基于自动铺放技术的热塑性复合材料原位固化成型研究进展:热传导行为及层间性能

Light weight, high strength and designable performance make fiber-reinforced composites far superior to metallic materials in weight reduction, fatigue resistance, corrosion resistance, maintainability, and increasingly prevalent in aerospace, transportation, national defense and other fields. Thermoplastic composites have a great deal of advantages such as high toughness, high impact, unlimited storage cycle and recyclability. The robotic placement technology is especially suitable for forming large-size and complicated composite components by virtue of high forming efficiency and high automation. On the other hand, the rapid development of in-situ consolidation technology for thermoplastic composites has led to increased production efficiency, reduced production cost, and significantly improved product quality. Hence the robotic prepreg placement and in-situ consolidation has the potential to become an advanced and promising technique for manufacturing main load-bearing parts of large aircraft in the future. However, as a high-temperature manufacturing process, the placement-consolidation of thermoplastic composite involves some related problems such as thermodynamic coupling. The adoption of heat source is a crucial point for in-situ consolidation, which directly affects the quality and placement efficiency. The heat input to the system can cause molecular chain flow, and the attendant macroscopic change, during the placement-consolidation process, manifests as the transformation of thermoplastic polymer from solid state to molten state and then again to solid state. The whole process is short-duration but quite complicated and associated with a series of physical changes, and has become one of the global hotspots in the field of high-performance thermoplastic composites. The commonly used heating sources in the placement-consolidation of thermoplastic composites mainly include hot air, laser, ultrasonic wave, electron beam, etc. Among them, hot air heating has long been studied with a well-established theoretical interlaminar heat transfer model, and considerable and fruitful efforts have been made focusing on the temperature field of the mat layer. At present, the majority of foreign researchers are dedicated to laser heating, and sufficient results have proved that laser has a significant superiority in product's interlaminar properties against hot air as auxiliary heat source. In addition, researchers have proposed various theoretical models for the prediction of the final fusion strength, but actually the placement-consolidation derived components have inferior mechanical properties to the autoclave cured ones according to the measurements, demonstrating the necessity for further theoretical and practical exploration. The present review is mainly concerned with the technology of robotic prepreg placement and in-situ consolidation with respect of thermoplastic composites manufacturing. It renders a detailed introduction and discussion, from the perspectives of heat transfer behavior and product's interlaminar properties, over the research progress in various aspects of this emerging technology, such as the placement process, the heat transfer model, the heat source for in-situ consolidation, the degree of intimate contact, the degree of healing and the interlaminar bonding, etc.