Structural parameters are critical for the final properties of fibrous materials. Three common parameters (i.e., porosity, thickness and average fiber diameter) of each fibrous material are simultaneously determined based on their air penetration behavior. The Ergun-type equation and the Kozeny-type equation, with the help of the optimization method, are applied to conduct the inverse characterization. The prediction performance of the equations is evaluated by comparing the given pressure drop and the values predicted by the Ergun-type and Kozeny-type equations. The inversely determined parameters are compared with the directly measured values. The results show that the Ergun-type equation and the Kozeny-type equation are suitable for various fibrous materials, including conventional nonwoven materials and nanofibrous membranes. The selection criteria of these two equations are provided based on the relation of pressure drop-airflow velocity and the prediction accuracy. The results also suggest that the Ergun-type equation's coefficients and the Blake–Kozeny–Carman constant of the Kozeny-type equation need to be determined for each material. The relative errors for most of the inversely determined parameters are reasonable. The findings indicate that the airflow-based method is feasible for fibrous materials.
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