Abstract: Delamination damage is one of the primary damage modes in aerospace composite structures. Mode I delamination exhibits characteristics of low initial fracture toughness and complex damage patterns. Analyzing the interrelationships among three damage mechanisms at the crack tip region and bridging fiber damage evolution plays a crucial role in studying Mode I delamination. This paper specifically designs T700 level carbon fiber/epoxy composite laminates with three different interlayer configurations (0//0, 0//45, 0//90) and conducts Mode I delamination tests. By observing the initiation and evolution of delamination, summarizing double cantilever beam (DCB) experimental results in load-displacement curves and R-curves, and employing various characterization methods like SEM analysis based on specimen fracture surfaces, it reveals the damage mechanisms at the crack tip. Subsequently, a new approach to decoupling layered damage mechanisms is proposed, based on three bilinear cohesive constitutive laws. This method establishes a cohesive element model to decouple layered damage mechanisms at different damage scales, independently characterizing the contributions of different damage mechanisms during layered propagation. Parameters required for simulation are obtained from experiments, and the simulated results exhibit good consistency with experimental data.