Aramid fiber reinforced plastic (AFRP) composites have been widely used in aerospace, military, and automotive industries. The common drilling process deployed for AFRP manufacturing can induce delamination that drastically deteriorate the mechanical performance and fatigue lives of the drilled AFRP components, therefore, establishing an accurate delamination model is desirable for delamination suppression and hole quality optimization. However, existing delamination models sum up all loads of the chisel edge and cutting lips act on the uncut plies under the chisel edge algebraically, which does not represent the true contact conditions. In this study, a new delamination regime is proposed where delamination caused by thrust forces exerted by both the chisel edge and cutting lips have been considered. On this basis, a novel analytical model in the context of AFRP drilling is proposed for the critical thrust force (CTF) prediction. Double cantilever beam (DCB) and delamination tests have been performed to validate the new model and results show that our proposed model agrees highly with the experimental results where the thrust force exerted by the chisel edge accounts for 24% of the total load during drilling of AFRP.