Mechanical Evaluation of High-Strength and High-Modulus Fibers and Influence of Environment of Fracture Behavior

高强度和高弹性模量纤维在其他技术领域的需求越来越大。研究了单纤维的断裂行为，包括水、真空、电子辐射和紫外线辐射的环境影响。采用高分辨率扫描电镜和原子力显微镜对纤维损伤进行了仔细观察。所研究的纤维是陶瓷前驱体纤维，包括氧化铝（住友公司的Altex）、碳化硅（日本炭素公司的Nicalon）和硅- c - ti - o（宇部公司的Tyranno），有机纤维，杜邦公司的Kevlar和帝人公司的Technora芳纶纤维。单陶瓷纤维强度随环境含水量的增加和驱替速率的减小而降低。单纤维表面的AFM纳米评价表明，水分子诱导裂纹缓慢扩展，导致纤维强度下降。芳纶纤维的纵向拉伸强度、纵向和横向弹性模量受吸水率和紫外线辐射的影响而降低。然而，电子辐射对材料力学性能的影响较小。纵向拉伸强度在真空环境下也有所下降，且由真空环境转为空气环境促进了纵向拉伸强度的下降。利用原子力显微镜（AFM）对芳纶纤维进行纳米级评价表明，吸水、紫外线辐射和真空环境促进了纤维表面的“结节”和“坑”等损伤，促进了纤维的分裂，从而影响了芳纶纤维的力学性能。

High-strength and high-elastic modulus fibers are gaining increasing demand for further technological areas. This investigation demonstrates the fracture behavior of single fiber including environmental influences of water, vacuum, electron radiation, and ultra-violet radiation. Fiber damage was closely examined by using high-resolution scanning electron microscope and atomic force microscope. The fibers investigated were ceramic precursor fiber including alumina (Altex by Sumitomo) , SiC (Nicalon by Nippon Carbon) and Si-C-Ti-O (Tyranno by Ube) , and organic fibers, aramid fibers of Kevlar by Du Pont and Technora by Teijin.The single ceramic fiber strength decreased with increasing water content in an environment and with decreasing displacement rate. Nanoscopic evaluation of single fiber surface by AFM showed that water molecule induced slow crack growth, resulting in a decrease in fiber strength. As for aramid fibers, the longitudinal tensile strength and longitudinal and transverse elastic modulus decreased by water absorption and ultraviolet radiation. However, a decrease of mechanical properties by electron radiation was small. The longitudinal tensile strength also decreased in vacuum, and its decrease was promoted by changing an environment from vacuum to air. Nanoscopic evaluation by using AFM showed that surface damage including "nodule" and "graves" was promoted by water absorption, ultraviolet radiation and vacuum environment, and it promoted fiber splitting, resulting in mechanical properties of aramid fibers.