The temperature sensitivity of fiber bragg gratings embedded in an Al 6061 matrix by ultrasonic welding

The low temperatures and low pressure employed in ultrasonic welding make it suitable for embedding optical fiber gratings (fiber Bragg gratings (FBGs)) in the fabrication of 3D smart composites. However, 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 in order to fabricate smart metal structures. Experimental results show that nickel plating can protect the FBG and provide benefits in the fabrication of aluminum alloy smart structures using ultrasonic welding. The temperature-sensing properties of smart metal structures fabricated in this way are analyzed, and the results show that the temperature sensitivity has been improved twofold. Also, the temperature sensing shows good linearity, and the temperature cross-sensitivity has been effectively controlled; the temperature resolution has also been improved, making the measurements more accurate.