Abstract
A highly ordered, hexagonal, nacre-like composite stiffness is investigated using experiments, simulations, and analytical models. Polystyrene and polyurethane are selected as materials for the manufactured specimens using laser cutting and hand lamination. A simulation geometry is made by digital microscope measurements of the specimens, and a simulation is conducted using material data based on component material characterization. Available analytical models are compared to the experimental results, and a more accurate model is derived specifically for highly ordered hexagonal tablets with relatively large in-plane gaps. The influence of hexagonal width, cut width, and interface thickness are analyzed using the hexagonal nacre-like composite stiffness model. The proposed analytical model converges within 1% with the simulation and experimental results.
Highlights
Nature presents several structures optimized through evolution
We present a model that is suitable for hexagonal-shaped tablets inspired from the work of Barthelat [30] with the use of stiffness of volumes in series, and the work of Bar-On and Wagner [34] and Jaeger and Fratzl [35] with the use of Voigt model to calculate the stiffness of partial volumes of a representative volume element (RVE)
Thin polystyrene films of 135 μm thickness with a measured stiffness of 2.65 GPa and polyurethane liquid resin mixture with resulting stiffness measured to be 0.35 GPa are combined composite materials to investigate nacre-like structure stiffness
Summary
Nature presents several structures optimized through evolution. Nacre is currently a central inspiration for biomimetic structure design and manufacturing methods for toughened ceramics, as showcased by Bouville [1]. Natural nacre consists of calcium carbonate bonded by protein molecules and polysaccharides [2]. This construction of overlapping tablets increases the toughness of the material by two orders of magnitude or more than bulk brittle material, as described by Bathelat et al [3]. The most attractive feature in this construction is that it maintains considerable stiffness and strength, as measured by Wang et al [4] and Currey [5]. This feature is becoming attractive to composite engineers for the development of novel composite types, which has been an active research area for the last two decades. Budarapu [6] further adds that the nacre structure resists crack propagation running across the tablets and main deformation of the structure, which is due to tablet sliding until pull-out
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