A semi-analytical model of size effect of interlaminar mechanical properties of woven ceramic composites based on the statistical damage

In this work, the size effect on the interlaminar mechanical properties of laminated fiber-reinforced ceramic composites (CMCs) was described by a novel semi-analytical theoretical framework. This theory integrates the Weibull statistical model, which governs the damage evolution in brittle matrix materials, with an analytical expression for the interlaminar mechanical properties. The interlaminar performance is characterized by a dimensionless quantity that captures the competition between interlaminar crack propagation and bending failure during the fracture process. The effective damage factor observed on the fracture surface serves as the key link combining these components. To accurately represent the woven architecture of CMCs, the variables in the size-effect theory were defined using a dimensionless parameter: the ratio of the unit cell size of the weave pattern to the specimen dimension. Consequently, the resulting model inherently reflects material-specific characteristics. To validate the theory, wedge-loaded double cantilever beam (W-DCB) tests were performed on CMC specimens with varying widths. The experimental results confirmed that the interlaminar mechanical properties—including the trans-thickness strength (TTS), the mode I interlaminar fracture toughness (G_Ic), and the damage area—exhibit a discernible size effect. Apparent observations of the fracture surfaces revealed variations in the damaged area with changing specimen size. The proposed model's validity and accuracy were corroborated by measuring the effective damage factor across different specimen sizes and comparing these measurements with predictions from the derived size-effect relationship.