Abstract
Nacre from mollusc shells is well known for its high toughness and strength. A key-mechanism for its mechanical performance is the progressive locking generated by the waviness of the mineral tablets it is made of. This allows nacre to generate strain-hardening, arrest cracks and spread inelastic deformations over large volumes before failure. Here we have incorporated a similar feature to short fibers, by machining tapered ends with well defined opening angles on steel pins used to reinforce composites. We performed single-fiber pullout tests on a tapered steel fiber in an epoxy matrix, which showed an improvement in work of pullout (WOP) of up to 27 times for tapered fibers compared to straight fibers. We expect similar increase of toughness for a composite reinforced with tapered fibers. The experimental results indicated the existence of an optimum taper angle to maximize WOP while preventing the brittle fracture of the matrix. An analytical model was derived to understand the interaction between fiber and matrix and to analyze the contributing factors to the WOP. The analytical model captures the trends of tapered fiber pullout and provides useful predictions of the influence of different parameters on WOP.
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© 2013 The Society for Experimental Mechanics, Inc.
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Zhu, D., Humburg, H., Barthelat, F. (2013). Biomimetic Tapered Fibers for Enhanced Composite Toughness. In: Prorok, B., et al. Mechanics of Biological Systems and Materials, Volume 5. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-4427-5_19
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DOI: https://doi.org/10.1007/978-1-4614-4427-5_19
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