A Novel Approach for Measurement of Fiber-on-fiber Friction

National Textile Center

Year 8 Proposal

Project No.: F98-S09

Competency:

A Novel Approach for Measurement of Fiber-on-fiber Friction

Project Team:

Leader Yiping Qiu Expertise Fiber Science

Email: yqiu@tx.ncsu.edu Phone: (919) 515-9426

Name/school/expertise

Members: Youjiang Wang Georgia Tech Mechanics of fibrous structures

John Mi Cotton Inc. Textile Engineering

Objective:

To develop a new method for measurement of fiber-on-fiber friction in textile manufacturing processes based on the frictional energy dissipated in dynamic loading of a fiber assembly, including (1) to develop a new theoretical model for characterization of inter-fiber friction from frictional energy loss of a fiber bundle subjected to dynamic loading; (2) to design and build a set of instrument for measurement of fiber-on-fiber friction energy; (3) to determine the effect of various environmental factors such as moisture content, temperature, loading frequency and fiber mechanical properties on friction energy loss of fibrous assembly.

Relevance to NTC Mission:

Friction plays a paramount role in textile manufacturing and end-use behavior of textiles. The fundamental understanding of fiber friction behavior to be gained in this project will help the US textile industry to develop new, better products, and to improve the manufacturing processes for better quality and efficiency. Graduate students will be trained in this critical field. The project will be jointly conducted between NTC institutions and the industry.

State of the Art:

Fiber-on-fiber friction is one of the most important fiber characteristics or properties in textile manufacturing processes and the performances of the final products. For example, it is the frictional force between neighboring fibers that holds the fibers in a staple yarn together. In spinning, knitting and weaving processes, the friction of fibers creates tension on yarns. The friction of fibers translated to the yarn friction properties also determines properties of fabrics. Tensile, bending, and shear properties of a fibrous assembly is largely dependent on the friction between fibers. Drape of a fabric relies on the friction between yarns and fibers in a fabric.

A lot of research has been carried out on fiber-on-fiber friction including an NTC project conducted by El Mogahzy and coworkers. Almost all the approaches to date measure the frictional force in either a tensile or a compressive test of a fiber bundle or the like. The friction properties of fibers are then characterized according to the classic definition of friction between two flat surfaces (e.g., the frictional force is assumed to be equal to the normal force times the friction coefficient). Because of the complex nature of fiber friction, the friction coefficient value has been found to be strongly dependent on testing condition.

In literature, little attention has been paid to frictional energy loss due to fiber-on-fiber friction. Hertel and Lawson reported a shear friction measurement of textile fibers using a simple oscillating pendulum. The energy loss due to inter-fiber friction was calculated from the difference between the amplitudes of two consecutive swings, and the normal force applied to the top plate of the devise. A shear friction calculation was given as:

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where K is a constant determined by the load and the specimen area, A₀ and A_n are the amplitudes of the first and the nth swing, and T is the applied normal force. This method explored the dynamic and static frictional energy loss in fiber-on-fiber shear friction. However, in that study, the shear friction, S, was not clearly defined and the energy loss due to intermolecular friction of the fiber was neglected. In addition, this method can only estimate the frictional energy at very low frequencies due to the slow swing nature of the pendulum mechanism.

In our preliminary study, a cotton roving with different twist levels (1.5 and 3 tpi), different cyclic loading frequencies (1 and 10 Hz), and different gage lengths (9, 29 and 50 mm) was cyclically loaded. The data indicates that when frictional force induced by higher twist increases the inter-fiber frictional energy loss also increases substantially. The higher the frequency of the cyclic loading, the higher the energy loss. A gage length significantly shorter than staple length results in a considerably lower energy loss due to lack of relative movement of the fibers. The results are plotted in following figures.

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Approach:

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Based on the theory of dynamic mechanical analysis of polymers, a theoretical model on the fundamental phenomenon of fiber-on-fiber friction under dynamic loading is being formulated. A novel test technique based on the theory is under development in which the fiber assembly is subjected to cyclic loading conditions and the energy loss due to fiber-on-fiber friction is calculated. The fraction of energy loss due to intermolecular friction is excluded from the total energy loss using a single fiber or extremely short fiber bundles. In this project, we want to further develop the theory and collect experimental data of frictional energy loss of fibrous assemblies using a testing system that is developed in the first year of the project. The schematic of the testing system is as follows:

Because of the complicated nature of fibrous structures and the influence of environmental factors encountered in the measurement, the results of the test will be analyzed using cross-correlation and other advanced data analysis techniques. This new method will allow us to evaluate the change of fiber-on-fiber friction due to the variation of fiber surface properties, moisture content, temperature, fiber linear density, fiber mechanical properties, and yarn and fabric structures.

This Year’s Goal:

Further develop the theoretical model for the analysis of the relationship between frictional energy of fibrous assemblies and various other fiber properties and fiber strand geometry under dynamic loading conditions.
Complete fabrication of an experiment fixture for testing and analysis of fiber-on-fiber frictional energy loss.
Systematically test roving of fibers with different fiber contents and structures under various loading conditions.

Outreach to Industry:

This research will be a joint effort among industry and academia. Fundamental studies will be carried out at Georgia Tech and NCSU in cooperation with Cotton Inc. and other potential participants. The work will be of interest to many textile manufacturers, fiber producers, and machinery companies. Project results will be disseminated through conferences and publications. Graduate students trained in this project may also bring the expertise to the industry directly.

New Resources Required:

The project is carried out by a multidisciplinary team consisting of members from NTC institutions and industry. Some testing and data processing facilities are available at NCSU and Georgia Tech and will be used extensively. Since no commercial instruments can satisfy our needs, a prototype test instrument specifically designed for this test will be fabricated.