ABSTRACT
To determine Young’s modulus of the coating without residual stresses within a bi-layer system, Roche and colleagues [1 5 , 16] used a three-point flexure test with a beam theory approach. However, when an interphase layer is created between the coating and the substrate, the bi-layer model is no longer valid. A model that takes into account both the mechanical and geometrical properties of the three layers (coating, interphase and substrate) has to be used. For a three-layered system, Benabdi proposed a model satisfying the interphase formation [8 ]:
where: 7S is the inertia moment of the substrate (7S = bsh3s/ 1 2 ), 7j is the inertia moment of the interphase (7j = b\h]/\2), 7bc is the inertia moment of the coating (7 bc = bbchlc/ 12), bs is the width of the substrate, b\ is the width of the interphase, Z?bc is the width of the bulk coating,
with:
