Resumo:
Auxetic materials and structures have been attracting attention due to their mechanical
properties, also the notably their high capacity to absorb energy. Some types of auxetic
tubular structures have been studied and designed for application in diverse engineering
fields such as mechanical, aerospace, and medical engineering. In the present study,
inspired by the dragonfly wing shape, a novel auxetic unit cell was developed and applied
in a tubular structure with the goal of proposing a new structure with lower stress
concentration and consequently increased energy absorption. The dragonfly wing (DFW)
shaped unit cells were integrated into a tubular structure, and experimental samples were
produced using an additive manufacturing process. To validate the energy absorption capability
of the novel unit cell, a comparison was made with the classical reentrant auxetic
tubular structure using two different parameters: weight and the number of unit cells,
which were developed in two different DFW structures. The results from the compression
tests showed that the bio-inspired dragonfly wing shape, in both proposed configurations,
demonstrated excellent energy absorption compared to the classical reentrant structure.
Specifically, the structure with the same quantity of unit cells and the structure with the
same weight absorbed 163% and 79% more energy, respectively. Subsequently, an optimization
process was conducted to enhance the mechanical properties of the structure.
An optimization framework was implemented to simultaneously minimize three critical
structural objectives: Poisson’s ratio, mass, and stress. Numerical simulations facilitated
metamodeling via the response surface method, creating surrogate models that accurately
represent each response variable. A metaheuristic optimization technique, the Nondominated
Sorting Genetic Algorithm (NSGA-II), was then employed to optimize these
responses for compression performance. Experimental validation supported the numerical
findings, with two optimized designs proposed. The first design (TOPSIS 1) showed
reductions in Poisson’s ratio by up to 3% and stress by 45%, while the second design
(TOPSIS 2) demonstrated a stress reduction of 537%. Additionally, experimental validation
revealed significant improvements in energy absorption capabilities, with TOPSIS 1
and TOPSIS 2 increasing energy absorption by 58% and 545%, respectively, compared to
the baseline. The present study present the significant potential of bio-inspired auxetic
structures for high complexity applications requiring high energy absorption capacity.