statistical strength distribution of 90ﾟlayrs. A new evolution law for delamination from tips of transverse cracks was also proposed based on the energy balance concept. Both theoretical preditions were found to be sufficiently valid to explain the quantitative experimental results. An interaction between transverse cracks and delaminations was also considered for better prediction. These theories were also extended for fatigue-loaded specimens. Less