Damage Evolution and Failure Mechanism of Composite Laminates Under Low‐Velocity Impact: Insights From Acoustic Emission and Finite Element Modeling

ABSTRACT To quantify the damage evolution and reveal the failure mechanism of composite laminates during the low‐velocity impact (LVI), a synergistic approach of acoustic emission (AE) technology, and finite element (FE) simulation was proposed. It is the short duration of LVI and the coexistence of multiple damage mechanisms that make the detected AE signals highly complex. The variational mode decomposition (VMD) method was used to effectively separate the AE signals induced by material damage from the vibration waveforms caused by impact. The obtained Intrinsic Mode Functions (IMFs) were subjected to the Hilbert‐Huang Transform (HHT) to identify the frequency ranges corresponding to the three damage mechanisms. Based on the cumulative energy analysis of IMFs, the laminates exhibit the most severe delamination damage under the 20 J impact. In contrast, under the 40 J impact, matrix cracking develops rapidly, accompanied by the accelerated propagation of other damage mechanisms. The established FE model predicts the layer‐by‐layer damage process of the laminate under 20 and 40 J impact loads. Three‐dimensional damage envelopes were constructed, which intuitively reflect the spatial distribution characteristics of various damage mechanisms. It is revealed that the load fluctuations on the force‐time curve are closely related to damage evolution: initial inflection is caused by matrix damage, sudden load drops result from matrix failure, and post‐peak load collapse is induced by extensive fiber breakage.