Experimental Validation of an Additively Manufactured Stiffness-Optimized Short-Fiber Reinforced Composite Clevis Joint

  • Y. Saito
  • F. Fernandez
  • D.A. Tortorelli
  • W.S. Compel
  • J.P. Lewicki
  • J. LambrosEmail author


This effort describes experiments for the validation of the response of an additively manufactured stiffness-optimized short-fiber reinforced composite. A Direct Ink Write (DIW) method is used to additively manufacture a clevis joint plate which was designed such that its compliance would be minimized (i.e., stiffness maximized) for far-field axial loading. A unique aspect of the optimization scheme is that it accounts for manufacturing constraints, such as tool turn radius and tool path spacing. Along with the optimized clevis joint plate, additively manufactured 0°–90° and ± 45° composite plates of the same number of layers, as well as a control 0°–90° sample of resin only, were also studied. In addition to far-field load-displacement, near-field strain was monitored using digital image correlation (DIC). The results showed that the optimized plate did indeed exhibit the largest stiffness, based on far-field measurements. DIC-measured strains showed that locally the axial strain component, which is the largest, was also minimized for the optimized specimen, although the other strain components followed different trends. Furthermore, in the experiments it was seen that the optimized design exhibited a nonlinear/hysteretic behavior which is believed to be a consequence of its internal gap/cell structure. This internal structure, which results by optimized placement of material, although explicitly not accounted for in the optimization, may affect global response. Finally, although not a part of the optimization study itself, the failure load for the optimized joint plate was also seen to be the largest of all the cases studied.


Clevis joint plate Manufacturing constraints Optimization Validation Direct ink writing Additive manufacturing 



This work was partially performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344, with Funding from LDRD 15-ERD-030 and LLNLCONF-717640. Document Number: LLNL-JRNL-764135-DRAFT.


  1. 1.
    Gibson I, Rosen D, Stucker B (2015) Additive manufacturing technologies: 3D printing, rapid prototyping, and direct digital manufacturing, 2nd edn. Springer, New York. CrossRefGoogle Scholar
  2. 2.
    Lewicki JP, Rodriguez JN, Zhu C, Worsley MA, Wu AS, Kanarska Y, Horn JD, Duoss EB, Ortega JM, Elmer W, Hensleigh R, Fellini RA, King MJ (2017) 3D-printing of Meso-structurally ordered carbon fiber/polymer composites with unprecedented orthotropic physical properties. Sci Rep 7:43401. CrossRefGoogle Scholar
  3. 3.
    Ghiasi H, Fayazbakhsh K, Pasini D, Lessard L (2009) Optimum stacking sequence design of composite materials part I: constant stiffness design. Compos Struct 90:1–11CrossRefGoogle Scholar
  4. 4.
    Ghiasi H, Fayazbakhsh K, Pasini D, Lessard L (2010) Optimum stacking sequence design of composite materials part II: variable stiffness design. Compos Struct 93(1):1–13CrossRefGoogle Scholar
  5. 5.
    Lozano GG, Tiwari A, Turner C, Astwood S (2016) A review on design for manufacture of variable stiffness composite laminates. Proc Inst Mech Eng B J Eng Manuf 230(6):981–992CrossRefGoogle Scholar
  6. 6.
    Fernandez F, Compel WS, Lewicki JP, Tortorelli DA (2018) Optimal design of fiber reinforced composite structures and their direct ink writing fabrication. Accepted Computer Methods in Applied Mechanics and EngineeringGoogle Scholar
  7. 7.
    Chou T-W (1992) Microstructural design of fiber composites, Cambridge University Press, Ch. 4, p 203Google Scholar
  8. 8.
    Halpin JC (1969) Stiffness and expansion estimates for oriented short fiber composites. J Compos Mater 3(4):732–734CrossRefGoogle Scholar
  9. 9.
    Halpin JC, Kardos JL (1976) The Halpin-Tsai equations: a review. Polym Eng Sci 16(5):344–352CrossRefGoogle Scholar
  10. 10.
    Tucker CL III, Liang E (1999) Stiffness predictions for unidirectional short-fiber composites: review and evaluation. Compos Sci Technol 59(5):655–671CrossRefGoogle Scholar
  11. 11.
    Sutton MA, Orteu J-J, Schreier HW (2009) Image correlation for shape, motion and deformation measurements, chapter 6: in-plane measurements. Springer Science and Business Media, LLC, New York. Google Scholar

Copyright information

© Society for Experimental Mechanics 2019

Authors and Affiliations

  • Y. Saito
    • 1
  • F. Fernandez
    • 2
    • 3
  • D.A. Tortorelli
    • 2
    • 3
  • W.S. Compel
    • 3
  • J.P. Lewicki
    • 3
  • J. Lambros
    • 1
    Email author
  1. 1.Aerospace EngineeringUniversity of Illinois Urbana-ChampaignUrbanaUSA
  2. 2.Mechanical Science and EngineeringUnivesity of Illinois Urbana-ChampaignUrbanaUSA
  3. 3.Lawrence Livermore National LaboratoryLivermoreUSA

Personalised recommendations