Laser Deposition Joining of Composites for Wind Turbine Blade Repair

风能行业迫切需要具有成本效益的复合叶片修复方法。风力涡轮机叶片受到相当大的磨损和退化，他们的维修往往是必要的。目前，大多数叶片维修使用湿环氧树脂进行。这种修补方法连接强度低，需要较长的加工时间。该奖项支持的研究将为一种新的基于激光的复合材料叶片修复工艺奠定基础。在此过程中，采用激光沉积连接方法，利用微细玻璃粉作为填充材料连接玻璃纤维修补片。激光沉积连接修复纤维增强复合材料也将应用于复合材料结构的修复；例如，那些在国防，航空航天，汽车和压缩气体储存行业。因此，这项研究的结果将有利于美国的经济和社会。研究目标是：(1)建立玻璃粉流温度与操作参数（如激光功率密度和粉末流速）之间的关系；(2)量化玻璃粉流温度对玻璃纤维修补补丁中玻璃粘性流动行为的影响；(3)建立玻璃粉流温度与沉积接头质量（浸润深度、孔隙度、弯曲性能和抗分层性能）之间的关系。为了实现这些目标，将完成三项研究任务。首先，将对同轴粉末流动和激光-粒子相互作用进行数值模拟，以预测玻璃粉末流温度。在各种操作条件下的建模结果将通过粉末流温度的实验测量来验证。其次，进行多物理场建模，以评估粉末流温度对玻璃熔体通过纤维介质随机阵列的粘性流动的影响。通过光学和扫描电镜测量，预测并验证了玻璃填料的浸润深度和冷却沉积接头的孔隙率。最后，通过显微测量渗透深度和孔隙率以及力学测试挠曲性能和抗分层性能，实验确定玻璃粉流温度对接头完整性的影响。

Cost-effective repair methods for composite blades are critically needed for the wind energy industry. Wind turbine blades are subject to considerable wear and degradation, and their repairs are often necessary. Currently, most blade repairs are performed using wet epoxy resins. Such repairs have low joining strength and require long processing time. The research supported under this award will establish the foundation for a novel laser-based process to repair composite blades. During the process, a repair patch of glass fibers is joined employing a laser-deposition joining method utilizing fine glass powders as filler material. Laser-deposition joining repair of fiber-reinforced composites will also have applications where repair of composite structures is needed; for example, those in defense, aerospace, automotive, and compressed gas storage industries. Consequently, the results of this research will benefit the U.S. economy and society. The research objectives are: (1) establishing the relationship between glass powder stream temperature and operational parameters (such as laser power density and powder flow rate), (2) quantifying the effect of the glass powder stream temperature on the glass viscous flow behavior through the repair patch of glass fibers, and (3) establishing the relationship between glass powder stream temperature and deposition joint quality (in terms of infiltration depth, porosity, flexural properties, and delamination resistance). To achieve these objectives, three research tasks will be completed. First, numerical modeling of coaxial powder flow and laser-particle interaction will be performed to predict glass powder stream temperature. The modeling results under various operational conditions will be verified using experimental measurements of powder stream temperature. Second, multi-physics modeling will be performed to evaluate the effect of powder stream temperature on the glass melt viscous flow through the random arrays of fibers media. The infiltration depth of the glass fill and porosity of the cooled deposition joint will be predicted and validated against optical and scanning electron microscopy measurements. Finally, the effect of glass powder stream temperature on the joint integrity will be experimentally determined based on microscopy measurements of infiltration depth and porosity and mechanical testing of flexural properties and delamination resistance.