This paper aims to apply an acoustic emission (AE) method to characterize the damage mechanisms of composite hydrogen pressure vessels (Type IV) with a service pressure of 70 MPa. First, AE signals were captured during the multi-step loading of two vessels.Second, AE feature parameters in time-domain and frequency-domain analyses such as amplitude, frequency, and energy were studied. A multi-parameter statistical analysis (MPSA) method based on empirical mode decomposition (EMD) and K-means algorithm was performed to cluster AE events. Intrinsic mode functions (IMFs) were decomposed by EMD and three IMFs with high frequency were chosen to reconstruct the feature parameters and provide signal pre-processing for K-means clustering analysis. Based on the relationship between AE features and the damage modes, three main clusters with distinguished amplitude, absolute energy, and energy were correlated to matrix cracking, fiber-matrix debonding, and fiber breakage. Besides, the effectiveness of MPSA method for signal classification is validated by principal component analysis (PCA) and fast Fourier transformation (FFT) methods. Finally, the AE parameters of the damages modes, such as amplitude and counts to peak, were studied for both the hydraulic proof test and the burst test. This allows the determination of the changes in the damage mechanisms with increasing pressure. Results show that AE method can be reliably used to characterize the mechanisms of burst damage in composite pressure vessels.

No abstract