Origami, the art of paper folding, has recently seen an upsurge of interest due to its use in guiding the design of lightweight deployable structures. Despite the heavy use of thin films in origami designs, comprehensive mechanical understanding lags behind. This is partly because origami structures are often made from new materials for which bulk material properties are not available. In this work, we show how bending can be used to gather broad mechanical information from thin films, and we show how that information can be applied to more complex structures. Explicitly, we use the technique to measure the Young's modulus and monitor the force recovery of polydimethylsiloxane, polystyrene, and polycarbonate films. Our force recovery data are consistent with the sparse published data available but reveal a previously unreported film thickness dependence. We hypothesize that the thickness dependence is related to the strain gradient present in bending.

Crumpling a sheet creates a unique, stiff and lightweight structure. Use of crumples in engineering design is limited because there are not simple, physically motivated structure-property relations available for crumpled materials; one cannot trust a crumple. On the contrary, we demonstrate that an empirical model reliably predicts the reaction of a crumpled sheet to a compressive force. Experiments show that the prediction is quantitative over 50 orders of magnitude in force, for purely elastic and highly plastic polymer films. Our data does not match recent theoretical predictions based on the dominance of building-block structures (bends, folds, d-cones, and ridges). However, by directly measuring substructures, we show clearly that the bending in the stretching ridge is responsible for the strength of both elastic and plastic crumples. Our simple, predictive model may open the door to the engineering use of a vast range of materials in this state of crumpled matter.

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In this work, we revisit experimentally and theoretically the mechanics of a tape loop. Using primarily elastic materials (polydimethylsiloxane, PDMS, or polycarbonate, PC) and confocal microscopy, we monitor the shape...