Poisson's Ratio for Honeycomb Sandwich Cores

Hoffman, George A.

doi:10.2514/8.7765

Cited by 12 publications

(7 citation statements)

References 2 publications

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“…In particular, strain amplification can be obtained by uniform lattices (one type of unit cell) [ 5 , 6 ], whereas zero strain perpendicular to the force direction (Poisson’s ratio of zero) can be achieved by combining different unit cells [ 7 ]. Meanwhile, the mechanical properties and residual stresses depend on the geometric parameters and loading direction and can be highly anisotropic in-plane and out-of-plane [ 8 , 9 , 10 , 11 ]. Of particular interest are the in-plane properties of Poisson’s ratio, Young’s modulus, and strength, which can be modified by geometric parameters as angle, strut thickness, etc.…”

Section: Introductionmentioning

confidence: 99%

Advanced Estimation of Compressive Strength and Fracture Behavior in Ceramic Honeycombs by Polarimetry Measurements of Similar Epoxy Resin Honeycombs

et al. 2022

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Finding a non-destructive characterization method for cellular ceramics’ compressive strength and fracture behavior has been a challenge for material scientists for years. However, for transparent materials, internal stresses can be determined by the non-destructive photoelastic measurements. We propose a novel approach to correlate the photoelastic stresses of polymer (epoxy resin) prototypes with the mechanical properties of ceramics (alumina). Regular and inverse epoxy honeycombs were 3D-printed via stereolithography with varying structure angles from −35° to 35°, with negative angles forming an auxetic and positive hexagonal lattice. Photoelastic measurements under mechanical loading revealed regions of excess stress, which directly corresponded to the initial fracture points of the ceramic honeycombs. These honeycombs were made by a combination of 3D printing and transfer molding from alumina. The photoelastic stress distribution was much more homogeneous for angles of a smaller magnitude, which led to highly increased compressive strengths of up to 446 ± 156 MPa at 0°. By adapting the geometric structural model from Gibson and Ashby, we showed that we could use a non-destructive technique to determine the compressive strength of alumina honeycombs from the median photoelastic stress measured on similar epoxy honeycomb structures.

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Section: Introductionmentioning

confidence: 99%

Advanced Estimation of Compressive Strength and Fracture Behavior in Ceramic Honeycombs by Polarimetry Measurements of Similar Epoxy Resin Honeycombs

et al. 2022

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“…Concurrently, ceramic honeycombs have highly anisotropic properties that vary greatly in-plane and out-of-plane [13,14] and are permeable in only one direction. However, an open-pore cell structure with permeability in all spatial directions would be preferred for applications such as hydrophones and medical implants [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Energy-Reduced Fabrication of Light-Frame Ceramic Honeycombs by Replication of Additive Manufactured Templates

Köllner,

Niedermeyer,

Vermes

et al. 2023

Materials

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Ceramic components require very high energy consumption due to synthesis, shaping, and thermal treatment. However, this study suggests that combining the sol–gel process, replica technology, and stereolithography has the potential to produce highly complex geometries with energy savings in each process step. We fabricated light-frame honeycombs of Al2O3, Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT), and BaTiO3 (BT) using 3D-printed templates with varying structural angles between −30° and 30° and investigated their mechanical and piezoelectric properties. The Al2O3 honeycombs showed a maximum strength of approximately 6 MPa, while the BCZT and BaTiO3 honeycombs achieved a d33 above 180 pC/N. Additionally, the BCZT powder was prepared via a sol–gel process, and the impact of the calcination temperature on phase purity was analyzed. The results suggest that there is a large energy-saving potential for the synthesis of BCZT powder. Overall, this study provides valuable insights into the fabrication of complex ceramic structures with improved energy efficiency and enhancement of performance.

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“…low effective density. To further extend the range of achievable mechanical properties, much research over the previous decades has explored alternative geometries to the standard honeycomb shaped cellular core, and it has been shown that Poisson's ratios from ν = −1 to 1 [13][14][15] can be realised by altering the unit cell geometry. Zero Poisson's ratio cores are of particular interest in morphing structures, as they allow for large strains in the morphing direction while eliminating the Poisson's effects that would lead to undesired coupled deformations in the non-morphing directions.…”

Section: Introductionmentioning

confidence: 99%

Manufacturing and characterisation of 3D printed thermoplastic morphing skins

Heeb

Dicker

Woods

2022

Smart Mater. Struct.

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Morphing aircraft are one promising solution to reducing the aviation industry's environmental impact because they can make aircraft more aerodynamically efficient, thereby reducing greenhouse gas emissions. The design of morphing skins is inherently challenging due to the competing design constraints of needing to be stiff out-of-plane to resist pressure loads while being compliant in-plane to minimise actuation energy. Previous work by these authors introduced the novel concept of Geometrically Anisotropic Thermoplastic Rubber (GATOR) morphing skins that take advantage of multi-material 3D printing and structural scaling laws to allow for better compromises between these competing design constraints. In this work, multi material Fused Filament Fabrication (FFF) methods were used to 3D print the proposed GATOR sandwich panels from two different stiffnesses of thermoplastic polyurethane to demonstrate the manufacturing process and experimentally quantify the performance of some simple embodiments of the GATOR concept. The panels were mechanically tested to determine their flexural and extensional stiffnesses. Results show that the panels can be extended to a stretch ratio of λ = 1.6 with a linear response at low stretch ratios. The results from the flexural experiments show that the flexible face sheets are capable of withstanding some compression before buckling, which results in a linear behaviour at small forces. These results show the promise of the GATOR skin concept and motivate future development of designs that further exploit the underlying principles of the concept.

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Poisson's Ratio for Honeycomb Sandwich Cores

Cited by 12 publications

References 2 publications

Advanced Estimation of Compressive Strength and Fracture Behavior in Ceramic Honeycombs by Polarimetry Measurements of Similar Epoxy Resin Honeycombs

Advanced Estimation of Compressive Strength and Fracture Behavior in Ceramic Honeycombs by Polarimetry Measurements of Similar Epoxy Resin Honeycombs

Energy-Reduced Fabrication of Light-Frame Ceramic Honeycombs by Replication of Additive Manufactured Templates

Manufacturing and characterisation of 3D printed thermoplastic morphing skins

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