Based on the different failure modes of FRP composites under random vibration fatigue loading, FRP composites are categorized into brittle and ductile types. The study summarizes the damage evolution patterns of these two types of FRP composites under random vibration fatigue loading, with matrix cracking and delamination being the primary damage modes. A new model is proposed to describe the degradation of natural frequency in FRP composites under random vibration fatigue loading, quantitatively accounting for the effects of different damage modes on natural frequency reduction. The applicability of the model is validated using random vibration fatigue test data from two materials of different characteristics: 2D woven ceramic matrix C/SiC composites and 2D woven glass fiber resin-based composites. The results indicate that this model accurately describes the natural frequency degradation behavior of FRP composites under random vibration fatigue loading.

In order to overcome the low precision of vibration fatigue life analysis of complex engineering structures, a structural dynamic model updating method for random vibration fatigue life prediction was established. In this model updating method, the stiffness and modal damping of key parts such as structural connection are extracted as model modification parameters. The approximate model of modified parameters and target is established to replace the finite element model of complex structure based on the Kriging method. The actual natural frequency and random vibration response spectrum of the structure are taken as the modified objectives to design the optimization experiment and find the optimal model parameters. And based on the amplitude probability density method of random vibration fatigue life analysis, the vibration fatigue life of complex structure is obtained. Finally, the method is verified by structural dynamic experiment. The result shows that the method can effectively modify the parameters of dynamic finite element model for the prediction of structural vibration fatigue life, and improve the accuracy of structural random vibration fatigue life prediction.