聚氨酯广泛用于转子叶片复合材料表面作为防砂侵蚀材料。聚氨酯薄膜在使用条件下的失效机理研究对于开发用于转子叶片的最佳聚氨酯薄膜很有用。在这篇文章中,根据聚氨酯薄膜的使用环境确定了砂蚀试验参数。用红外测温仪分析了聚氨酯薄膜在不同冲击角度下的抗砂冲蚀性能和失效机理,傅里叶变换红外光谱仪(FTIR),差示扫描量热计(DSC),场发射扫描电子显微镜(FESEM),和激光共聚焦显微镜(CLSM)。结果表明,与传统的质量损失法相比,体积损失直接测量法能更好地表征聚氨酯薄膜的抗砂冲蚀性能,避免了聚氨酯薄膜中嵌入砂粒的影响。聚氨酯薄膜在低角度冲击下的抗砂蚀能力远低于高角度冲击。在220米/秒的冲击速率下,在30°冲击角下砂蚀15min后的体积损失为57.8mm3,而在90°冲击角下的体积损失仅为2.6mm3。根据实验数据建立了体积损失预测方程。在低角度侵蚀期间,聚氨酯薄膜的损坏主要是由砂切引起的,导致表面材料起皱和堆积,粗糙度的快速增加,和长裂缝的产生。发展中的裂纹的连接会导致聚氨酯膜的大规模脱落。在高角度侵蚀期间,聚氨酯膜的破坏主要是由撞击造成的。冲击引起的小裂缝的连接导致聚氨酯小块脱落,而薄膜粗糙度的变化不像低角度侵蚀时那样显著。在冲击和切削载荷的作用下,软块和硬块的无序排列变得局部有序。然后,腐蚀试验结束后,无序状态恢复。砂粒的侵蚀导致聚氨酯薄膜侵蚀区温度升高,最高温升为6°C,这不会导致聚氨酯薄膜分子结构的显著变化。侵蚀破坏机理是由砂石切割和冲击引起的开裂。
Polyurethane is widely used on the surface of composite materials for rotor blades as sand erosion protection materials. The failure mechanism investigation of polyurethane film under service conditions is useful for developing the optimal polyurethane film for rotor blades. In this article, the sand erosion test parameters were ascertained according to the service environment of the polyurethane film. The sand erosion resistance and failure mechanism of polyurethane film at different impact angles were analyzed by an infrared thermometer, a Fourier transform infrared spectrometer (FTIR), a differential scanning calorimeter (DSC), a field emission scanning electron microscope (FESEM), and a laser confocal microscope (CLSM). The results show that the direct measurement method of volume loss can better characterize the sand erosion resistance of the polyurethane film compared to traditional mass loss methods, which avoids the influence of sand particles embedded in the polyurethane film. The sand erosion resistance of polyurethane film at low-angle impact is much lower than that at high-angle impact. At an impact rate of 220 m/s, the volume loss after sand erosion for 15 min at the impact angle of 30° is 57.8 mm3, while that at the impact angle of 90° is only 2.6 mm3. The volume loss prediction equation was established according to the experimental data. During low-angle erosion, the polyurethane film damage is mainly caused by sand cutting, which leads to wrinkling and accumulation of surface materials, a rapid increase in roughness, and the generation of long cracks. The linking of developing cracks would lead to large-scale shedding of polyurethane film. During high-angle erosion, the polyurethane film damage is mainly caused by impact. The connection of small cracks caused by impact leads to the shedding of small pieces of polyurethane, while the change in the roughness of the film is not as significant as that during low-angle erosion. The disordered arrangement of the soft and hard blocks becomes locally ordered under the action of impact and cutting loads. Then, the disordered state is restored after the erosion test finishes. The erosion of sand particles leads to an increase in the temperature of the erosion zone of the polyurethane film, and the maximum temperature rise is 6 °C, which does not result in a significant change in the molecular structure of the polyurethane film. The erosion failure mechanism is cracking caused by sand cutting and impact.