Material Modelling of Fabric Deformation in Forming Simulation of Fiber-Metal Laminates – A Review on Modelling Fabric Coupling Mechanisms

Abstract

During forming of complex fiber-metal laminates (FML), compressive stress zones occur. In pure textile forming, these compressive stresses typically lead to extensive wrinkling. In FML forming, however, wrinkling is partly hindered by the metal layers. Thus, combined stress states occur, where compression influences the deformation. In forming simulation, these compressive stresses can lead to erroneous formation of shear bands within the fabric layer, if the deformation behavior is not modelled correctly. Simple fabric models neither consider interactions between roving directions nor model interactions between membrane strains and shear strains. More advanced invariant-based hyperelastic material models are able to capture these interactions, but only consider tension and shear, while disregarding compression. A common assumption is to set the fabric compression stiffness close to zero. Experimentally, the in-plane fabric compression stiffness has not been determined so far. However, in FML forming, the compression stiffness and the combined compression-tension-shear behavior becomes relevant. In this article, the authors summarize and analyze the capacity of state-of-the-art fabric material models to predict the deformation behavior of fabrics under combined loading. Based on these findings, conclusions are drawn for a new macroscopic modeling approach for woven fabrics, including coupling of tension, compression and shear.

Modeling multiaxial stress states in forming simulation of woven fabrics

“…Since experimental studies have shown interdependencies between distinct strain components, hyperelastic models with invariant-coupling, e.g., biaxial-tension [18] and tension-shear coupling [19], have been proposed. A recent review on modelling coupling mechanisms in woven fabrics, with particular focus on invariant-based constitutive modeling is given in [20].…”

Robotic-Assisted Measurement of Fabrics for the Characterization of the Shear Tension Coupling

“…Based on this theory, many researchers [2,15,23,26], have developed hyperelastic constitutive models to investigate the mechanical behaviour of dry fabrics under large deformations. Indeed, the non-linear macroscopic material behavior has to be set in the constitutive equations [17]. It is also worth noting that in the framework of in-plane shear tests, two major methods have been proposed and studied i.e Picture Frame Test and Bias Extension Test.…”

“…This mechanical property would normally lead to the formation of wrinkles as discussed in [16]. Werner et al [17], in their review on the modeling of fabric coupling mechanisms commented on the shear stress characteristic during angular variation of the rovings. Immediately the yarns come into contact with each other, the shear force increases, which is definitely attributed to the lateral compaction of rovings.…”

“…From their work, it is indeed evident that strain in one fiber direction induces both longitudinal normal stresses and stresses in transverse directions. According to [17], the crimping in the rovings is reduced along the loaded direction. As this happens waviness of the unloaded yarn direction increases leading to the effect referred to as "crimp interchange".…”

“…As this happens waviness of the unloaded yarn direction increases leading to the effect referred to as "crimp interchange". As this stage fades away due to further loading, yarns are stretched, which is then impacted by the high tensile stiffness that brings about a sharp increase in tensile stresses with increasing longitudinal strain [17,19,20,21]. These very critical and complex mechanical properties have been studied independently while neglecting their coexistence and interaction.…”