高性能碳纤维增强复合材料已成为一种重要的航空材料，在复合材料结构服役过程中分层破坏是一种常见的失效模式。针对T800/环氧复合材料不同加载混合比下的分层行为，对具有0°/45°预制分层界面的复合材料层压板分别开展双悬臂梁（DCB）、三点弯（ENF）和混合模式弯曲（MMB）实验，获得复合材料张开型（I型）、滑开型（II型）和I/II混合型分层的断裂韧度，研究其分层扩展行为。结果表明：不同加载混合比（II型分层载荷所占比例）下分层的断裂韧度和分层扩展行为显著不同，加载混合比越大，分层断裂韧度值越高，稳定的分层扩展行为越难保持。基于对实验数据的拟合，建立了一个任意加载混合比下0°/45°分层界面断裂韧度的预测公式。“,”High performance carbon-reinforced composite materials have become important aeronautical materials. During the service time, the delamination fracture of composite structures is a common failure mode. In this study, in order to investigate the delamination behaviours of T800/epoxy composite materials under different mixture ratios, DCB, ENF and MMB tests were conducted on composite laminates with pre-set 0°/45° interface respectively. From the test, the initial delamination fracture toughness and delamination growth behaviour were obtained. The test results show that the fracture toughness and delamination behaviour are significantly affected by the mixture ratio. With the increase of mixture ratio, the fracture toughness increases, and steady delamination growth behaviour is more difficult to maintain. Based on the data fitting method, a prediction function for fracture toughness of the 0°/45° interface at arbitrary mixture ratio is established, which has some engineering values.