Objective measurement is a scientific way to get a good understand about some basic properties of fabric. In this lab, FAST system can provide the accurate measurement to show compression, extension, bending and stability of fabric. The aim of this test is to predict how a fabric will perform when made up into a garment. For fabric manufactures,finishers and garment manufacturers, they can use the results of this test as a basis to do fabric specification, product and process development, quality assurance and process control(Giorgio M. Pier, 1995).
2.1 Test Methodology
The F.A.S.T system, which was developed by the Australian International Wool Bureau, consists of three simple instruments and a test method. The FAST-1 compression meter gives a accurate measurement of fabric thickness at various load, and then surface layer thickness can be easily calculated. With FAST-2, the fabric bending length can be measured according to British Standard (Standard No.BS3356-1961). In this test, bending length is converted into bending rigidity which plays an important role in fabric handle. FAST-3 is testing for fabric extensibility at various loads. According to the results of this part, the ability of a fabric to resist buckling can be revealed.
2.2 Details of Samples Examined
There are 9 fabric samples (A,B,C,D,E,F,G,H,I) which are all made up by plain-woven. According to the different sizes and types, those nine samples were divided into three groups. Table I shows the difference among those fabrics.
2.3 Apparatus & Procedure
In the test, 5 fabric samples (A,B,C,D,E) are pressed under two different loads of 2g/㎡ and 100 g/㎡ respectively. The fabric thickness is displayed with a micrometer resolution on the screen. then surface layer thickness can be calculated. First of all, put sample A on the reference surface of apparatus and give a load of 2g/㎡ on the fabric. After hearing the “beep” sound, write down the data showed on the screen. Then do the same oation with a load of 100g/㎡, write down the data of T100. Repeat the steps with sample B,C,D,E,F.
The FAST-2 works on the cantilever principle,which involves pushing a fabric over a vertical edge until it has bent to specified angle of 41.5˚. 6 samples are test in this part (warp A,B,C and weft D,E,F) light cut off the road, extending the length of the specimen holder is bending length, which can calculate the bending stiffness. At first, put the sample A on the plane of measurement instrument, then place a pressing plate on it and ensure the front of sample exceeds 10mm than the plate. Secondly, push the plate and sample forward slowly after the screen shows start. Keeping pushing until the green light turn to red, then push it back to make the light turn green again. Write down the data on the screen. The other five fabric samples are also tested in this way.
FAST-3 extension meter measures the fabric extensibility in warp, weft and bias directions under three fixed low loadings (5g/cm, 20 g/cm, 100 g/cm). Firstly, ensure the whole test is did at a stable place. Put all the weight on one side of plate and fix the sample on the apparatus. Then remove the first weight (75g), and turn the knob clockwise slowly. After hearing “beep” sound, extension of E5 is displayed on the screen. Next, remove the second weight (400g), so that E20 can be measured. Finally, removing all weights, get the data of E100. Repeat these operations with all 9 samples respectively.
Discussion of Results & Conclusions
After sorting and analyzing the FAST data, ten of them can be shown on the siroFAST CONTROL CHART FOR TAILORABILITY to assess their properties (as shown on the next page). The fingerprint of E100-1,B2 and G are in the shaded zones which means some potential problems influenced by that property is indicated. The data of F-1 and F-2 which was calculated from FAST-2 shows the good formability of both warp yarn and weft yarn, so that they will not form puckered seams either during or after sewing. Comparing with E100-1 and E100-2, it is easily to find that weft yarn of wood has a lower extensibility than warp yarn. It means warp sample can move around during cutting, but it also causes problem with sizing, pattern matching at the sewing stage, because E100-1 falls into the danger range. As it was said by Jedda, “ The parameter of bending rigidity relates to the difficulty with which a fabric can be deformed by bending.
Bending rigidity is particularly critical in tailoring lightweight fabrics.”( Jedda.H 2007) According to the chart, both of warp yarn and weft yarn have a low values of Bending Rigidity which indicates problems in cutting, handling and sewing. Shear rigidity which is calculated from the bias extensibility measured on FAST-3 can reveal the ability of a fabric to resist buckling. For the bias samples in this test, they will be easily distorted in laying-up, marking and cutting, because the data of G is under the standard.