Residual thermal stress in SiC/(C/C) (C/C: carbon-fiber-reinforced carbon matrix composite) laminates, which are cooled to 273K after interlayer and SiC layer formations on C/C at 1973K, has been analyzed by a finite element method using a plane-strain element model. It was assumed that the interlayer of the laminate has a controlled compositional gradient, and its thickness is twice that of the SiC layer. The analytical model was 10mm square shape with 1.3mm thick. In order to study the effects of thickness of the SiC layer
tSiC and compositional gradient exponent
P of the interlayer on normal residual thermal stress σ
x,
tSiC and
P were varied from 0.00429 to 0.394mm and from 0.1 to 6.5, respectively.
In the laminate without the interlayer, as
tSiC increases σ
x in the SiC layer decreases, finally reaching a constant value of 785MPa at
tSiC above 0.12mm. It is confirmed that inserting the interlayer is an effective way to reduce σ
x in the SiC layer and the greatest reduction of σ
x in the laminate is obtained when
P is 3. In the laminate with the interlayer of
P=3, as
tSiC increases σ
x in the SiC layer and the interlayer also decrease and σ
x in the SiC layer reaches a constant value of 138MPa at
tSiC above 0.2mm. In the above analysis, if a plane-stress element model is used instead of the plane-strain element model, σ
x and displacement decrease by about 32 and 24%, respectively.
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