Abstract
The fracture behavior of TRISO-coated fuel particles depends significantly on the shear strength at the interface between the inner pyrolytic carbon (PyC) and silicon carbide (SiC) coatings. In this study, a micro-indentation fiber push-out test was applied to evaluate the interfacial shear properties of a model TRISO-coated tube. Specifically, a non-linear shear-lag model for a transversely isotropic composite material was developed because the existing isotropic models often overestimate the results. In the model, the effects of thermal residual stresses and the roughness-induced clamping stress were considered because of a particular importance. The rigorous model proposed in this study provides more reasonable data on two important interfacial shear parameters: an interfacial debond shear strength and an interfacial friction stress. The modified model gives the interfacial debond shear strength of 180 � 40 MPa. Such an unusually high interfacial strength, even though the value was comparably lower than that obtained by the existing isotropic model (~280 MPa), could allow significant loads to be transferred between the inner PyC and SiC in application, potentially leading to failure of the SiC layer. On the other hand, the interfacial friction stress of 120 � 30 MPa was measured. The considerably high friction stress is attributed primarily to the roughness at the cracked interface rather than the thermal effect. PACS: 68.35.Ct; 68.35.Gy; 81.05.Je; 81.70.Bt
