What is Fabric Drape?
Drape is the term used to describe the way a fabric hangs under its own weight. Fabric drape is not a mechanical or physical hand property but an important aesthetical parameter of fabrics. Drape is an important component of the aesthetic appearance and appeal of garments, and also plays a crucial role in garment comfort and fit. Drape appearance depends not only on the way the fabric hangs in folds, etc., but also upon the visual effects of light, shade and fabric luster at the rounded folds of the fabric as well as on the visual effects of folding on color, design and surface decoration. It is a complex property including bending and shearing deformation. Drape is important for the selection and development of textile material for garment industry. Fabric drapability may be described as a degree of the deformation of fabric to orient itself into folds, when the fabric is partially supported by other objects.
Drape has an important bearing on how good a garment looks in use. The draping qualities required from a fabric will differ completely depending on its end use, therefore a given value for drape cannot be classified as either good or bad. Knitted fabrics are relatively floppy and garments made from them will tend to follow the body contours. Woven fabrics are relatively stiff when compared with knitted fabrics so that they are used in tailored clothing where the fabric hangs away from the body and disguises its contours. Measurement of a fabric s drape is meant to assess its ability to do this and also its ability to hang in graceful curves.
Measurement of Fabric Drape by Cusick’s Drapemeter:
Drape determines the adjustment of clothing to the human silhouette and is defined as the extent to which a fabric will deform whilst hanging under its own weight. The ability of a fabric to drape can be seen as the main distinction between textiles and other sheet materials. An important measurement device is the drapemeter, where a circular piece of fabric is placed over an inner circular disc and an outer annular disc. During the drape test, the sample is placed over the two discs and the outer annular disc is lowered gradually, allowing the fabric to drape inside.
Cusick developed a drapemeter, where one characteristic value, the drape coefficient, is calculated for a tested fabric. Cusick’s Drapemeter is still the standard method of measuring drape and is widely used even today. The drape coefficient can be defined as the percentage of the area of the annular ring covered by a vertical projection of the draped fabric. A high drape coefficient means that there is little deformation and vice versa.
In the drape test the specimen deforms with multi-directional curvature and consequently the results are dependent to a certain amount upon the shear properties of the fabric. The results are mainly dependent, however, on the bending stiffness of the fabric.
During draping, a fabric undergoes large deflections but very small strains due to its high flexibility, with by far the largest deflections coming from bending, with only a small component being due to in-plane extension and shear deformation.
In the test a circular specimen is held concentrically between two smaller horizontal discs and is allowed to drape into folds under its own weight. A light is shone from underneath the specimen as shown in Figure 1 and the shadow that the fabric casts, shown in Figure 2, is traced onto an annular piece of paper the same size as the unsupported part of the fabric specimen.
The stiffer a fabric is, the larger is the area of its shadow compared with the unsupported area of the fabric. To measure the areas involved, the whole paper ring is weighed and then the shadow part of the ring is cut away and weighed. The paper is assumed to have constant mass per unit area so that the measured mass is proportional to area. The drape coefficient can then be calculated using the following equation:
…………… …… ………….Mass of shaded area
Drape co-efficient = ———————————————— x 100%
……………. …………..Total mass of paper ring
The higher the drape coefficient the stiffer is the fabric. At least two specimens should be used, the fabric being tested both ways up so that a total of six measurements are made on the same specimen. There are three diameters of specimen that can be used:
- 24cm for limp fabrics; drape coefficient below 30% with the 30cm sample;
- 30cm for medium fabrics;
- 36cm for stiff fabrics; drape coefficient above 85% with the 30cm sample.
It is intended that a fabric should be tested initially with a 30cm size specimen in order to see which of the above categories it falls into. When test specimens of different diameter are used, the drape coefficients measured from them are not directly comparable with one another.
References:
- Physical Testing of Textiles by B. P. Saville
- A Practical Guide to Textile Testing By K. Amutha
- Engineering Apparel Fabrics and Garments by J. Fan and L. Hunter
- Clothing Appearance and Fit: Science and Technology by Fan, W. Yu and L. Hunter
- Modeling and Simulating Bodies and Garments Edited by Nadia Magnenat-Thalmann
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
