Abstract
Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA) using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.
Highlights
Bone has the intrinsic ability of self-healing in the case of being damaged in small areas
The yield stress was found by finding the maximum stress, σmax, in the finite element (FE) model and substituting it in Equation (40)
Since the experimental data provided by Gibson and Ashby [10,27] are only presented for very small relative densities (μ ă 0.02) and the experimental results obtained in this paper cover relatively large relative densities (0.2 ă μ ă 0.55), the diagram of each mechanical behavior is plotted in two ranges of relative densities: one from 0 to 0.02, and the other from 0 to 0.5
Summary
Bone has the intrinsic ability of self-healing in the case of being damaged in small areas. In large bony defects, bone loses its ability to repair itself by regeneration of new bony tissue. While autologous bone grafting is known as the gold standard in orthopaedic surgery, it has some drawbacks such as limited bone stack and donor site mordibility [1]. Porous titanium and titanium alloy scaffolds have been thoroughly investigated due to their excellent biocompatibility and corrosion resistance, low stiffness (which is necessary for avoiding stress shielding), and good bone regeneration performance. Additive manufacturing techniques have made it possible to fabricate scaffolds with precisely controlled micro-architecture. Several 3D unit cell types have been suggested and tested
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