After briefly reviewing the proceeding of geometric model of 4-step 3-D (1×1) rectangular braided composites, yarn path in 4-step rectangular braiding process is analyzed. On this basis, a 3-D solid unit cell geometric model is proposed, the characteristics of geometry of 3-D braided composites are studied and yarn-jamming condition is discussed. Compared with conventional geometric models, the identified geometric model reflects the continuity of yarn in 3-D braided composites, which makes each unit cell assembled reasonably, so the structural integrity of 3-D braided composites is assured. The 3-D solid geometric model makes it possible to correctly consider the interactions between yarn and matrix for analysis of effective mechanic behaviors of 3-D braided composites.
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