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Fabric Drape and Its Measurement
Fabric drapability is a morphological characteristic occurring when fabric is hanging down for its gravity. It is one of the important indicators to measure clothes close fitting. Some fabrics like dresses, curtains, table cloths are required to a good drapability. Whether fabric drapability is good is close related to fiber classification, fiber stiffness, yarn twist, fabric density, organizational structure, etc.
There are two methods to test fabric drape: evaluated by sense or evaluated by testers (commonly used). A circular sample (Figure 7) with a certain area is put on sample clamping plate, overlapping their centers, so that the drape sample comes for drooping along the circular plate due to its gravity.
- Drape Test
Experimental Apparatus and Materials
Fabric Drape Tester (Figure 8), Scissors, pen, fabrics, etc.
The drape sample is projected onto a white sheet, and digital camera is used to obtain sample’s drape figure through which we can get some specified quantitative information regarding fabric drapability. The relevant indexes as drape coefficient and drape wave number can be got from computer image processing technology. Generally, fabric drapability is evaluated by drape coefficient “F”. Drape coefficient is the ratio of the projected area to original area:
F= [(S3-S2) / (S1-S2)] * 100%
S3-the Pojected Area
S2-the Area of Clamping Plate
The bigger the drape coefficient, the stiffer the fabric and the weaker fabric drapability; vice versa. We can get a comprehensive understanding of the fabric drapability through drape wave number and amplitude.
A. Sample Preparation
3 samples of a diameter of 24cm are prepared, with no crease on surface. Each circular sample should be opened a 4mm pore in the center. Two sides of each sample should be marked “a” and “b” respectively.
B. Test Procedure
- Click “NEW” to establish a new test. A side of sample upward is put on the down clamping plate to make sure that the positioning column pass through the pore, and the up clamping plate is put on it.
- Time starts counting from the up clamping plate being put on the sample. 30s later, the projected image of fabric is taken by the digital camera. Click “REAL-TIME ACQUISION” below “ACQUIRE IMAGE” in “IMAGE” menu. Click “DIRECT SHOOTING” to show the “REMOTE CAPTURE Dc” dialog box. Click “LOOSE THE SHUTTER” to get a static figure (Figure 9) in the dialog box, and finally get a fabric projection (Figure 10).
- Through computer processing software, we can acquire drape coefficient, drape wave number, amplitude, etc.
- The b side of sample above mentioned is upward, repeated the above test procedures.
- After finishing shooting, “REMOTE CAPTURE Dc” dialog box is closed. Click “CORRESPONDING INDICATORS” to check the corresponding indicators.
- The average value of drape coefficient is calculated in “a” side and “b” side of each fabric. And calculating the total average value of sample’s drape coefficient.
The dynamic drapability can be measured, which makes you go further in fabric drapability. The procedures are as follows:
- Open the static and dynamic switch. Sample is rotated at the speed of 100r/min in 45s.
- When fabric stops rotating, with second chronograph counting, the static drape image of fabric is taken by digital camera after the 30s.
- Re-open the static and dynamic switch. Sample is rotated at the speed of 50~150 r/min. When the rotation of fabric is stable, the dynamic drape image of fabric is taken by digital camera.
- Computer and evaluation software is used to obtain static and dynamic drape coefficient, drape wave number, overhanging morphological change rate, etc, according to the images.
- Result calculation
a.Drape Coefficient (same as the above)
b.Overhanging Morphological Change Rate:
L= (Ds-Dm) / Ds
L – Overhanging Morphological Change Rate
Ds – Static Drape Coefficient
Dm – Dynamic Drape Coefficient