Abstract: Cold expansion technology is a technique widely used to improve the fatigue life of aerostructures. For composite open-hole structures, the grommet can be expanded into the hole to effectively improve the fatigue life of the laminate. Based on the FEA software ABAQUS, this paper simulates the process flow of grommet hole reinforcement technology of composite laminate, predicts the fatigue life of the laminate after hole reinforcement, and studies the influence of different degrees of cold expansion (DCE) on the fatigue life of the laminate. The results show that: grommet hole reinforcement can generate a certain residual stress field on the hole edge of the laminate and the grommet. There are certain differences in the residual stress field of each layer, and the compressive residual stress on the extrusion outlet surface of the grommet is the highest; there is an optimal DCE , under which the reinforcement will not damage the laminate, and can also generate a suitable residual stress field in the structure, which can maximize the fatigue life of the laminate. The optimal DCE is 2% for the research object in this paper; if the DCE is too large, the grommet hole reinforcement will cause damage at the edge of the hole, mainly the matrix compression damage, which will affect or even reduce the fatigue life of the laminate.

Key words: composites, grommet hole reinforcement, fatigue life prediction