CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 41 (2015) 7836–7846 Microstructure and flexural properties of multilayered fiber-reinforced oxide composites fabricated by a novel lamination route Paula O. Guglielmi a,n,1 , Diego Blaese a , Murilo P. Hablitzel b , Gabriel F. Nunes b , Victor R. Lauth b , Dachamir Hotza c , Hazim A. Al-Qureshi b , Rolf Janssen a a Institute of Advanced Ceramics, Hamburg University of Technology (TUHH), Denickestrasse 15, 21073 Hamburg, Germany b Department of Mechanical Engineering, Federal University of Santa Catarina (UFSC), 88040-970 Florianópolis, Brazil c Department of Chemical Engineering, Federal University of Santa Catarina (UFSC), 88040-900 Florianópolis, Brazil Received 30 January 2015; received in revised form 21 February 2015; accepted 21 February 2015 Available online 28 February 2015 Abstract All-oxide ceramic matrix composites produced by a novel route based on the lamination of thermoplastic prepregs are investigated. This route allows for the production of composites with very homogeneous microstructures and a reduced amount of matrix cracks. Nextel TM 610 alumina woven fabric is used here to reinforce a porous oxide matrix composed of 80 vol% Al 2 O 3 and 20 vol% ZrO 2 . The mechanical behavior of composites submitted to different heat treatments is investigated under 4-point bending and short beam shear. Results show that composites with low interlaminar shear strength present a graceful failure under 4-point bending, characterized by a stepwise stress reduction upon straining beyond the peak stress. The fracture of such composites is accompanied by a series of interfacial delamination events, which enhance energy dissipation during failure. An increase of the interlaminar shear strength due to matrix densification causes a loss of the stepped stress–strain behavior. Nevertheless, fiber-related toughening mechanisms such as crack deflection and bridging still ensure inelastic deformation up to failure of these composites. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Ceramic matrix composites; Thermoplastic prepregs; Lamination; Alumina; Zirconia 1. Introduction Continuous fiber-reinforced ceramic matrix composites (CMCs) were developed to overcome the inherent brittleness and conse- quent catastrophic failure of ceramics [1]. The energy released during the failure of CMCs is enhanced by a series of toughening mechanisms such as crack deflection at fiber–matrix interfaces or interphases, crack bridging and fiber pullout, normally leading to a quasi-ductile fracture behavior [1–3]. Among the different classes of CMCs, much attention has been drawn to all-oxide systems because of their chemical stability in oxidizing environments [3,4]. Toughness is typically achieved in these materials by a weak, porous matrix that enables debonding at fiber–matrix interfaces [3,5]. These composites are usually pro- duced by liquid infiltration techniques, in which matrix particles are impregnated into fiber tows, fabrics or preforms via aqueous slurries or sols [3, 6–8]. After drying the liquid carrier, the matrix is sintered at moderate temperatures ( o1300 1C) to avoid strength degradation of the polycrystalline oxide fibers [3,7], as well as to ensure a partial sintering of the matrix, leading to the porosity necessary for damage tolerance [5]. One of the challenges of this process is the consolidation of flawless matrices, since the const- rained shrinkage imposed by the rigid network of fibers causes the formation of matrix cracks during drying and sintering [1,3,6]. These flaws may not just be detrimental to the mechanical pro- perties of the composites [8–10], but also compromise their ther- mal shock resistance by decreasing the thermal conductivity of the material [11,12]. www.elsevier.com/locate/ceramint http://dx.doi.org/10.1016/j.ceramint.2015.02.120 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. n Corresponding author. Tel.: þ 49 0 41 5287 2631; fax.: þ49 0 41 5287 2625. E-mail address: paula.guglielmi@hzg.de (P.O. Guglielmi). 1 Current address: Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, Max-Planck-Strasse 1, 21502 Geesthacht, Germany.