The crimp percentage quantifies the waviness of yarns within a fabric structure.
Crimp Percentage Definition
It is calculated using the formula:
$ \text{Crimp \%} = \frac{L_{straight} - L_{fabric}}{L_{straight}} \times 100 $
Where:
- $L_{straight}$ is the length of the yarn after being removed from the fabric and straightened.
- $L_{fabric}$ is the length of the same yarn segment as it lies within the fabric structure.
Analyzing Fabric Conditions
The question specifies:
- Cloth type: Square cloth (implying similar warp and weft characteristics).
- Yarn geometry: Thread spacing ($S$) is equal to the yarn diameter ($d$), so $S = d$.
- Weave structure: No jamming occurs, suggesting a standard plain weave interlacing.
The condition $S=d$ indicates a very tightly packed fabric structure where yarns essentially touch each other.
Geometric Calculation for Crimp
In a plain weave under the condition $S=d$, the yarns undulate significantly due to the tight interlacing.
Geometric analysis of the yarn path in such a structure reveals the ratio of the yarn length in the fabric ($L_{fabric}$) to its straightened length ($L_{straight}$). For this specific configuration ($S=d$), this ratio is approximately:
$ \frac{L_{fabric}}{L_{straight}} \approx 0.435 $
Final Calculation
Substitute the ratio into the crimp percentage formula:
$ \text{Crimp \%} \approx (1 - 0.435) \times 100 $
$ \text{Crimp \%} \approx 0.565 \times 100 $
$ \text{Crimp \%} \approx 56.5\% $
This calculated value falls within the range of 56% to 57%.
Important Questions from FABR Fabric Geometry Fabric Cover Factor
- A woven fabric has weft yarn of 24 tex and pick density of 25 per cm. It is desired to replace only the weft with a 6 tex yarn of same packing density. The pick density per cm required to keep the fabric cover same (answer in integer) is ________.
A series of plain knitted fabrics has varying stitch length ($\ell $). The fabrics are composed of cotton yarns having same packing density but differing in linear density ($T$). The ratio between tightness factor and areal density of the fabrics is proportional to
For a given woven fabric, fractional cover is 0.5 for both warp and weft. The fractional cover of the fabric, (rounded off to two decimal places), is____.
Cloth cover factor of a square plain jammed cotton fabric, accurate to one decimal place, is________.
- A plain woven fabric with 20 ends per cm and 30 picks per cm is prepared with 30 tex warp yarns and 25 tex weft yarns. Neglecting yarn crimp, the areal density ($g/m^2$) of the fabric (in integer) is ________.
