碳/亚麻纤维混杂复合材料层间断裂韧度

Interlaminar fracture toughness of carbon/flax fiber hybrid composite

为提升碳纤维增强复合材料的抗分层能力,将亚麻纤维引入碳纤维增强复合材料,制备碳/亚麻纤维混杂复合材料。采用双悬臂梁实验和端部缺口梁弯曲实验研究碳/亚麻纤维混杂复合材料的层间断裂韧度,并与碳纤维增强复合材料进行对比,用扫描电子显微镜观察材料断裂表面微观形貌。结果表明:碳/亚麻纤维混杂复合材料的Ⅰ型和Ⅱ型层间断裂韧度与碳纤维增强复合材料相比分别提高了250%和23.86%;碳纤维增强复合材料断裂面上碳纤维表面较为光滑,说明其与树脂结合能力较差,导致较低的层间断裂韧度,而碳/亚麻纤维混杂复合材料的层间断裂面发现亚麻纤维单根纤维断裂、剥离、缠结,亚麻微纤丝剥离、缠结及亚麻微纤丝与碳纤维缠结等多尺度模式破坏。由多尺度结构亚麻纤维带来的多尺度模式破坏在裂纹扩展过程中消耗较多能量,即为碳/亚麻纤维混杂复合材料层间断裂韧度的提高机理。

The application of carbon fiber reinforced composites(CFRP) was limited by their poor delamination resistance.However, the hierarchical microstructure of flax fibers could help to improve the interlaminar properties of the composite. Therefore,the interlaminar fracture toughness of CFRP composites can be improved by hybridized flax with carbon fibers. In this study, the carbon/flax fiber hybrid composites(CFFRP) were manufactured by moulding process. The mode Ⅰand mode Ⅱ interlaminar fracture toughnesses of CFFRP composites were studied by double cantilever beam(DCB) and end-notched flexure(ENF) tests, and were compared with those of CFRP composites. The results show that the Mode Ⅰinterlaminar fracture toughness of CFFRP composite is 1.29 kJ/m;, which is about 3.5 times higher than that of CFRP composites(0.37 kJ/m;). The Mode Ⅱinterlaminar fracture toughness is 1.09 kJ/m;and is about 23.86% higher than that of CFRP composites(0.88 kJ/m;). The interlaminar fractured surfaces of CFRP and CFFRP composites are observed with the aid of scanning electron microscopy(SEM). From the microscopies of the fractured CFRP specimens it can be seen that pure delamination by the peeling of carbon fibers from epoxy resin is obtained for CFRP composites. The surfaces of carbon fibers were relatively clean and few epoxy resin fragments attached. The weak interfacial properties between carbon fiber and epoxy resin cause a lower GⅠc for CFRP composites. On the contrary, from the observation of SEM photographs of flax fiber layers in the interlaminar fractured CFFRP composites, fiber breakage, fiber peeling and fiber entanglement are founded. On the fractured carbon fiber layer, there are some flax fibers tangling with carbon fibers. These multi-scale failure modes due to the unique microstructure of the flax fibers may make the crack propagation become difficult and thus lead to the GⅠc and GⅡc increased for CFFRP composites than those of CFRP composites.