Time-domain analysis of delaminated sandwich structures: Viscoelastic and frictional damping effects

Delamination is a critical damage mode in laminated structures that significantly affects structural integrity, requiring effective detection strategies. This study investigates the dynamic behavior of delaminated sandwich beams, focusing on the interaction between viscoelastic and frictional damping mechanisms. While traditional nondestructive testing methods have limitations, vibration-based techniques offer a promising alternative for structural health monitoring. As the first part of a two-part investigation, this paper presents a time-domain finite element analysis to simulate the dynamic response of delaminated beams under sine-sweep excitation. The analysis captures complex interfacial interactions and establishes a baseline for assessing delamination-induced changes. A follow-up study will address the frequency-domain response, focusing on modal characteristics of pristine and damaged structures and evaluating the contributions of material and frictional damping effects. The findings enhance our understanding of damping behavior in delaminated structures, showing that material damping contributes more to overall energy dissipation than frictional damping under the studied conditions. A sensitivity analysis reveals that energy-based indicators related to both damping mechanisms respond to variations in delamination size, pattern, and location, each showing distinct sensitivity trends. These insights contribute to developing more sensitive and robust vibration-based damage detection methods, with modal damping proposed as a potential damage index.