Accounting for roving slippage in the macroscopic forming simulation of unidirectional non-crimp fabrics

Unidirectional non-crimp fabrics (UD-NCF) are prone to roving slippage during the forming process. While the slippage can facilitate specific forming deformations, it is not captured by conventional macroscopic forming simulation models. This work presents a gradient-enhanced hyperelastic membrane model for UD-NCF that incorporates non-local effects by coupling the transverse tensile response to the local shear angle gradient. Spatial gradients are reconstructed using a weighted least-squares scheme over node-neighbor stencils, and made available inside a standard explicit finite element workflow via a Neighboring Element Method (NEM) implemented in Abaqus/Explicit . The NEM controls global connectivity, nodal data access, and subroutine execution, enabling gradient computation. The model reduces transverse stiffness as a function of the gradient magnitude through a cubic Hermite coupling function, providing a surrogate for smooth and irreversible mesoscopic roving slippage at the continuum scale. Parameterization is carried out using experimental off-axis tension tests at 45 ∘ , and the model is assessed against experiments for 30 ∘ and 60 ∘ . The non-local approach reproduces the characteristic strain localization in transition zones and the reduced strains in the central region, improving agreement with measured strain and shear angle distributions compared to a purely local membrane formulation.