Tailoring structural and mechanical properties of Cf/SiC ceramic matrix composites with BN/SiAlC interphases
In this work, we studied the effects of protective boron nitride/silconaluminocarbide (BN/SiAlC) interphases on the structural and mechanical properties of fabricated stacked carbon fiber-reinforced SiC ceramic matrix composites (C f /SiC CMCs) via the hot-press sintering route. The structural analyses were carried out by X-ray diffraction and scanning electron microscopy (SEM), while mechanical properties were elucidated by employing universal testing machine. The observed sharp diffraction peaks indicate excellent crystallization, and the formation of 4 H -SiC polytype was attributed to the partial transition of β -SiC phase during high-temperature sintering. The composite with single BN interface layer revealed enhanced bending strength of up to 364 ± 39.46 MPa (↑40 %), while composite with double layered interface showed optimal strength of 436 ± 33.54 MPa, and toughness of 6.11 ± 0.74 MPa m 1/2 , with increments of 67.7 % and 128.8 %, respectively, compared to the composite without interphase layer. In the composite with duplex interfacial layer (3BN/SiAlC), the microcracks generated during fracture propagated into the BN layer, deflected through both the sublayers and at the fiber-BN interface, resulting in fiber pull out using fracture energy, leading to the enhanced strength and toughness of the composite. The load-displacement curve revealed that the stacking C f /SiC CMCs with weak interlayer binding owing to the BN/SiAlC coating treatment possesses significant toughness to the SiC ceramics.
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