Non-linear inelastic 3-phase FE Models for Calendered Nonwovens

Nonwovens build a unique class of engineered fabric materials, allowing for a broad range of properties like softness, strength, flame retardancy, washability, cushioning and filtering and many more. Alone in Europe, nonwoven production has passed 3 million tons per year for quite some time now, with the hygiene sector forming the largest market segment.

In view of efficient product design processes, it is important to understand and decently model the true material structure to capture its effects on the deformation behavior at microscopic and macroscopic scales. For material modelers, calendered nonwovens pose some particular challenges in this regard, since not only the fiber properties and the lay down, but also the parameters of the calendering process itself are decisive for the nonwoven performance.

Based on µCT data of real specimens, we propose a three-phase FE-modelling approach based on GeoDICT and Abaqus, which combines well-known beam element representations for the fibers, separate volume discretized models for the bond points and particular connector elements for the interphases surrounding the bond points. Inside these interphases, the low-density fiber regions attach to the much thinner bond points, implying extreme property gradients determined by the calendering process parameters and crucial for the mechanical performance. When the constitutive descriptions for all three components - fibers, bond points and interphases - are calibrated precisely and treated sufficiently complex in view of the relevant inelasticities, such FE-models will enable a completely new level of understanding the structure-property relationships of nonwovens.