Natural Frequency and Thermal Buckling Behaviour of Delaminated Composite Plate

Delamination is a critical damage mechanism in laminated composites that significantly reduces structural stiffness, leading to adverse effects on dynamic behaviour. This study investigates the impact of delamination on the natural frequency of moderately thin composite panels using a nonlinear finite element model. The model is developed based on first-order shear deformation theory, von Karman strain-displacement relations, and the principle of virtual work to capture the dynamic response of delaminated panels accurately. The delaminated region is modelled using an effective stiffness approach, which adjusts the local stiffness properties to reflect the degradation due to damage. The proposed model provides robust thermomechanical property estimates for delaminated composites, enabling precise evaluation of the shifts in natural frequency under thermal and mechanical loading. Numerical simulations demonstrate the influence of delamination length, location on the natural frequency, offering insights into the sensitivity of composite structures to delaminationinduced degradation. This study contributes to improved predictive capabilities for the dynamic performance of damaged composite structures, supporting the development of more resilient and reliable composite materials.