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Abstract
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This study presents a comprehensive dynamic analysis of dual-bonded sandwich beams featuring micro-voided cores and nanoengineered carbon nanotube (CNT)-gradated composite faces. The proposed structure departs from conventional sandwich concepts by integrating a quasi-brittle lightweight core whose sti ness and density are modi ed by uniformly distributed micro-voids with functionally tailored nanoscale reinforcement in the facesheets. The beam is supported by three discrete rows of linear elastic springs to model partial or elastic foundations typically encountered in civil, aerospace, and marine applications. The formulation accounts for the coupled e ects of nanoscale gradation, core micro-porosity, and interfacial bonding sti ness, providing a uni ed framework for vibration tailoring of multilayer composite structures. Five CNT distribution pro les and three volume fractions are examined to reveal how the synergy between material gradation and micro-void e ects inuences the modal response. Numerical results show that increasing the void index from 0.0 to 0.8 increases the rst three natural frequencies by 20{23% due to mass reduction dominance, while enhancing the CNT volume fraction from 0.12 to 0.28 yields up to 30% higher frequencies owing to nanoscale sti ening. The ndings introduce a new perspective for designing lightweight and high-sti ness sandwich systems where vibration control and structural integrity are critical, particularly in smart bridges, modular frames, o shore platforms, and blast-resistant panels
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