Bompadre Francesca, Donnini Jacopo
Department of Materials, Environmental Sciences and Urban Planning (SIMAU), Marche Polytechnic University, 60131 Ancona, Italy.
Materials (Basel). 2022 May 31;15(11):3927. doi: 10.3390/ma15113927.
Nowadays, FRCM systems are increasingly used for the strengthening and retrofitting of existing masonry and reinforced concrete structures. Their effectiveness strongly depends on the bond that develops at the interface between multifilament yarns, which constitute the reinforcing fabric, and the inorganic matrix. It is well known that fabric yarns, especially when constituted by dry carbon fibers, have poor chemical-physical compatibility with inorganic matrices. For this reason, many efforts are being concentrated on trying to improve the interface compatibility by using different surface treatments on multifilament yarns. In this paper, three different surface treatments have been considered. The first two involve yarn pre-impregnation with flexible epoxy resin or nano-silica coating, while the third one involves a fiber oxidation process. Uniaxial tensile tests were carried out on single carbon yarns to evaluate tensile strength, elastic modulus and ultimate strain before and after surface treatments, and also after yarn exposure to accelerated artificial aging conditions (1000 h in saline or alkaline solutions at 40 °C), to evaluate their long-term behavior in aggressive environments. Pull-out tests on single carbon yarns embedded in a cementitious mortar were also carried out, under normal environmental conditions and after artificial exposure. Epoxy proved to be the most effective treatment, by increasing the yarn tensile strength of 34% and the pull-out load of 138%, followed by nano-silica (+9%; +40%). All surface treatments were shown to remain effective even after artificial environmental exposures, with a maximum reduction of yarn tensile strength of about 13%.
如今，纤维增强复合材料（FRCM）系统越来越多地用于现有砖石结构和钢筋混凝土结构的加固与修复。其有效性很大程度上取决于构成增强织物的复丝纱线与无机基体之间界面处形成的粘结力。众所周知，织物纱线，尤其是由干碳纤维构成的纱线，与无机基体的化学物理相容性较差。因此，许多工作都集中在通过对复丝纱线进行不同的表面处理来提高界面相容性上。本文考虑了三种不同的表面处理方法。前两种方法包括用柔性环氧树脂或纳米二氧化硅涂层对纱线进行预浸渍，而第三种方法涉及纤维氧化过程。对单根碳纤维纱线进行了单轴拉伸试验，以评估表面处理前后以及纱线在加速人工老化条件下（在40℃的盐水或碱性溶液中暴露1000小时）的拉伸强度、弹性模量和极限应变，以评估其在侵蚀性环境中的长期性能。还在正常环境条件下和人工暴露后，对嵌入水泥砂浆中的单根碳纤维纱线进行了拉拔试验。结果表明，环氧树脂是最有效的处理方法，可使纱线拉伸强度提高34%，拉拔荷载提高138%，其次是纳米二氧化硅（分别提高9%和40%）。所有表面处理在人工环境暴露后仍显示有效，纱线拉伸强度最大降低约13%。
