Biomimetic Case Exploration: Potential Improvements to Ropes for Exercise Equipment on Long Duration Space Missions

Kelly Siman, Elena Stachew, Sebastian Engelhardt, Sara SantosNIEA Summit 2017 October 5, 2017 Ohio Aerospace Institute

Introduction:

▲ Rocky exercise device [3]

• The use of ropes and cables in space hold vital multifunctional objectives, including exercise tensile resistance, vibrational isolation of equipment, and extravehicular activity (EVA) [1,2]

• Ropes tested for use in exercise equipment typically failed due to poor tensile strength, flex fatigue and abrasion from pulleys during life-cycle testing. Ropes that failed in use during exercise on the International Space Station (ISS) were due to low tensile strength, stress concentrations and bending [2]

• Rope failure causes astronauts to take time out of other mission activities to fix equipment and for crucial exercise activities to temporarily halt. Extending the life-span of ropes and cables would prolong the need for replacement, reduce or eliminate equipment interruption, and has the potential to reduce extra ropes (and weight) on mission payloads [1,2]

• Through a biomimetic approach, the group sought to redesign the rope through principle abstraction of natural models related to essential rope and cable functions, as well as critical failure points

▲ Vectran rope wedged in pulley [2]

▲ Rope testing at ZIN Technologies

Outlook: Acknowledgements:

References:[1] Moore, C., Svetlik, R., & Williams, A. (2017) Practical applications of ropes and cables in the ISS countermeasures system. Proceedings of 2017 IEEE Aerospace Conference. Yellowstone Conference Center, Big Sky, Montana. doi: 10.1109/ AERO.2017.7943700. [2] Moore, C., Svetlik, R., & Williams, A. (2017). Designing for reliability and robustness in international space station exercise countermeasures systems. Proceedings of 2017 IEEE Aerospace Conference. Yellowstone Conference Center, Big Sky, Montana. doi: 10.1109/AERO.2017.7943563. [3] Image taken from: https://www.nasa.gov/feature/exercise-device-for-orion-to-pack-powerful-punch [4] Flammang, B. E., Alben, S., Madden, P. G., & Lauder, G. V. (2013). Functional morphology of the fin rays of teleost fishes. Journal of Morphology 274 (9), 1044-1059. doi: 10.1002/ jmor.20161. [5] Fratzl, P., Weinkamer, R. Nature’s hierarchical materials. (2007). Progress in Materials Science, 52(8), 1263-1334. doi: 10.1016/j.pmatsci.2007.06.001. [6] Fidelis, M.E.A., Pereira, T.V.C., Gomes, O.F.M., Silva, F.A., Filho, R.D.T (2013). The effect of fiber morphology on the tensile strength of natural fibers. J Mater Res Technology, 2(2),149–157. doi: 10.1016/j.jmrt.2013.02.003. [7] Habibi, M.K., Lu, Y. (2014). Crack Propagation in Bamboo’s Hierarchical Cellular Structure. Sci. Rep. 4(5598). doi:10.1038/srep05598.

[8] K.L. Pickering, M.G. Aruan Efendy, T.M. Le. (2016). A review of recent developments in natural fibre composites and their mechanical performance. Composites Part A: Applied Science and Manufacturing, 83, 98-112. doi: 10.1016/j.compositesa.2015.08.038. [9] Wegst, U.G.K., Bai, H., Saiz, E., Tomsia, A.P., Ritchie, R.O. (2014). Bioinspired structural materials. Nat. Mater. 14, 23–36. doi:10.1038/nmat4089. [10] Vihar, Boštjan. (2015). Mimicking the abrasion resistant sandfish epidermis (Master’s thesis, RWTH Aachen University, Aachen, Germany). Retrieved from: https:// publications.rwth-aachen.de/record/538206. [11] Baumgartner, W., Saxe, F., Weth, A., Hajas, D., Sigumonrong, D., Emmerlich, J., Singheiser, M., Bohme, W., Schneider, J.M. (2007). The Sandfish’s Skin: Morphology, Chemistry and Reconstruction. Journal of Engineering 4(1), 1-9. doi: 10.1016/S1672-6529(07)60006-7. [12] Image taken from: http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2014/5/27/1401185342046/The-earthworm-way---blind-014.jpg [13] Yan, Y.Y., Hull, J.B., Ren, L., Li, J., 2004. Electro-osmotically driven flow near a soil animal body surface and biomimetics. In Design and Nature II (Eds: Collins, M.W., Brebbia, C.A.), WIT Press, pp. 217-225. [14] Cong, Q., Wu, L., Ren, L., Chen, B., 1995. The principled experiment of reducing soil adhesion and scouring soil by non-smooth surface electro-osmosis. Transactions of the Chinese Society of Agricultural Engineering, 11(3), 19-23 .

Hierarchical structuring:• Natural fiber structures are hierarchical and the “exceptional mechanical properties are believed to be due to a functional adaptation of the structure at all levels of hierarchy” [5]. Various lumen to cell wall ratios provide a diversity of tensile and functional strengths, with low density [6]

▲ Transversal cross-section of bamboo cellular structure [7] and 3D printed concept of fibre lumen-cell structure based on natural fibres

• Overall, natural fiber structures cause less abrasion to equipment than synthetic fibres [8]

• Natural fiber structures are less durable than synthetic fibre composites, but can be vastly improved with a hybrid methodology of combining synthetic treatments to the natural fiber structure

▲ Hierarchical structure of bamboo [9]▲ Ashby plot of the specific strength and stiffness for natural and synthetic materials [9]

Abrasion resistant coatings:• To reduce internal fiber, sheath or pulley abrasion, the sandfish was examined as a possible biological model as it is known for its ability to essentially swim in desert sand, albeit with very smooth scales

• It is suggested that the surface structure of the sandfish is not responsible for its low friction behavior, unlike several other species of snakes

▲ Sandfish species found in North Africa and the Arabian Peninsula [10]

where the structure is responsible for frictional anisotropy for movement [11]

• Chemical analysis shows that the scales are composed of glycosylated B-keratins with high sulfur content. This unique chemical composition of glycosylated B-keratins has not been found in other reptilian scales thus far and significantly affects the low friction properties of sandfish scales [11]

• It is possible to modify synthetic surfaces (such as glass, PMMA or acrylic) with key glycans, isolated from sandfish scales. M5-M9 glycans are the closest known native structures found in the sandfish epidermis

▲ Effect of glycan bonding on modified acrylic lacquers provided by BASF [10]

Our group would like to thank Dr. Petra Gruber (University of Akron) and Gail P. Perusek (NASA Glenn Research Center) for their guidance and support. The group would also like to thank Dr. Christopher Dellacorte (NASA Glenn Research Center), Dr. Henry Astley (University of Akron), Dr. Ali Dhinojwala (University of Akron) and Dr. Paul Schiller (Timken Engineered Surface Laboratory) for their additional focus meetings with the group. Lastly, the group would like to thank Zin Technologies for the tour of their facilities and Dr. Peter Niewiarowski and Dr. Christopher Miller for their in-class suggestions

• Explore hierarchical structure combination for optimal strength, durability, and flexibility

• Investigate whether chemical functionality of the sandfish skink scale is specifically attuned to silicate particle interactions and test isolated glycan coating on technical textile rope for reduced abrasion effect

• Consider additional bending angles and different shapes of the individual segments to optimize tension resistance and prototype a pig intestine inspired rope sheath

• Build and test prototype pulleys that incorporates alternating electrodes for electro osmosis. 3-D print and test possible pulley case designs

Pulley lubrication:• Pulley lubrication could further reduce rope abrasion. However, under zero-G conditions a mechanism to keep the lubricant on the pulley surface has to be developed• The earthworm creates a negative electric potential (40 mV) between its skin and the soil to attract water molecules for lubrication while moving (electro-osmosis) [13]

• Positive and negative poles are located on neighboring segments allowing a dynamic movement of water molecules while water always tends to migrate to the negative pole [13]

• The principles of electro osmosis have been applied to bulldozer blades by Cong et al., resulting in a 32% decrease of resistance while digging [14]

▲ The earthworm and the principles of electro-osmosis [12,13]

▲ Positioning of electrodes to induce electro-osmosis on bulldozer blades and other applications [14]

• A mechanical solution incorporating an enclosed pulley case with a pressure sensitive semi-permeable membrane may be considered for future designs

▲ Possible design of a pulley case

Rope segmentation:• Segmentation in ropes would allow for localized repairs, extension/shortening and customization for specific applications (reduction of weight and materials)• Fish fins move nearly seamlessly through water, which is supported by a 55° bending angle of the single fish fin segments [4]. We used this principle for the design of mechanical links for segmented ropes

▲ 3-D printed model of a segmented rope prototype

• The structure of a pig’s large intestine, although optimized to maximize absorption of water, is used as the preferred structure for the sheath. The outer wall is smooth to reduce abrasion with the pulley, while the inner wall has interstices. The inner wall structure allows the sheath to accommodate the bending of the chain while also shaping around each individual link ▲ Pig intestine as model for rope sheath

▲ Morphology of the segmentation of fish fin [4]