Objective  The carbon fiber reinforced plastic (CFRP) propeller has such advantages as light weight, high strength, low vibration, low noise, corrosion resistance and fatigue resistance. In order to accurately ascertain the deformation and strain of CFRP propeller blades under hydrodynamic load, this paper proposes an online measurement method for CFRP propeller dynamic strain under submerged operation conditions.

  Method  Fiber bragg grating (FBG) sensors are embedded in a CFRP propeller, and an underwater dynamic strain test system is built. Two types of test conditions are set: (1) the velocity is 0 m/s, and the rotation speed increases from 50 to 400 r/min; and (2) the rotation speed is 427 r/min, and the velocity increases from 0.0 to 1.6 m/s. The dynamic strain data of the CFRP propeller under the above conditions is obtained by the FBG sensors and analyzed in the time and spectrum domains.

  Results  The results show that, the dynamic strain frequencies of each FBG sensor on the CFRP propeller are the same and related to the rotation speed, while the dynamic strain amplitude of each FBG sensor has no obvious relationship with the rotation speed or velocity, but depends on the position of the sensor, which reflects the structural mechanics features of the propeller.

  Conclusion  The underwater online dynamic strain test of the CFRP propeller is realized, and test results are reasonable and reliable. This provides an important empirical basis for the theoretical design and analysis of the CFRP propeller, which is of great significance for the study of its vibration noise and hydrodynamic performance.