Design Innovation Paper

Additive Manufacturing of Structural Cores and Washout Tooling for Autoclave Curing of Hybrid Composite Structures

[+] Author and Article Information
Daniel-Alexander Türk

Department of Mechanical and Process Engineering,
Product Development Group Zürich,
ETH Zurich,
Zurich 8092, Switzerland
e-mail: dturk@caltech.edu

Andreas Ebnöther, Mirko Meboldt

Department of Mechanical and Process Engineering,
Product Development Group Zürich,
ETH Zurich,
Zurich 8092, Switzerland

Markus Zogg

Inspire AG,
Technoparkstrasse 1,
Zürich 8005, Switzerland

1Corresponding author.

2Present address: Graduate Aerospace Laboratories, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125.

Manuscript received December 20, 2017; final manuscript received May 19, 2018; published online July 9, 2018. Assoc. Editor: Zhijian J. Pei.

J. Manuf. Sci. Eng 140(10), 105001 (Jul 09, 2018) (14 pages) Paper No: MANU-17-1796; doi: 10.1115/1.4040428 History: Received December 20, 2017; Revised May 19, 2018

This paper presents a study combining additive manufactured (AM) elements with carbon fiber-reinforced polymers (CFRP) for the autoclave curing of complex-shaped, lightweight structures. Two approaches were developed: First, structural cores were produced with AM, over-laminated with CFRP, and co-cured in the autoclave. Second, a functional hull is produced with AM, filled with a temperature- and pressure-resistant material, and over-laminated with CFRP. After curing, the filler-material is removed to obtain a hollow lightweight structure. The approaches were applied to hat stiffeners, which were modeled, fabricated, and tested in three-point bending. Results show weight savings by up to 5% compared to a foam core reference. Moreover, the AM element contributes to the mechanical performance of the hat stiffener, which is highlighted by an increase in the specific bending stiffness and the first failure load by up to 18% and 310%. Results indicate that the approaches are appropriate for composite structures with complex geometries.

Copyright © 2018 by ASME
Your Session has timed out. Please sign back in to continue.


Evans, A. G. , 2001, “ Lightweight Materials and Structures,” MRS Bull., 26(10), pp. 790–797. [CrossRef]
Davies, J. M. , 2001, Lightweight Sandwich Construction, Wiley-Blackwell, Oxford, UK. [CrossRef]
Herrmann, A. S. , Zahlen, P. C. , Zuardy, I. , 2005, “ Sandwich Structures Technology in Commercial Aviation,” Sandwich Structures 7: Advancing with Sandwich Structures and Materials, Thomsen, O., Bozhevolnaya, E., and Lyckegaard, A. eds., Springer, Dordrecht, The Netherlands.
Anders, M. , Zebrine, D. , Centea, T. , and Nutt, S. , 2017, “ In Situ Observations and Pressure Measurements for Autoclave Co-Cure of Honeycomb Core Sandwich Structures,” ASME J. Manuf. Sci. Eng., 139(11), p. 111012. [CrossRef]
Kodiyalam, S. , Nagendra, S. , and DeStefano, J. , 1996, “ Composite Sandwich Structure Optimization With Application to Satellite Components,” AIAA J., 34(3), pp. 614–621. [CrossRef]
Huang, X. , and Xie, Y. M. , 2008, “ Optimal Design of Periodic Structures Using Evolutionary Topology Optimization,” Struct. Multidiscip. Optim., 36(6), pp. 597–606. [CrossRef]
Gibson, L. J. , and Ashby, M. F. , 1999, Cellular Solids: Structure and Properties, Cambridge University Press, Cambridge, UK.
Huang, S. N. , and Alspaugh, D. W. , 1974, “ Minimum Weight Sandwich Beam Design,” AIAA J., 12(12), pp. 1617–1618. [CrossRef]
Li, X. , Li, G. , Wang, C. H. , and You, M. , 2012, “ Optimisation of Composite Sandwich Structures Subjected to Combined Torsion and Bending Stiffness Requirements,” Appl. Compos. Mater., 19(3–4), pp. 689–704. [CrossRef]
Catapano, A. , and Montemurro, M. , 2014, “ A Multi-Scale Approach for the Optimum Design of Sandwich Plates With Honeycomb Core—Part I: Homogenization of Core Properties,” Compos. Struct., 118, pp. 664–676. [CrossRef]
Catapano, A. , and Montemurro, M. , 2014, “ A Multi-Scale Approach for the Optimum Design of Sandwich Plates With Honeycomb Core—Part II: The Optimization Strategy,” Comp. Struct., 118, pp. 677–690. [CrossRef]
Krieglsteiner, J. , Horst, P. , and Schmidt, C. , 2014, “ Characterization of Fiber-Reinforced Stiffener Profiles for Aircraft Fuselage Preliminary Structural Design,” 16th European Conference on Composite Materials (ECCM), Seville, Spain, June 22–26, pp. 1–8.
Tosh, M. W. , and Kelly, D. W. , 2001, “ Fibre Steering for a Composite C-Beam,” Comp. Struct., 53(2), pp. 133–141. [CrossRef]
Alinia, M. M. , and Moosavi, S. H. , 2008, “ A Parametric Study on the Longitudinal Stiffeners of Web Panels,” Thin-Walled Struct., 46(11), pp. 1212–1223 [CrossRef]
Kaufmann, M. , Zenkert, D. , and Mattei, C. , 2008, “ Cost Optimization of Composite Aircraft Structures Including Variable Laminate Qualities,” Comp. Sci. Technol., 68(13), pp. 2748–2754. [CrossRef]
Mukhopadhyay, M. , 2004, Mechanics of Composite Materials and Structures, University Press, Hyderguda, India.
Zenkert, D. , 1995, An Introduction to Sandwich Construction, Engineering Materials Advisory Services, London.
Gutowski, T. G. , 1997, Advanced Composites Manufacturing, Wiley, Cambridge, UK.
Advanced Ceramics Manufacturing, 2017, “ Advanced Ceramics Manufacturing,” Tucson, AZ, accessed June 20, 2017, http://www.acmtucson.com
Black, S. , 2015, “ 3D Printing Moves Into Tooling Components,” CompositesWorld, Cincinnati, OH, accessed June 15, 2017, https://www.compositesworld.com/articles/3d-printing-moves-into-tooling-components
ASTM, 2012, “ Standard Terminology for Additive Manufacturing Technologies,” West Conshohocken, PA, Standard No. ASTM F2792-12a.
Stratasys, 2017, “ Introduction to Additive Manufacturing for Composites,” Stratasys, Eden Prairie, MN, accessed June 20, 2017, http://www.stratasys.com/de/campaign/ebook/additive-manufacturing-for-composites
Li, H. , Taylor, G. , Bheemreddy, V. , Iyibilgin, O. , Leu, M. , and Chandrashekhara, K. , 2015, “ Modeling and Characterization of Fused Deposition Modeling Tooling for Vacuum Assisted Resin Transfer Molding Process,” Addit. Manuf., 7, pp. 64–72. [CrossRef]
Lušic, M. , Schneider, K. , and Hornfeck, R. , 2016, “ A Case Study on the Capability of Rapid Tooling Thermoplastic Laminating Moulds for Manufacturing of CFRP Components in Autoclaves,” Procedia CIRP, 50, pp. 390–395. [CrossRef]
Prüß, H. , and Vietor, T. , 2015, “ Design for Fiber-Reinforced Additive Manufacturing,” ASME J. Mech. Des., 137(11), p. 111409. [CrossRef]
Hassen, A. , Lindahl, J. , Chen, J. , Post, B. , Love, L. , and Kunc, V. , 2016, “ Additive Manufacturing of Composite Tooling Using High Temperature Thermoplastic Materials,” SAMPE Conference Proceedings, Long Beach, CA, May 23–26, pp. 2648–2658.
Stratasys, 2017, “ Sacrificial Tooling and Mandrels Composite Part Fabrication—Design Guide,” Stratasys, Eden Prairie, MN, accessed June 21, 2017, http://www.stratasys.com/solutions/additive-manufacturing/tooling/composite-tooling
Türk, D.-A. , Triebe, L. , and Meboldt, M. , 2016, “ Combining Additive Manufacturing With Advanced Composites for Highly Integrated Robotic Structures,” Procedia CIRP, 50, pp. 402–407. [CrossRef]
Nygaard, J. V. , and Lyckegaard, A. , 2007, “ Sandwich Beam With a Periodical and Graded Core Manufactured Using Rapid Prototyping,” J. Sandwich Struct. Mater., 9(4), pp. 365–376. [CrossRef]
Williams, R. R. , Howard, W. E. , and Martin, S. M. , 2011, “ Composite Sandwich Structures With Rapid Prototyped Cores,” Rapid Prototyping J., 17(2), pp. 92–97. [CrossRef]
Li, T. , and Wang, L. , 2017, “ Bending Behavior of Sandwich Composite Structures With Tunable 3D-Printed Core Materials,” Compos. Struct., 175, pp. 46–57. [CrossRef]
Morena, J. J. , 2011, Mold Fabrications, Wiley Encyclopedia of Composites, Hoboken, NJ.
Bitzer, T. , 2012, Honeycomb Technology: Materials, Design, Manufacturing, Applications and Testing, Springer Science & Business Media, Dordrecht, The Netherlands.
Stankunas, T. , Mazenko, D. , and Jensen, G. , 1989, “ Cocure Investigation of a Honeycomb Reinforced Spacecraft Structure,” 21st International SAMPE Technical Conference, Atlantic City, NJ, pp. 176–188.
Campbell , F. C., Jr. , 2003, Manufacturing Processes for Advanced Composites, Elsevier, Oxford, UK.
ROHACELL, 2017, “ Rohacell IG-F Datasheet,” Essen, Germany, accessed May 8, 2017, http://www.rohacell.com/sites/lists/RE/DocumentsHP/ROHACELL%20IG_IG-F%20Product%20Information.pdf
Sigmund, O. , Aage, N. , and Andreassen, E. , 2016, “ On the (Non-)Optimality of Michell Structures,” Struct. Multidiscip. Optim., 54(2), pp. 361–373. [CrossRef]
Kussmaul, R. , Zogg, M. , and Ermanni, P. , 2018, “ An Optimality Criteria-Based Algorithm for Efficient Design Optimization of Laminated Composites Using Concurrent Resizing and Scaling,” Struct. Multidiscip. Optim. (epub).
Sriapai, T. , Walsri, C. , and Fuenkajorn, K. , 2012, “ Effect of Temperature on Compressive and Tensile Strength of Salt,” ScienceAsia, 38(2), pp. 166–174. [CrossRef]
3D Systems, 2017, “ DuraForm HST Composite Datasheet,” 3D Systems, Rock Hill, SC, accessed May 8, 2017, https://www.3dsystems.com/materials/duraform-hst-composite/tech-specs
Schmid, M. , 2015, Selektives Lasersintern (SLS) Mit Kunststoffen, Hanser, Munich, Germany.
Türk, D. A. , Brenni, F. , Zogg, M. , and Meboldt, M. , 2017, “ Mechanical Characterization of 3D Printed Polymers for Fiber Reinforced Polymers Processing,” Mater. Des., 118, pp. 256–265. [CrossRef]
Gere, J. M. , and Goodno, B. J. , 2013, Mechanics of Materials, Cengage Learning, Stamford, CT.
Dewulf, W. , Pavan, M. , Craeghs, T. , and Kruth, J.-P. , 2016, “ Using X-Ray Computed Tomography to Improve the Porosity Level of Polyamide-12 Laser Sintered Parts,” CIRP Ann., 65(1), pp. 205–208. [CrossRef]
Shaw, B. , and Dirven, S. , 2016, “ Investigation of Porosity and Mechanical Properties of Nylon SLS Structures,” 23rd International Conference on Mechatronics and Machine Vision in Practice (M2VIP), Nanjing, China, Nov. 28–30, pp. 1–6.
Ho, H. C. H. , Gibson, I. , and Cheung, W. L. , 1999, “ Effects of Energy Density on Morphology and Properties of Selective Laser Sintered Polycarbonate,” J. Mater. Process. Technol., 89–90, pp. 204–210. [CrossRef]
Rahman, K. M. , Hu, Z. , and Letcher, T. , 2017, “ In-Plane Stiffness of Additively Manufactured Hierarchical Honeycomb Metamaterials With Defects,” ASME J. Manuf. Sci. Eng., 140(1), p. 011007. [CrossRef]
Beyer, D. , and Figueroa, D. , 2016, “ Design and Analysis of Lattice for Additive Manufacturing,” ASME J. Manuf. Sci. Eng., 138(12), p. 121015.. [CrossRef]
Schmidt, M. , Pohle, D. , and Rechtenwald, T. , 2007, “ Selective Laser Sintering of PEEK,” CIRP Ann. Manuf. Technol., 56(1), pp. 205–208. [CrossRef]
Fish, S. , Booth, J. C. , Kubiak, S. T. , Wroe, W. W. , Bryant, A. D. , Moser, D. R. , and Beaman, J. J. , 2015, “ Design and Subsystem Development of a High Temperature Selective Laser Sintering Machine for Enhanced Process Monitoring and Control,” Addit. Manuf., 5, pp. 60–67. [CrossRef]


Grahic Jump Location
Fig. 1

Schematic processing route for the manufacturing of a hybrid AM-FRP structure using a structural AM core that is over-laminated with FRP and cured

Grahic Jump Location
Fig. 2

Schematic (a) and section view and (b) of telegraphing effect in co-cured honeycombs adapted from Ref. [34,35]

Grahic Jump Location
Fig. 3

Additive manufactured honeycombs with integrated antitelegraphing structure and roof webs for enhanced bonding to the face sheets

Grahic Jump Location
Fig. 7

Design concept for a CFRP hat-stiffener beam with AM honeycomb core

Grahic Jump Location
Fig. 6

Design space (a) and reference hat stiffener consisting of a machined foam core and a CFRP prepreg layup (b)

Grahic Jump Location
Fig. 5

Processing route for the manufacturing of a hybrid AM-FRP structure using a functional hull made with AM, and a temperature-resistant filler material

Grahic Jump Location
Fig. 4

State-of-the art facing–honeycomb interface using a bonding layer with a difficult filler inspection (a), additive design concept and (b) with horizontal bonding surface for co-cured interface and ideally better shear load introduction

Grahic Jump Location
Fig. 8

Relative material density in a longitudinal section of a sandwich core under three-point bending loading. Based on Ref. [38] using a penalty factor p = 1.

Grahic Jump Location
Fig. 9

Design concept for a hat stiffener with CFRP and an AM core using structural lightweight elements

Grahic Jump Location
Fig. 10

Design concept for a CFRP hat-stiffener beam with functional hull made by AM and a temporary filler material

Grahic Jump Location
Fig. 13

Process (a) and three-point bending (b) simulation model

Grahic Jump Location
Fig. 14

Numerical results for (a) reference, (b) honeycomb, (c) truss, and (d) salt core design for relevant load cases. Results show fairly homogenous distributed displacements during processing loading for (b) and (c) and significantly reduced laminate strains and Von Mises stresses for the three-point bending loading in AM core designs.

Grahic Jump Location
Fig. 11

Manufacturing impressions: first the honeycomb (a), truss (b), and salt (c) cores are produced with selective laser sintering. Then, CFRP layup is applied (d), the assembly is vacuum bagged (e) and cured in the autoclave (f).

Grahic Jump Location
Fig. 12

Weight comparison

Grahic Jump Location
Fig. 16

Force–displacement diagram of representative samples

Grahic Jump Location
Fig. 17

Section view of tested hat stiffeners. All specimens failed in or next to the load introduction area (encircled).

Grahic Jump Location
Fig. 18

Comparison of failure load (a) and bending stiffness (b). Percentage values compared to the reference.

Grahic Jump Location
Fig. 15

Three-point bending test setup at EMPA

Grahic Jump Location
Fig. 19

Light-microscope images showing the section view of the truss design (a), a close view of the interface between the laminate (b) and the HST DuraForm composite material and its porosity (c)

Grahic Jump Location
Fig. 20

Comparison of specific stiffness and specific failure load. Percentages compare to reference design.



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In