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

高强高弹纤维对未来技术领域的需求越来越大。这项研究展示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。用高分辨率扫描电子显微镜和原子力显微镜对纤维损伤进行了仔细观察。所研究的纤维包括氧化铝(住友的Altex)、碳化硅(Nippon Carbon的Nicalon)和Si-C-Ti-O(Ube的Tyranno)等陶瓷原丝纤维，以及有机纤维、杜邦的芳纶纤维和泰金的Technora纤维。用原子力显微镜对单纤维表面进行纳米评价，结果表明，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均因吸水和紫外线照射而降低。然而，电子辐射对力学性能的影响很小。纵向抗拉强度在真空中也有所下降，改变真空到空气的环境可以促进纵向抗拉强度的下降。AFM纳米分析表明，吸水、紫外线和真空环境促进了芳纶纤维的表面损伤，包括“结节”和“坟墓”，并促进了纤维的裂解，从而提高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.