Technical Investigation On Preparing Aluminium Matrices Smart Composites By Ultrasonic Welding

Metal matrix smart composite materials with self-awareness, self-diagnosis and self-management ability, compared to polymer-matrix smart composite materials with higher strength, suitable for high temperature, corrosive and harsh environments, to meet higher security conditions, etc. This paper uses the rapid prototyping method of ultrasonic metal welding embedded optical fiber gratings (fiber Bragg gratings, FBG) to 6061 aluminum alloy matrices to make metal-matrix smart composite materials/structure. The 6061 aluminium alloy ultrasonic welding and fiber optic sensors embedded in Al matrix are studied in a theoretical analysis and finite element simulation. The performance research of organization and sensing after the FBG sensors embedded in Al matrix are conducted by experiments.Firstly, two key mechanisms were identified which lead to embedding of FBG sensors within a metal matrix, known as the surface effect and volume effect. The surface effect describes the interfacial friction between the two mating surfaces effect, while the volume effect concerns the internal stresses and plastic deformation within the metal, during ultrasonic metal welding. Based on these two key mechanisms for establishing the material model and friction model, and relying on the computational analysis model achieve the thermal-mechanical coupled finite element analysis of the ultrasonic metal welding. The results show that the aluminum with the highest temperature and the maximum plastic deformation at the aluminum foil/sonotrode interface, and the maximum temperature below the aluminium alloy melting temperature. In the case of the welding pressure 175MPa, ultrasonic amplitude 8.4μm, welding time 60ms reach the maximum temperature of 357.466℃. With welding pressure increasing, the experiment result shows that the Al matrix stick in sonotrode. Based on the previous results successfully perform thermo-mechanical finite element analyses of the fiber embedding within aluminum alloy 6061 matrices, show that the FBG sensors can be embedded in Al matrix and not to be broken to invalid. In addition, through the experiments, obtain the optimized welding parameters of the FBG sensor within Al matrix. The parameters:ultrasonic amplitude 35μm, welding time 230ms, welding air pressure 0.5MPa, sonotrode surface 15×15mm square sand grinding surface. Further deepened the understanding of ultrasonic metal welding:After ultrasonic metal welding, the hardness of the matrix material has been increased, especially proximity the fiber. With the welding time and ultrasonic energy increases, the connection strength tend to increase linearly firstly then basically unchanged. The grain size of the matrix material is almost unchanged, however the grain orientation is changed, so that organizations isotropic enhanced.FBG sensors embedded in metal matrices are easily damaged and broken. A method is therefore presented for the metallization of FBG by the combination of electroless nickel plating and electro nickel plating, followed by embedding the coated FBG in an aluminum alloy 6061 matrix successfully by using optimization welding parameters. The smart metal structures that were fabricated had good temperature sensing properties. The fabrication of smart metal structures using ultrasonic welding was shown to be feasible.