Aim: To determine the Specific Handle Force of the given set of fabrics.
Instrument used: SHF tester, Lab Model.
Scope, Significance & application: This instrument serves for the determination of Specific Handle force of fabrics and is suitable for all dress materials. This property includes all the deformations like bending, shear, compression, surface and Tensile at one step. The instrument was developed by Spivok as a research model and till date it is used as table model
Principle: A circular fabric specimen of 250mm diameter is withdrawn through a bush attached to a constant rate of traverse and the energy required to withdraw is recorded from the analog instrument.
Description: A simple apparatus (Fig), designed for this method, was used for determining the handle force. The apparatus consists of a spring balance (S), a highly polished stainless-steel bush (B) attached to a platform (P), and motor (M) to move the bush from top to bottom over the fabric specimen of 25 cm diameter. A steel wire is attached to the spring balance, and this passes through a bush made of highly polished steel. The inner hole radius of the cylindrical bush was varied from 18mm to 28mm radius to suit the various types of weft-knitted fabric. Various diameters were selected on the basis of the fabric, weighting in grams/sqmt, and were used in the evaluation.As the hole radius changes, the hole inside surface area (A cm2) will change which, in turn, will affect the value of the fabric hand force (F) as the frictional area between the withdrawn fabric and the hole will change. Thus for obtaining a comparative fabric specific handle force (SHF) irrespective of the samples thickness, the hole surface area (A), the fabric handle force (F) must be divided by the packing fraction (B), and the area (A cm2). Therefore the specific handle force is obtained from the equation as given below:
The packing fraction (B) has been defined as the ratio of the maximum fabric material volume to the inside ring hole volume.Therefore
This method of normalising handle has been suggested by Pan (1995). It is to be noted that this represents a better measure of the specific handle force (SHF) than the method followed by Grover et al., (1993). The cylindrical bush was well cleaned with methyl alcohol before a test was done. The platform, in which the stainless steel bush is mounted, was moved by a motor and the peak load registered by the spring balance was noted. The maximum load reached on the spring balance was noted down and the mean of 20 readings was taken side by side. Figure 8.2 show the apparatus used in the study. Since it was known that variability is high in this method, it was decided to carry out 20 tests.The forces involved in the initial deformation are related to the bending modulus and the shear stiffness of the fabric. The compression and fabric friction play a larger role as the fabric specimen is squeezed to the dimensions of the ring. Fabric withdrawal force depends on the resistance to beinding, shear, compression and sliding force. The force generated depends not only on the fabric properties, but also on the ring size, and sample size. The maximum withdrawal force can be taken as a measure of fabric handle force.
Procedure: A circular specimen of 250mm dia is passed through the bush and the force required to withdraw from the bush is recorded . The experiment is repeated atleast for 25 replications and the average force is reported . To get the specific handle force the instrument reading is divided by the GSM of the fabric.
Result: The average SHF is reported ..
Testing Conditions: The specimens should be conditioned and tested in a standard testing atmosphere. Selvedges, piece ends and creased or folded regions should be avoided.
Observations and Calculations:
Atmospheric Conditions.
Specifications of fabric (Geometrical parameters)
Sample size 250mm circular specimen.
Mean Withdrawal force : GSM of the fabric: , Specific Handle force : Withdrawal Force / GSM
Standard deviation
Co-efficient of variation
Factors affecting the SHF
Type of fibre
Nature of Count
Cover factor
Type of Weave
Type of Weave
General Trend:
1.Finer the fibre or Count lower is the Force.
2. Among the Man made fibrs, Regenerated fibres and Cotton the order can be written as
Manmade Fibres < Regenerated Fibres < Cotton fibres
3. Among the Natural fibres
Silk< Cotton < Jute , Wool