It is shown how the method of measuring fabric drape by supporting a circular specimen of fabric between smaller horizontal circular plates has been modified to allow a more sensitive test to be made on very stiff and very limp fabrics. The use of diverging light instead of parallel light is described, and the correction of the results for this change is calculated. A method of determining the drape coefficient by a paper-weighing method is also described.
Thirty two tufted carpets, representing variations in fiber content, pile weight, and cut and loop-pile construction were studied for stress-strain behavior under cyclic loading to 12 lb/in.2 on an Instron tensile tester. Results are presented conventionally in terms of compression, recovery, matting, and resilience. In addition, a relationship, which appears to be responsive mainly to the type of fiber in the pile yarn, was developed between the compressive force per unit weight of pile yarn and the percent compression of the pile. On this basis, no major difference was found in the relative stress-strain behavior of the carpets before and after exposure to 100,000 revolutions of the Tetrapod Walker.
The Tetrapod Walker machine was evaluated as a device for the accelerated testing of carpets. Tufted carpets were prepared from wool, nylon, acrylic, and polypropylene yarns, in both cut-pile and loop-pile construction. Four levels of pile weight, obtained by varying the number of tufts per inch, were prepared for each carpet. The percentage loss in pile height resulting from exposure in the Tetrapod Walker was found to be a linear function of the logarithm of the number of revolutions of the Tetrapod Walker. This function was characteristic of each carpet. Specifications for a tentative test method were developed. The method involves measurement of the percentage decrease in pile height after exposure of the carpet sample to 50,000 revolutions (overnight operation) of the Tetrapod Walker. Studies on the compression and recovery properties of these carpets will be reported in a subsequent paper.
The dependence of the drape of fabrics on bending stiffness and shear stiffness has been investigated. A version of the Fabric Research Laboratories Drapemeter is described, and the drape coefficient obtained is used as a measure of the fabric drape. The regression of the drape coefficient on bending length for a large number of fabrics was highly significant, and the addition of shear stiffness to the regression made a highly significant difference. The regression equations provide the relations between the variables for the conditions used. Theoretical values of drape coefficient for zero shear stiffness were lower than the measured values.
Thickness measurements have been made on carpets during floor trials. Under the conditions of these trials, the loss of thickness was found to be linearly related to the logarithm of the number of treads. This relationship provides a useful measure of the rate of loss of thickness.
A résumé of the methods of production of non-woven (bonded fibre) fabrics is given. Measurements of the following physical properties have been carried out on a range of commercially available parallel-laid, cross-laid, random-laid, composite, and perforated non-woven fabrics: weight, thickness and density; tensile stress-strain curves, giving modulus, yield point, breaking point and anisotropy; stress relaxation; elastic recovery; bursting and tear strengths; bending length and crease-recovery; and, in some instances, shear modulus and drape coefficient. The results show the range of available properties. In addition, certain correlations between various physical parameters have been found, establishing a fairly rational pattern of behaviour and giving some indication of the factors governing this behaviour.
As part of a study of fabric drape, the fabric-shearing apparatus due to Mörner and Eeg-Olofsson has been built and studied. Methods of expressing the results are given and the variability of the results has been measured. The effect of tension on the specimen has been measured and a model is given which may be used to explain the shape of the hysteresis diagrams.
An experimental technique used for measuring resistances along the length of fibres up to 1015 ohm compared to 1012 ohm in an earlier investigation is described. The paper gives results of measurement of the resistance of synthetic fibres and cellulose acetate, between 33 per cent, and 98 per cent relative humidity.
