PSI - Issue 42

T. Vandellos et al. / Procedia Structural Integrity 42 (2022) 50–57 C2 - Restricted Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3 strongly decreases until the end of the test. The Fig. 2-b and Fig. 2-c illustrate the failure of the larger woven CMC substrate, close to the corner of the bonded joint. This failure explains the third phase of the experimental curve.

Fig. 2. (a) Experimental load/displacement curve ; (b-c) photos of the broken sample

In order to understand (i) the non-linearity appearing between the first and the second phases and (ii) the reason why the failure of the substrate occurs before the delamination between the bond and the CMC material, numerical analysis with three kinds of model were performed. The next sections describe and discuss the numerical results. 3. Numerical analysis 3.1. Description of the finite element models The Fig. 3 shows the boundary conditions of the two-dimensional plane-stress model built with an implicit commercial finite element code. The inner rollers were clamped whereas the outer rollers, associated with a reference point RP-1 , moved only in the y direction under controlled displacement ( i.e. displacement in the x direction was null). The reaction force, used for the numerical load/displacement curves, was calculated at the reference-point. The mesh consisted of quadratic hexahedral elements with a very fine mesh in the corner between the CMC and the bond as shown in Fig. 4. The bond and the CMC substrates have the same mesh discretization at the interfaces. To model the possible delamination between the longer CMC substrate and the bond, zero-thickness cohesive elements were inserted. Concerning the rollers, linear tetrahedral elements were used. Contacts between CMC substrates and metallic rollers were defined with frictionless general contact properties.

Fig. 3. Boundary conditions