Introduction: Bending rigidity is an important property of textiles that affects their draping, handle, and overall quality. It is a measure of the resistance of a fabric to bending, and is determined by the force required to bend a fabric through a given angle. In this lab experiment, we will determine the bending rigidity of a fabric sample using the HEART loop method.

Objective: The objective of this lab experiment is to determine the bending rigidity of a fabric sample using the HEART loop method.

Materials:

- Fabric sample
- HEART loop bending rigidity tester
- Clamp
- Balance
- Ruler
- Calculator

Procedure:

- Cut a rectangular fabric sample measuring 5 cm x 10 cm.
- Attach one end of the fabric sample to the clamp of the HEART loop bending rigidity tester.
- Pass the fabric sample through the loop of the tester and attach the other end of the fabric sample to the balance.
- Adjust the height of the balance so that the fabric sample hangs vertically.
- Set the initial angle of the fabric sample to 41.4 degrees.
- Release the fabric sample and measure the time it takes to complete 10 complete oscillations (swings) using a stopwatch.
- Record the time taken to complete 10 oscillations in seconds.
- Repeat steps 5-7 for 10 different angles of the fabric sample, ranging from 30 degrees to 90 degrees in 5-degree increments.
- Using the formula below, calculate the bending rigidity of the fabric sample for each angle:

Bending rigidity (mg.cm²) = 50 x (sample weight in mg) x (oscillation period in seconds)² / (loop length in cm)³

- Plot a graph of bending rigidity (mg.cm²) against the cosine of the angle (cosθ), where θ is the angle of deflection.
- Determine the slope of the graph, which represents the bending rigidity coefficient (C).
- Calculate the bending rigidity of the fabric sample using the formula:

Bending rigidity (mg.cm) = C x (sample weight in mg) x (loop length in cm)³ / 50

Results: Record the time taken to complete 10 oscillations, loop length, and bending rigidity for each angle tested. Plot a graph of bending rigidity against the cosine of the angle and determine the bending rigidity coefficient (C).

Discussion: Discuss the importance of bending rigidity in the textile industry and how it affects the draping, handle, and quality of fabrics. Analyze the results obtained from the experiment and discuss any trends observed in the bending rigidity values. Compare the bending rigidity of the fabric sample with industry standards and evaluate its quality. Suggest further experiments that could be conducted to investigate the bending rigidity properties of textiles in more detail.