MODELING AND ANALYSIS THROUGH CLASSICAL, PURE WAVE-BASED, AND HYBRID INTEGRATION APPROACHES, AND EXPERIMENTAL VALIDATION OF DAMAGE-INDUCED GFRP LAMINATE PU FOAM SANDWICH STRUCTURES

Sandwich composite structures are widely employed in automotive, aerospace and marine industries due to their exceptional stiffness-to-weight ratio, strength-to-weight ratio, vibration attenuation, enhanced aero-elastic characteristics and energy absorption capabilities. Accurate prediction of their dynamic behavior under damaged conditions remains a major challenge because conventional classical models fail to capture high-frequency dispersion effects, while pure wave-based models often neglect realistic boundary conditions. This study presents a unified hybrid modeling framework based on classical vibration theory with wave propagation analysis to evaluate the dynamic response of Glass Fiber-Reinforced Polymer (GFRP) sandwich panels across a wide frequency range. The hybrid frequency-domain equations were numerically implemented using Python to extract frequency-amplitude response enabling efficient computation of broadband Frequency Response Functions (FRFs). Experimental modal testing was conducted under Clamped-Free-Free-Free (cantilever) boundary conditions for undamaged, core-damaged, delaminated, and impact-damaged specimens. The numerically predicted FRFs were systematically correlated with experimental results. The results indicate that the hybrid models accurately capture resonant peak shifts, damping variations, and stiffness degradation effects with significantly reduced prediction error. The proposed framework provides a robust and computationally efficient tool for dynamic analysis and reliable vibration-based structural health monitoring of sandwich composite structures.