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Investigation into Z-Pin Reinforced Composite Skin/Stiffener Debond under Monotonic and Cyclic Bending

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Abstract

Skin/stiffener debonding has been a longstanding concern for the users of stiffened composite panels in long-term service. Z-pinning technology is an emerging solution to reinforce the composite assembly joints. This work experimentally characterizes the progressive debonding of Z-pinned skin/stiffener interface with the skin under static bend loading. The three-stage failure process is identified as: flange edge debonding, pin/laminate debonding, and ultimate structural failure. Three different distribution patterns were compared in terms of the static debonding properties revealed the affirmative fact that locating pins in high normal stress regions, that is close to the flange edges in skin/stiffener structures, is more beneficial to utilize the full potential of Z-pinning reinforcement. The unit strip FE model was developed and demonstrated effective to analysis the effect of Z-pin distribution on the ultimate debond load. On the other hand, the evolution of fatigue cracks at Z-pinned skin/flange interface was investigated with a series of displacement-controlled fatigue bending tests and microscopic observations. Results show that Z-pinning postpones crack initiations at low displacement levels, and the remarkable crack-arresting function of pins enables the structure a prolonged fatigue life. However, pins become less effective when the maximum displacement exceeds the crack initiation level due to gradually pullout of pins.

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Acknowledgements

The work was funded by the Aeronautical Science Foundation of China (grant number 2015ZE52049) and China Scholarship Council. Also appreciation goes to the colleagues from Concordia Center for Composites, Concordia University, for technical support.

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Authors and Affiliations

  1. College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016, China

    Xiangyang Zhang, Yong Li, Jun Xiao & Qiyi Chu

  2. Concordia Center for Composites, Department of Mechanical and Industrial Engineering, Concordia University, Montreal, QC, H3G 1M8, Canada

    Xiangyang Zhang & Suong Van Hoa

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  1. Xiangyang Zhang
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  2. Yong Li
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  3. Suong Van Hoa
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  4. Jun Xiao
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Correspondence to Yong Li.

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Zhang, X., Li, Y., Van Hoa, S. et al. Investigation into Z-Pin Reinforced Composite Skin/Stiffener Debond under Monotonic and Cyclic Bending. Appl Compos Mater 25, 203–219 (2018). https://doi.org/10.1007/s10443-017-9640-6

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  • DOI: https://doi.org/10.1007/s10443-017-9640-6

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