PVA短纤维和粉煤灰对地聚合物基复合材料流变学行为和弯曲性能的影响

利用自行研制的活塞式挤压流变仪研究了掺加聚乙烯醇(PVA)短纤维和粉煤灰的地聚合物浆体在挤压过程中的流变学特性，在此基础上通过单轴挤压机成功制备出宽厚比=12.5∶1.0的短纤维增强地聚合物基复合材料。利用MTS电液侍服机系统研究了各种纤维和粉煤灰掺量的地聚合物基复合材料的弯曲行为。采用扫描电镜(SEM)研究了地聚合物基复合材料中纤维的分布、取向、纤维-基体间界面，以及弯曲实验后试样断裂面上的纤维伸出长度、纤维尖端断裂形貌和纤维表面组织，从细观和微观角度探讨各种地聚合物基复合材料微观结构和弯曲破坏机制。结果表明：PVA短纤维的加入改变了地聚合物浆体的破坏模式，由脆性破坏变为延性破坏；对于不掺或掺加少量粉煤灰(≤10%)的地聚合物基复合材料弯曲强度高，但延性小，当粉煤灰的掺加量≥30%时，地聚合物基复合材料的弯曲强度显著下降，但延性增大。

Effect of PVA short fiber and fly ash on rheological and flexural behaviors of geopolymer composites

Rheological behaviors of geopolymeric pastes incorporated with polyvinyl alcohol (PVA) short fiber and fly ash were investigated by using the specially designed ram rheometer. Based on the rheological testing results，the  PVA short fiber reinforced fly ash-geopolymer composite (SFRGC) (width to height ratio=12.5∶1.0) manufactured by single-screw extrusion technique was successfully prepared with different  the fiber volume fractions and fly ash contents. The flexural behaviors were studied on the SFRGC by using materials testing machine. The corresponding microstructure and the failure mechanism were also explored by SEM. The results show that PVA fiber addition greatly increases the ductility of SFRGC，especially in the case of high volume fraction of fibers，resulting in a change of the impact failure mode from brittle pattern to ductile one. Comparatively fly ash addition also exhibites obvious influence on the flexural properties. SFRGC without or with low percentage of fly ash (≤10%) has high flexural strength，but low ductility. SFRGC with high percentage of fly ash (≥30%) has a low flexural strength，but a large defection.