Stochastic honeycomb sandwich cores

J of Applied Polymer Sci

2013

Stochastic honeycombs are a cellular polymer fabricated through a simple melt-stretching process. In this study, five polypropylenes (PP) with varying rheological properties were used to fabricate stochastic honeycombs over a range of densities. Rheology tests were performed to determine the melt behavior, while micro-CT scans were used as a nondestructive characterization technique to determine the internal architecture. The sandwich structure consists of parallel skins separated by a network of interconnected webs. The cross-sectional area decreased from unit area at the skins to a plateau over the middle third of the honeycomb height where the cross-sectional area and total edge length of the webs were relatively constant. The rheological properties of the polymer were found to determine the web length per unit area, while the starting areal density of the polymer controlled the mid-height cross-sectional area. Other features, such as archways and buttresses, act as secondary structures that support the webs. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40074.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Architectural characteristics of stochastic honeycombs fabricated from varying melt strength polypropylenes

J of Applied Polymer Sci

2013

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“…Cellular plastics have become increasingly important for high‐strength low‐weight applications over the last few decades, with more recent attention being turned to fully recyclable products . Polypropylene (PP) stochastic honeycombs have been shown to have similar mechanical properties to conventional PP honeycombs and superior mechanical properties to PP foams . They are fabricated by melting PP between Al platens and then uniaxially stretching the polymer melt to a specified height.…”

Section: Introductionmentioning

confidence: 99%

“…They are fabricated by melting PP between Al platens and then uniaxially stretching the polymer melt to a specified height. Complete sandwich panels can be fabricated out of a single material without blowing agents or adhesives, making them fully recyclable . After cooling, the structure consists of two as‐fabricated face sheets, or skins, separated by a network of interconnected webs.…”

Section: Introductionmentioning

confidence: 99%

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Architecture–process relationships in stochastic honeycombs

J of Applied Polymer Sci

2015

Stochastic honeycomb sandwich panels are fabricated through a simple process of melt-stretching molten polymer blanks. This study mapped their internal architecture over a wide domain of material process space, defined by the areal density and meltstretch rate. The internal architectures were characterized using both topological and geometric parameters: the node density, the total length of webs, the Euler number, and a characteristic fractal area fraction. The mechanical response of the polymer melt was quantified in terms of peak stress and stiffness, along with apparent elongation viscosity. The observed architectures and polymer melt responses were consistent with a varying activated entanglement density in the melt and illustrate how the fabrication conditions can be tuned to obtain a desired architecture.

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Modeling the buckling strength of polypropylene stochastic honeycombs

2014

J Mater Sci