Wölfel Enrico, Brünig Harald, Curosu Iurie, Mechtcherine Viktor, Scheffler Christina
Leibniz-Institut für Polymerforschung Dresden e. V. (IPF), Hohe Straße 6, 01069 Dresden, Germany.
TU Dresden, Institute of Construction Materials, 01062 Dresden, Germany.
Materials (Basel). 2021 Feb 4;14(4):722. doi: 10.3390/ma14040722.
In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber-matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young's moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber-matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.
在应变硬化水泥基复合材料（SHCC）中，聚丙烯（PP）纤维常用于通过微裂纹桥接来提供延展性，特别是在承受高加载速率时。为了对SHCC进行有目的的材料设计，需要进行基础研究，以了解取决于纤维力学性能和纤维 - 基体相互作用的失效机制。因此，使用熔体纺丝设备生产了直径在10至30μm之间、具有不同拉伸强度水平和杨氏模量、且有圆形和三叶形横截面的PP纤维。在单纤维拉伸实验和纤维材料的差示扫描量热法（DSC）中评估了纺丝过程中拉伸参数引起的结构变化以及上浆表面改性。应用扫描电子显微镜（SEM）、原子力显微镜（AFM）和接触角测量来确定纤维表面的形貌和润湿性。在单纤维拔出实验（SFPO）中研究了准静态和动态加载下的纤维 - 基体相互作用。微观表征的主要发现表明，纤维拉伸强度的提高与高表面粗糙度引起的机械联锁增强相结合，导致动态加载下能量吸收的改善。从圆形纤维横截面变为三叶形纤维横截面时，可以观察到进一步的增强。
