风电叶片新型拉挤夹芯梁帽弯曲性能试验

Experimental study on flexural performance of novel pultruded sandwich spar caps of wind turbine blades

采用玻璃纤维增强树脂复合材料(GFRP)拉挤条板制造风电叶片夹芯梁帽可以克服传统纤维布铺设工艺中存在的褶皱、气泡等制造缺陷,提升材料模量和强度,减少纤维缝编工序和节约材料成本,是未来风电叶片梁帽发展的趋势之一。以GFRP双轴布为面层、GFRP拉挤条板和方格布为夹芯层的叶片主梁梁帽局部梁段作为研究对象。为研究面层厚度及剪跨比对新型拉挤夹芯梁帽承载能力和破坏模式的影响,开展四点弯曲试验。结果表明:随着面层厚度的增加,拉挤夹芯梁帽的破坏模式从无面层试件的拉挤条板拉裂破坏,发展为单层面层试件的面层拉裂或拉断破坏及多面层试件的下面层剥离破坏。合理设计面层和夹芯的比例,能够控制夹芯结构的破坏模式;拉挤夹芯梁帽的初始刚度随着面层厚度增加及剪跨比减小而增加;面层厚度的增加可以大幅提升结构的承载能力,延缓胶缝的开裂,减小破坏时的承载力损失,并在一定程度上改善结构的脆性行为。

The use of pultruded glass fiber-reinforced polymer(GFRP)strips as sandwich spar caps of wind turbine blades can overcome the manufacturing defects such as wrinkles and bubbles caused by conventional fiber cloth laying process.It can also improve the modulus and strength of the material as well as reduce the manufacturing cost,and hence becomes one of the promising manufacturing techniques for wind blades in the future.To investigate the influence of the face sheet thickness and the shear-span ratio on the strength and failure modes of the sandwich spar cap,a series of sandwich specimens with biaxial GFRP face sheets and pultruded GFRP strips core were tested by four-point bending.The test results show that with the increase of the face sheet,the failure mode of the specimen changes from the rupture of pultruded GFRP strip for the specimen without face sheet,to the damage or rupture of GFRP face sheet for the specimen with single layer face sheet,and to the delamination for the specimen with multilayer face sheets.The failure mode could be controlled by proper design of the ratio between the core and face sheets.Also,the initial stiffness of the sandwich spar cap increases with the increase of the face sheet thickness and with the decrease of the shear-span ratio.Increasing the face sheet thickness could improve both strength and ductility of the test specimens,and could delay the cracking of the glue seam as well as reduce the sudden loss of maximum load.