Ultrasonic Welding Of Short Carbon Fiber Reinforced Nylon66 Composite

Modern automobile industry needs to produce safer and more reliable products to meet the needs of the government and consumers. In order to improve the fuel economy and reduce emissions, lightweight body is a good solution. More and more lightweight materials such as aluminum alloy, magnesium alloy, especially the nylon and nylon composite material are used in the body of cars to reduce vehicle weight. Carbon fiber reinforced nylon composite material is a new type of high-performance materials, which have excellent mechanical properties, such as high strength, low density, and widely used in the automotive industry, aerospace and other emerging areas. To obtain quality connection of carbon fiber reinforced nylon composites in automobile production, efficient and reliable connection methods are necessary. Ultrasonic weld has many advantages: joining large complex thermoplastic parts, relatively short cycle times, high efficiency, simple equipment, easy to operate, and is widely used in automobile industry, electronics and other fields. Therefore, it may be a good joining method of carbon fiber reinforced nylon composites.In this study, the effects of welding parameters such as time, pressure on the welding strength were firstly studied. It is found that the best welding strength can be obtained using the parameters of a weld pressure of 0.15 MPa and a welding time of 2.1s. Secondly, the microstructure of joints was investigated.. The microstructure of the welded joints could be d ivided into basic zone, heat affected zone and the fusion zone. The thicker fusion zone can increase the joints strength. But when the welding energy are too much, the surface of the joints will be collapsed and the porous zone will be thickened. Both them caused a decrease in joints strength. In order to develop a suitable control method of the welding quality, the relation of the joint strength of the ultrasonic welded carbon fiber reinforced nylon 66 composites and welding area is investigated. The process window used to evaluate the welding quality was developed. Using the welding parameters in the welding parameters, the minimal welding area of 380mm2 can be ensured the joint strength carbon fiber reinforced nylon 66 composites is above 5.2k N.Adding short carbon fibers(C f)to nylon66 could improve the tensile strength, tensile modulus and other performance of carbon fiber reinforced nylon 66 composites. The analysis of the DMA found that the storage modulus and loss modulus increased with the increase of C f content. The high energy storage modulus could make more energy be transmitted into the welding zone while high loss modulus make more vibrational energy is dissipated at welding zone by hysteresis losses in the weld process. The welding interface of C f/nylon 66 composites with 30 mass% could absorb more energy, which caused a thicker fusion zone and larger C f content in fusion zone. Therefore, The C f/nylon 66 composites with 30 mass% have a high joint strength. The ultrasonic welding joints of C f/nylo n 66 composites with 20-30 mass% C f were mainly interface failed, most of C f/nylon 66 composites with 40 mass% C f were failed in the workpieces breaking while nylon 66 mainly failed by the mixed failure mode. The most suitable C f content of the composites for ultrasonic welding is 30 mass%.