Low-cost and reliable production of oxide ceramic matrix composites

• Applicant: Dr.-Ing. Rolf Janssen
• Subject Area: Glass, Ceramics and Derived Composites
• Term: from 2009 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 138847206

• Final Report Year: 2015

Final Report Abstract

Multilayered fiber-reinforced oxide composites fabricated by the prepreg technology developed in this project combine fracture mechanisms from both layered ceramics and fiber reinforced CMCs. The ability of carrying reduced loads after the first failure was present in all composites analyzed. In case of respective microstructural tailoring, a high maximum flexural strength is achieved followed by a sawlike stress reduction upon further straining. The essential aspects are: • A new route based on the lamination of thermoplastic prepregs was developed and successfully applied to produce multilayered fiber-reinforced oxide composites. A great advantage of this route is the possibility it offers for shaping and joining different CMC parts in the green state, due to the thermoplastic behavior of the prepregs used. Microstructural analysis proved the effective joining of the different prepreg layers during the consolidation of the composites. The new route is used at present in a German Research project supported in the ZIM frame, e.g. in collaboration with industrial partners. The aim is to manufacture a complex shaped CMC–rotor for service in harsh envirionments. • The best mechanical properties were observed in the composite prepared using alumina and zirconia powder for the matrix and sintering at 1200°C, .e.g. a high nominal strength was achieved followed by a stepped stress-strain behavior, similar to that of high toughness multilayered ceramics. • Slight derivations from the optimal microstructure, for example by sintering at 1300 °C or sintering at 1200 °C in combination with an annealing at 1100 °C, reduced the gracefull failure features to some extent. However, toughening mechanisms related to the fiber reinforcement, such as crack deflection at fiber-matrix interfaces, were still present in these samples, which lead to a slight non-linear stress-strain behavior up to failure, as well as a much larger strain at fracture when compared to monolithic ceramics. Observation of crack deflection was consistent to predictions according to the He and Hutchinson model for all samples. • The new routes is based on a two step infiltration. Thereby, the properties of the intrabundle and intertextile matrix can be designed independently. In this project, we´ve used a slightly lower matrix density in the bundle (obtained by the slurry infiltration of the textile) compared to the matrix between the textile layers (realized by the wax based suspension). This feature is a unique option of the process and can be used even to design more complex structures – for example different phases are possible for the intrabundle and intertextile maxtrix. Thereby, the load transfer in the bundle could be optimized – a feature non yet investigated by anyone. It is intended to start a new research project on this option in a collaboration with DLR Stuttgart and University Bayreuth. • Beside tailoring the intrabundle and intertextile matrix independently, the prepreg roures offers also the option to stack layers of different composition or structure creating thereby a fiber reinforced functional graded materials (Fiber-FGM). Thereby, also the surface performance can be altered in order to enhance wear or corrosion resistance – an option at present under development in the collaborative ZIM project mentioned above.

Publications

• A Prepreg Approach for Low Cost Oxide-Oxide Composites, in “High Temperature Ceramic Materials and Composites”, ed. by W. Krenkel & J. Lamon, 420-428 (2010)
  P.O. Guglielmi, R. Janssen, G.F. Nunes, D. Hotza
  
• Reaction Formed Alumina-Alumina FRCMC, in “High Temperature Ceramic Materials and Composites”, ed. by W. Krenkel & J. Lamon , 398-404 (2010)
  R. Janssen
  
• Building a sintering front through fast firing, International Journal of Applied Ceramic Technology ([6] 1486-1493 (2011)
  D.E. Garcia, D. Hotza, R. Janssen
  
• Fiber-Matrix Compatibility in an All-Oxide Ceramic Composite with RBAO Matrix, J. Am. Ceram. Soc. 95 [1], 159-164 (2012)
  S.M.Goushegir, P.O. Guglielmi, J.P.G. Silva, M Hablitzel, D Hotza, H.A. Al-Qureshi, R. Janssen
  
• Mechanical tests and simulation on load sharing in alumina fiber bundles. Ceram. Int. 41 13257-13263 (2015)
  L. Neckel, J.G.P. da Silva, P.O. Guglielmi, D. Hotza, H.A. Al-Qureshi, O.R.K. Montedo, C.P. Bergmann, R. Janssen
  
• Microstructure and Flexural Properties of Multilayered Fiber-Reinforced Oxide Composites fabrciated by a Novel Lamination Route, Ceramics Int 41 7836-7846 (2015)
  P.O. Guglielmi, D, Blaese, M.P. Hablitzel, G. Nunes, D. Hotza, H.A. Al-Qureshi, R. Janssen
  
• ZrO2 Fiber-Matrix Interfaces in Alumina Fiber-Reinforced Model Composites, J. Eur. Ceram. Soc. 35 (2015) 1593-1598
  D. Blaese, D:E. Garcia, P. Guglielmi, D. Hotza, M. C. Fredel, R. Janssen
  
• Processing of All-Oxide Ceramic Matrix Composites with RBAO Matrices, J. Ceram. Sci. Tech. 7 [01] 87-96, 2016
  P.O. Guglielmi, D.E. Garcia, M.P. Hablitzel, D. Blaese, D.P. Goulart, A. Borchert, D. Hotza, R. Janssen