Thermal residual stress analysis in continuous Al₂O₃ fiber reinforced NiAl composites

Abstract

Thermal residual stresses (TRSs) in continuous Al2O3 fiber reinforced NiAl composites with and without a BN interlayer were studied by using the finite element method (FEM). The FEM model includes the effect of neighboring fibers of the composite. A minimum sample thickness and a minimum size of the surrounding composite have to be exceeded in order to obtain the correct TRS distribution in simulation. It is shown that the TRS, caused by different thermal expansion of fiber and matrix in the NiAl composite, is sufficiently large to cause fiber damage owing to twinning on different rhombohedral planes in the sapphire fiber. The introduction of a BN interlayer or a higher fiber volume fraction (40–60%) essentially reduces the TRS level in the NiAl composite and lessens the fiber damage. The residual stress in the NiAl composites was experimentally measured by nanoindentation. A good agreement between measurements and finite element analysis was achieved.

Investigations on NiAl composites fabricated by matrix coated single crystalline Al2O3-fibers with and without hBN interlayer

“…The thermal axial compressive stress (TACS) in fibers calculated by Ref. [16] is displayed as a function of temperatures (Fig. 13) owing to the dominant effect of TACS on fiber damage observed in the present study.…”

“…Thermal residual stress built up in the NiAl composite during cooling after diffusion bonding was calculated by means of FEM [16]. The thermal axial compressive stress (TACS) in fibers calculated by Ref.…”

“…a single fiber model, have been exceeded in order to obtain the correct TRS distribution. A detailed description about the single fiber model and FEM model as well as the boundary conditions can be found elsewhere [15,16]. Through FEM analysis the TRS distribution in fiber, matrix and interface was calculated.…”