Anisotropic Elastic-Plastic Mechanical Properties of Thermally Bonded Bicomponent Fibre Nonwovens

Having a unique structure, nonwoven fabrics possess distinct mechanical properties dissimilar to those of woven fabrics and composites. Anisotropic elastic-plastic mechanical properties of core/sheath type thermally bonded bicomponent fibre nonwoven textiles are computed based on manufacturing parameters and fibre properties. Initially, tensile tests are performed on nonwoven fabrics and their single fibres to assess their mechanical behaviour and obtain input parameters for the developed algorithms. Random orientation of individual fibres is introduced into the model in terms of the orientation distribution function (ODF). An algorithm, based on the Hough transform, is developed to determine the ODF and calculate the structure’s anisotropy. The nonwoven fabric is modelled as an assembly of two regions — bond points and a fibre matrix, having distinct mechanical properties. Bond points are treated as a deformable bicomponent composite material composed of the sheath material of fibres as matrix reinforced with the core material as fibres with random orientation of reinforcement. On the other hand, the fibre matrix is treated as a composite membrane structure having low stiffness in thickness direction. A second algorithm is developed to calculate anisotropic material properties of these regions based on fibre characteristics and manufacturing parameters; it can be used in numerical modelling as well as product development and optimization of nonwovens.