Enhancing stiffness and damping characteristics in nacreous composites through functionally graded tablet design

Nacreous composites offer significant potential for applications in structural damping materials, which require simultaneous high stiffness and damping properties. In this study, we propose that the incorporation of functionally graded tablets into nacreous composites can further enhance both stiffness and damping energy dissipation concurrently. Analytical formulae for the loss modulus, storage modulus, and loss factor, validated through a series of finite element analyses, were derived to investigate the effects of variations in tablet modulus, structural geometry, and constituent properties. Our analyses demonstrate that designing a parabolic modulus distribution in the tablets can yield optimal strengthening and damping results. Furthermore, the characteristic modulus variation degree, overlap length, and frequency emerged from the systematic optimization of loss and storage moduli. Additionally, numerical experiments and model predictions demonstrate that the loss modulus of functionally graded nacreous composites surpasses the predetermined design limit and is five times greater than that of existing homogeneous nacreous composites. Combining the developed theoretical model presented here with advanced 3D printing techniques would offer effective guidelines for designing and fabricating high-performance bio-inspired structural damping composites.