Designing tough isotropic structural composite using computation, 3D printing and testing

Abstract

Staggered platelet composites found in nature, such as nacre, bone, and conch-shell, exhibit a remarkable combination of high toughness, strength, and stiffness, and have inspired the development of bio-inspired composites mimicking their characteristic features. However, those excellent mechanical properties are primarily observed under specific loading conditions due to their mechanical anisotropy, which originates from the aligned microstructures consisting of high aspect ratio inclusions. In this study, we combine numerical simulations and 3D-printing to propose a design strategy of isotropic twodimensional structural composites consisting of stiff and soft constituents that are arranged in square, triangular, and quasicrystal lattices. For these relatively isotropic structures, the soft tile/stiff boundary configuration significantly outperforms the stiff tile/soft boundary configuration in terms of normalized toughness, strength, and stiffness with respect to the simple rule of mixture estimates for each, because the former provides more extrinsic toughening mechanisms and effectively lower the stress concentration near the crack tip. The quasicrystal lattice offers the best isotropy in elastic response, while its absolute values of stiffness, strength, and toughness turn out to be similar or lower than those of triangular lattice composites due to more irregular stress distribution. In contrast, for the highly anisotropic staggered platelet structure, the stiff tile/soft boundary configuration significantly outperforms the inverted one, owing to its unique load-transfer mechanism which relies primarily on the shear-lag effect.

3D‐Printed Anisotropic Polymer Materials for Functional Applications

“…[ 138 ] Yet, 3D isotropy is required in some cases where the materials need to sustain multiple loading modes with similar magnitudes along all the directions. [ 139 ] MJF is an effective technique that can improve layer adhesion along the z ‐direction by using fusing agent that is able to absorb energy through the process and provide the right environment for layers to fuse together. Although the reduction of anisotropy has been worked on, in pursuit of various functionalities, efforts have also been made in achieving controllable anisotropy.…”

Modelling the interphase of 3D printed photo-cured polymers

“…Among the many available techniques, Polyjet-based manufacturing is attracting a lot of interest since it allows the production of complex architectures by employing more than one material at the same time, whose properties can be widely different: for instance, a hard, glassy polymer coupled with a soft, rubbery one, with elastic moduli at room temperature differing by about three orders of magnitude. This feature has been recently exploited by several authors to produce bio-inspired composite materials [1,[5][6][7][8][9][10][11][12]. Briefly, Polyjet 3D printing is a layer-by-layer method where one or more photo-curable liquid polymers are jetted in the form of droplets through several printing nozzles onto a build tray [1].…”

Design of an auxetic cellular structure with different elastic properties in its three orthogonal directions

“…7,20,21 This type of structure has been extensively studied due to the attractive properties that can be achieved during design, such as high resistance, low density and the ability to absorb energy. [22][23][24][25][26] Auxetic materials are a type of structure that has attracted great attention, since their concomitant properties make them promising for use in a wide range of fields such as automotive and structural engineering. 27,28 Unlike conventional materials, auxetic materials have a negative Poisson's ratio, i.e.…”