Folding behavior of thermoplastic hinges fabricated with polymer extrusion additive manufacturing

  • Cesar Omar Balderrama-ArmendarizEmail author
  • Eric MacDonald
  • David A. Roberson
  • Leopoldo Ruiz-Huerta
  • Aide Maldonado-Macias
  • Esdras Valadez-Gutierrez
  • Alberto Caballero-Ruiz
  • David Espalin


Due to the layer-by-layer nature of additive manufacturing, fabricated parts suffer from an anisotropic behavior with reduced mechanical performance when compared to traditional manufacturing. One specific mechanical property, folding endurance, requires both low flexural strength and simultaneously high elongation to achieve the flexibility needed to sustain repetitive bending. The present work provides an analysis of selected thermoplastics’ flexural capacity, including nylon (PA), polyethylene terephthalate (PETG), polylactide (PLA), thermoplastic polyurethane (TPU), polypropylene (PP), polyethylene (PE), and a TPR blend (ABSMG94: SEBS-g-MA 25:75), in order to evaluate the maximum number of folding cycles and load capacity sustained by a living hinge. A fractographic analysis was performed using scanning electron microscopy and computed tomography. Similar to the performance of injected molded products, the experimental results demonstrated that three of the tested materials behaved well in the context of a large number of folding cycles prior to an eventual detachment into two pieces; TPR blend, 244,424 cycles; PP endured one million cycles; and TPU, more than two million cycles, while the remaining materials failed to survive more than 1000 cycles. The hinges failure analysis revealed a wide variety of fracture morphologies and failure modes. In regard to the load capacity, PLA, PETG, and nylon provided the highest results in the ultimate strength of an axial static force applied (790.61 N, 656.06 N, and 652.75 N respectively), while the TPR blend was the highest (398.44 N) of the elastomeric materials (PP, TPU, and TPR blend). The evaluated materials demonstrated enough flexibility for use in specific applications such as stretchable electronics and wearable applications.


Polymer extrusion Additive manufacturing Folding endurance Flexible 3D printed materials Flexible Aplications Fused deposition 



The research presented here was conducted in the Rapid Prototyping Lab at the Universidad Autónoma de Ciudad Juárez (Autonomous University of Ciudad Juarez) in Collaboration with The University of Texas at El Paso (UTEP) in the W.M. Keck Center for 3D Innovation. The Friedman Chair for Manufacturing at Youngstown State University also supported the work.

Funding information

Funding for this work was provided by the AFOSR through the Young Investigator Program (YIP) under grant number FA9550-14-1-0260 and the Defense University Instrumentation Program (DURIP) under grant number FA9550-15-1-0312.


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Copyright information

© Springer-Verlag London Ltd., part of Springer Nature 2019

Authors and Affiliations

  • Cesar Omar Balderrama-Armendariz
    • 1
    • 2
    Email author
  • Eric MacDonald
    • 3
  • David A. Roberson
    • 4
  • Leopoldo Ruiz-Huerta
    • 2
    • 5
  • Aide Maldonado-Macias
    • 6
  • Esdras Valadez-Gutierrez
    • 1
  • Alberto Caballero-Ruiz
    • 2
    • 5
  • David Espalin
    • 7
  1. 1.Rapid Prototyping LaboratoryUniversidad Autónoma de Ciudad JuárezCiudad JuarezMexico
  2. 2.National Laboratory for Additive and Digital Manufacturing (MADiT)MexicoMexico
  3. 3.Advanced Manufacturing Research CenterYoungstown State UniversityYoungstownUSA
  4. 4.Polymer Extrusion LabThe University of Texas at El PasoEl PasoUSA
  5. 5.Instituto de Ciencias Aplicadas y TecnologíaUniversidad Nacional Autónoma de MéxicoCd. Mx.Mexico
  6. 6.Department of Industrial and Manufacturing EngineeringUniversidad Autónoma de Ciudad JuárezChihuahuaMexico
  7. 7.W. M. Keck Center for 3D InnovationThe University of Texas at El PasoEl PasoUSA

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