Measuring the natural frequencies of knitted materials for protection against vibration

In this study, the use of knitted structures as potential vibration isolators or parts of protective equipment is proposed. Four types of knitted structures were made from different yarns by varying the stitch depth. By combining these variables, a series of 48 patterns were tested for vibration isolation using the free vibration method to measure their natural frequencies. Knowledge of the natural frequencies of textiles is necessary when designing a material to protect it from vibration, in order to avoid the phenomenon of resonance that occurs when the excitation frequency of an external force overlaps with the natural frequency of the system. From the recorded values of the frequencies, it is possible to infer some properties of the knitted materials. The value of the natural frequency of any material gives information about the stiffness of the material. The higher the natural frequency, the more stiffness can be expected. The shape of the natural frequency curve is relevant to the material’s ability to dampen vibrations. The smoother the shape, the higher the damping capacity of the material. The study shows that the yarn type and the structural parameters of the fabric affect the vibration behaviour. The tightness of the fabric is one of the most important variables affecting the level of natural frequencies of the material. This research is expected to support the development of knitted fabrics as good vibration isolators for humans by also showing their comfort level compared to alternative materials used so far.