Fabric Stiffness Testing

Fabric stiffness testing mainly conducts scientific testing and analysis on stiffness determination by the cantilever method, stiffness determination by the inclined plane method, stiffness determination by the heart loop method, dynamic stiffness testing and multi-directional bending stiffness analysis, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Stiffness determination by the cantilever method: This method is mainly used to evaluate the drape performance and flexural rigidity of the fabric. By measuring the overhang length or bending angle of the fabric specimen under its own weight, its bending length and flexural rigidity are calculated. It is the basic item for evaluating the degree of "crispness" of the fabric hand feel. This item is especially important for evaluating garment fabrics such as suits and coats that need to maintain their shape.

Stiffness determination by the inclined plane method: This method simulates the bending behavior of the fabric on an inclined plane, and characterizes its stiffness by measuring the length of the specimen sliding or bending on a specific inclined plane. The test process is intuitive and the results are highly repeatable, and it is often used for rapid evaluation and comparison of different fabrics, especially the crispness of woven fabrics and nonwovens.

Stiffness determination by the heart loop method: In this item, the fabric specimen is folded into a heart shape, and the drooping distance of its top under its own weight is measured. The smaller the drooping distance, the stiffer the fabric. This method is simple to operate, is suitable for the preliminary hand feel evaluation of light and thin fabrics and textiles, and is widely used in production and quality control.

Dynamic stiffness testing: Different from the static bending test, in this item, under the conditions of periodic bending load on the fabric, its bending modulus and hysteresis loss are measured. The dynamic stiffness can better reflect the crispness retention ability and fatigue characteristics of the fabric during actual wearing and movement, and is of great significance for the evaluation of sportswear and functional fabrics.

Multi-directional bending stiffness analysis: The stiffness of the fabric in the warp, weft and bias directions may differ significantly. In this item, the bending properties of the fabric in different directions need to be tested separately, to comprehensively evaluate its anisotropy, which has key guiding value for garment cutting, sewing processes and the shape fitting of the final product.

Testing Scope

Woven fabrics and knitted fabrics: Including plain, twill and satin woven fabrics made of cotton, linen, wool, silk and various chemical fibres, as well as weft-knitted and warp-knitted fabrics. Different structural organizations directly affect the bending rigidity of the fabric, and testing needs to cover its stiffness characteristics in the warp and weft directions and the longitudinal and transverse directions of the loops.

Nonwovens and industrial textiles: Covering nonwovens produced by processes such as spunlace, needle-punching, thermal bonding and chemical bonding, as well as coated fabrics, laminated composites, geotextiles and filter materials. These materials have a wide stiffness range, and testing is crucial for their processing suitability (such as molding) and final use performance.

Garments and home textiles: For garment fabrics requiring specific silhouettes such as shirts, suits, dresses and trousers, as well as home textiles such as curtains, tablecloths and bedspreads. The purpose of testing is to ensure that the fabric has the crispness, drape and shape retention ability that meet the design requirements.

Coated and finished fabrics: Including fabrics treated with resin finishing, stiffening finishing, coating (such as PVC and PU) and lamination. The finishing process significantly changes the hardness of the fabric, and testing is used to evaluate the uniformity, durability and compliance with product specification requirements of the finishing effect.

Special functional and intelligent textiles: Involving high-strength and high-modulus fibre fabrics in bulletproof vests and safety protective clothing, as well as intelligent textiles such as memory-type and phase-change types. Stiffness testing is an important part of their mechanical property evaluation system, and is related to the protective efficiency and intelligent response characteristics of the products.

Testing Methods

ASTM D1388 cantilever method: This is one of the most widely used standard methods. A rectangular fabric strip is placed on a horizontal platform and slowly pushed out of the platform edge until its front end droops down to touch the inclined plane due to its own weight. The pushed-out length (bending length) is measured, and the bending length and flexural rigidity are calculated from it. The method is classic and the data are highly comparable.

ISO 9073-7 nonwoven drape method: A stiffness test method specifically formulated by the International Organization for Standardization for nonwovens. The principle is similar to the cantilever method, but the specific specimen size, test conditions and calculation formula are adjusted according to the characteristics of nonwovens, to ensure the accuracy and representativeness of the test results.

GB/T 18318.1 fabric stiffness test Part 1: inclined plane method: A Chinese national standard method. It specifies the use of a fixed 45° inclined plane, and measures the length of the fabric strip bending and sliding down the inclined plane due to its own weight. This method has simple equipment and fast operation, and is especially suitable for rapid inspection and quality control at the production site.

JIS L1096 heart loop method: A method specified by the Japanese Industrial Standard. The fabric specimen is cut to a specific size, folded in half and sewn into a heart shape, and after hanging, the vertical distance of the droop of its top is measured. This method has high requirements for specimen preparation, but can comprehensively reflect the bending and shearing properties of the fabric, and is often used to evaluate the "body" of the fabric.

KES-FB2 pure bending test: A method in the Kawabata Evaluation System (KES), belonging to high-end precision testing. It can carry out forward and reverse bending of the fabric within a set curvature range, precisely measure its bending moment and hysteresis moment, and thus obtain the bending rigidity (B value) and hysteresis (2HB value), comprehensively characterizing the bending mechanical behavior of the fabric.

Testing Standards

Domestic Standards:

1. GB/T 18318.1-2009, Textiles — Determination of stiffness — Part 1: Inclined plane method

2. GB/T 18318.2-2009, Textiles — Determination of stiffness — Part 2: Cantilever method

3. GB/T 18318.3-2009, Textiles — Determination of stiffness — Part 3: Heart loop method

4. GB/T 18318.4-2009, Textiles — Determination of stiffness — Part 4: Dynamic stiffness method

5. GB/T 6529-2008, Textiles — Standard atmospheres for conditioning and testing

International Standards:

1. ASTM D1388, Standard test method for stiffness of fabrics

2. ISO 9073-7, Textiles — Test methods for nonwovens — Part 7: Determination of bending length

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Digital fabric stiffness tester: The mainstream modern equipment, integrating a precision guide rail, photoelectric sensors or laser displacement sensors and a microprocessor. It automatically completes specimen pushing, bending end point detection, length measurement and data calculation, directly displays and outputs results such as the bending length and flexural rigidity, with high testing efficiency and precision, and complies with standards such as ASTM D1388.

Inclined plane stiffness tester: The structure is relatively simple, with the core components being a smooth metal inclined plane with an angle of precisely 45° and a horizontal platform with a scale. During the test, the specimen is manually pushed across the intersection line of the platform and the inclined plane, and the sliding length of its front end on the inclined plane is read by visual inspection. The equipment has low cost and is easy to maintain.

Fabric style tester (such as the KES-F system): A multifunctional comprehensive testing system, whose bending test unit (FB2) can carry out high-precision pure bending tests. Through precision torque sensors and curvature control mechanisms, a complete bending hysteresis curve is obtained, providing detailed data for in-depth research on the hand feel style and mechanical properties of the fabric.

Nonwoven stiffness tester: Specially designed to meet standards such as ISO 9073-7, and may be equipped with a wider specimen clamping device and test parameter settings adapted to the characteristics of nonwovens, ensuring stable and reliable test results when testing bulky, thick or low-strength nonwoven materials.

Laboratory environmental control system: Not a direct testing instrument, but crucial to the accuracy of the results. It includes constant temperature and humidity chambers and standard atmospheric conditioning balance devices (such as the provisions of GB/T 6529: temperature 20±2 ℃ and relative humidity 65±4%). All fabric specimens must be fully balanced under standard atmospheric conditions before testing, to eliminate the influence of environmental humidity on the rigidity of the fibres.