PSI - Issue 42

T. Vandellos et al. / Procedia Structural Integrity 42 (2022) 50–57

51

C2 - Restricted

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Author name / Structural Integrity Procedia 00 (2019) 000 – 000 This work presents firstly an experimental study and secondly numerical analysis of a four-point bending test to characterize the behavior of a bonded joint between two woven oxide/oxide CMC plates.

Nomenclature CMC Ceramic Matrix Composite ODM Onera Damage Model

2. Experimental study 2.1. Description of the materials, the sample design and the experimental set-up

The analyzed joint consisted of two woven ceramic matrix composite (CMC) substrates bonded with an alumina based bonding ceramic cement. The both substrates, produced by Safran Ceramics, consisted of 8 harness-satin woven preforms of alumina fibers (Nextel ™ 610) consolidated with alumina matrix. The warp/weft ratio was 0.5 and the warp direction of the substrates was aligned with the length of the sample. The behavior of the bonded joint was characterized experimentally with a four-point bending test described in Jacques (2012) and Martin (2014). As illustrated in Fig. 1-a, the lengths of the both substrates were different in order to obtain a singular stress state close to the corner between the CMC and the bond. Thus, a competition between two damage mechanisms could be studied : (i) the delamination between the bond and the CMC and (ii) the substrate failure. In this study, the thickness of the bond was 0.3 mm whereas the thicknesses of the both CMC substrates were 2.75 mm and 1.8 mm. Finally, the length of the larger substrate was 150 mm, the width was 10 mm and the overlap length was 30 mm. As shown in Fig. 1-b, the inner span length and the outer span length were respectively 128 mm and 145 mm. Their diameter was 10 mm.

Fig. 1. (a) Schematic dimensions of the sample; (b) characteristic dimensions of the four-point bending test

2.2. Description of the experimental behavior A monotonic four-point bending test was performed under controlled displacement at 0.1 mm/min under ambient temperature. The Fig. 2-a shows the experimental load/displacement curve. Three phases can be distinguished. Firstly, the load increases linearly with the displacement. Then a non-linearity occurs at 0.5 mm and a second phase appears with a linear relationship between the load and the displacement from 40N to the maximal load. Finally, the load