Fiber-level modeling of layer-to-layer interlocked honeycomb preforms

The mechanical properties of composite honeycomb cores are determined by their fiber architecture, yet honeycomb fiber architectures are always highly complex. This paper proposes a fiber-level modeling approach for honeycomb core preforms. Virtual fibers are employed to construct yarn geometries, and the spatial paths of yarns within the honeycomb fabric are generated based on the actual interlacing process. The closed-core to expanded-core conversion process is simulated, and the microstructural variations of the fabric is characterized. The influence of the number of virtual fibers per yarn (n_y) and the length of virtual fiber elements (L_e) on the modeling results is investigated. Models with different parameters were constructed, and the extracted feature parameters were compared with CT slices. The computational efficiency was evaluated based on simulation accuracy and computation time, leading to the identification of n_y = 52 and L_e = 0.2 mm as the optimal modeling parameter. The geometric morphology and internal microstructure characteristics of the honeycomb preform model are highly consistent with the Micro-CT scanning results of the actual sample, with coefficients of variation below 10.00 % for all key microstructural parameters (bonded wall thickness (T_BW): 6.05 %, free wall thickness (T_FW): 6.25 %, bonded wall length (L_BW): 8.42 %, and cavity area (A_C): 8.52 %). Influence of weaving parameters on structure parameters of the honeycomb preform is then investigated. Increasing the weft density from 6 to 10 picks/cm, the average values of T_BW, T_FW and L_BW increase by 3.37 %, 12.90 % and 17.09 % respectively, while the A_C decreases by 25.81 %. This study's modeling method contributes to researching the internal structures of honeycomb preforms and serves as a valuable foundation for mechanical property analysis of composite honeycomb cores.