Objective To investigate the plastic deformation characteristics at the crack tip and the associated toughening mechanisms in Bouligand structures. Methods A finite element model of a single-edge notched laminated structure was established to compare single-twisted Bouligand structures and double-twisted Bouligand structures. The effects of fiber pitch angle, interfacial strength, and interfacial toughness on the evolution of the crack-tip plastic zone and interfacial damage were systematically analyzed. In addition, a void was introduced into the model to explore its toughening effect. Results The fiber arrangement significantly influences the distribution of the crack-tip plastic zone. The SBS configuration produces a continuous helicoidal plastic zone, whereas the DBS configuration results in a more uniform and larger plastic zone. Increasing interfacial strength suppresses interfacial delamination and significantly enlarges the plastic zone, while interfacial toughness has a limited effect on plastic zone evolution. When a void is introduced, a ligament forms between the crack tip and the void, delaying necking. The Bouligand structure exhibits a higher peak plastic strain and a slower void growth rate, thereby enhancing energy dissipation capacity. Conclusions The evolution of the crack-tip plastic zone in Bouligand structures is jointly governed by fiber architecture and interfacial fracture properties. Void-induced necking further enhances energy dissipation, thereby improving the fracture resistance of the structure. This study provides theoretical guidance for the structural optimization of bioinspired composites with high damage tolerance.