Fabric bending stiffness

When characterizing the dry fabric bending stiffness, a cantilever beam method is often used (de Bilbao et al., 2009), where the fabric is allowed to... 

Finite element models similar to the experimental fabric samples are used to determine the fabric bending stiffness. Equivalent tip displacements are prescribed in the models and a range of bending-stiffness values are used to replicate the experimental profile shape of the sample. While several values... 

Solid PET polymer is relatively hard and brittle. It must be formed into very fine fibers in order to exhibit a bending stiffness that is low enough for textile materials. Most commercial PET fibers are produced in a diameter range of about 10-50 pm, considerably smaller than a human hair. Within this range lie large differences in the softness, drape and feel of fabrics formed from the fibers, since the bending stiffness of a cylindrical fiber depends on the 4th power of its diameter. 

Bending length n. A measure of fabric stiffness based on how the fabric bends in one plane under the force of gravity. Paint/ coatings dictionary. Federation of Societies for Coatings Technology, Philadelphia, Blue Bell, PA, 1978. 

This property governs the handling, comfort and conformabUity of a fabric and is a critical parameter in many applications of textiles in medicine, such as sutures, arterial grafts, ligaments, tendons, heart valve leaflets, etc. Bending stiffness is given by ... 

As mentioned previously, the formation of wrinkles and/or waves depends on the combination of in-plane shear, tension and bending behaviors of the fabric. It is certainly possible to predict defects based on the in-plane shear and tension behaviors alone. However, the bending stiffness more accurately defines the wrinkle/wave shape. For example, compressing a fabric sample model from two sides will yield a different number of out-of-plane waves with different amplitudes depending on the magnitude of the bending stiffness. A much stiffer fabric will result in fewer waves with greater... 

FE model of a fabric sample compressed from each side with (a) high bending stiffness and with (b) low bending stiffness. 

To bend a fabric, composite, or any fiber-containing products, the bending of fibers is required. In each case, the arrangement of fibers is important in determining the bending stiffness of the final product. However, to understand the bending of the final products, the bending properties of fibers must be studied first. 

Years of development have led to a standardized system for objective evaluation of fabric hand (129). This, the Kawabata evaluation system (KES), consists of four basic testing machines a tensile and shear tester, a bending tester, a compression tester, and a surface tester for measuring friction and surface roughness. To complete the evaluation, fabric weight and thickness are determined. The measurements result in 16 different hand parameters or characteristic values, which have been correlated to appraisals of fabric hand by panels of experts (121). Translation formulas have also been developed based on required levels of each hand property for specific end uses (129). The properties include stiffness, smoothness, and fullness levels as well as the total hand value. In more recent years, abundant research has been documented concerning hand assessment (130—133). 

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