In-plane elastic properties of a novel re-entrant auxetic honeycomb with zigzag inclined ligaments

Auxetic metamaterials have many exceptional mechanical properties due to their counter-intuitive deformation characteristics. However, most studies on auxetic metamaterials focus on in-plane properties while auxetic metamaterials are inevitably affected by out-of-plane forces in practical applications. In this study, the out-of-plane mechanical properties and deformation patterns of a recently proposed auxetic structure, the chiral lattice with circular nodes (NCL), were investigated numerically and experimentally under quasi-static uniaxial compression. It also took truss lattice and traditional chiral lattice (TCL) as benchmarks to compare. The results showed that the energy absorption capacity of the NCL structure in the out-of-plane direction was superior to that of the other two benchmarks. The energy absorption (EA) and specific energy absorption (SEA) of the TCL structure and the truss lattice structure were roughly close, compared with the TCL structure, the EA and SEA of the NCL structure were improved by 34.1% and 13.3%, respectively. In addition, parametric studies were carried out to investigate the effects of geometric parameters and volume fraction of the frame on the structural deformation patterns and mechanical properties. • The out-of-plane compressive behavior of auxetic chiral lattice with circular nodes (NCL) is investigated. • The energy absorption capacity of the NCL in the out-of-plane direction are superior to traditional and truss lattice. • The effects of geometric parameters and volume fraction on the structural mechanical properties are investigated. 

The out-of-plane compressive behavior of auxetic chiral lattice with circular nodes

Fabrication method and dynamic responses of composite sandwich structure with reentrant honeycomb cores

Mechanical properties of aluminum foam filled re-entrant honeycomb with uniform and gradient designs

Experimental and numerical study on the ballistic impact resistance of the CFRP sandwich panel with the X-frame cores

A novel composite double-arrow auxetic structure was designed and fabricated in this paper. The ballistic impact experiments were conducted using one stage gas gun to study the effects of the relative density on the impact responses and failure mechanism. The impact process of the projectile was recorded by a high-speed camera. The ballistic limit velocities, damage area and failure mechanism of composite double-arrow auxetic structure with different relative densities were compared and analyzed. The anti-penetration performances of composite double-arrow auxetic structure were evaluated and discussed based on the experimental results. In order to simulate and reveal the damage evolution process, the finite element model was used to simulate the ballistic impact process of composite double-arrow auxetic structure. The ballistic limit velocities and failure modes of the simulation results were compared with that of the experimental results. The comparison indicated that the simulated results were in agreement with the experimental results. 

Ballistic impact responses and failure mechanism of composite double-arrow auxetic structure

In present study, the foam-filled composite double-arrow auxetic structures were obtained by the mold hot pressing method, bonding technology and stirring foaming process. The ballistic impact tests of the foam-filled composite double-arrow auxetic structure were carried out, and the effect of foam filling on the ballistic impact response of the composite double-arrow auxetic structure was analyzed. The ballistic impact test results indicated that the ballistic limit velocity of the foam-filled double-arrow auxetic structure with the relative density of 16.66% was 121.30 m/s. With the increase of the incident kinetic energy of the projectile, the specific energy absorption of the foam-filled auxetic structure increased first and then decreased, and remained near the horizontal line of 550 J/kg at last. Compared to unfilled auxetic structure, the ballistic limit velocity of foam-filled auxetic structure increased by 6.12% and the energy absorption property of foam-filled auxetic structure was improved. The ballistic impact performances of foam-filled composite double-arrow auxetic structures were studied by finite element method. The simulation results of foam-filled auxetic structure with RD=16.66% were in good agreement with the experimental results. The simulation results demonstrated that the ballistic limit velocities of foam-filled composite auxetic structures with relative densities of 9.08%, 16.66% and 23.06% were 86.74 m/s, 120.60 m/s and 152.80 m/s, respectively. Furthermore, the increase of relative density had a positive effect on improving the anti-penetration performance of foam-filled composite auxetic structures. • A novel foam-filled composite double-arrow auxetic structure was fabricated. • The ballistic impact experiments were conducted to evaluate the impact properties. • The effect of foam filling on the ballistic impact response was analyzed. • The finite element model was used to simulate the ballistic impact process. 

Wanchun Yang

Papers

Ballistic impact responses and failure mechanism of composite double-arrow auxetic structure

Ballistic impact analyses of foam-filled double-arrow auxetic structure