Needle Punch
Needle-punched nonwovens are felt-like and very flexible, having a fibrous network with distinctive pores, which makes them suitable for applications in filtration and drainage. The needle-punched nonwoven geotextiles are entangled to form a complex 3D structure by random fibres, accounting for its bulky nature, wide range of pore size distribution, and good drainage. Needle-punched nonwovens have periodic regions in their structure that are caused by the interaction of fibres with needle barbs. Fibre segments are reoriented and migrated from the surface of the web towards the interior of the fabric and become perpendicular to the plane. This rearrangement of fibres due to processing increases the structural anisotropy as compared with the original web, and therefore, the structure of needle-punched fabric is not homogenous. In addition, needle marking caused by the punching effect of needles is frequently visible on the fabric surface. The shape and number of holes depends on the number of needles in the needle board, the size of needles, advances per stroke, punching density and fibre type.
Key properties that can influence the performance characteristics of a nonwoven needle-punched geotextile are: fibre type: polymer, diameter, length, etc.; fibre quality; fibre lubrication; needle shape; needle density; depth of penetration of needle, needling rate, and batt areal densit.
Needle-punched nonwoven geotextiles are extensively used in civil engineering applications, including road and railway construction, landfills, land reclamation, sea defence, and slope stabilization. Needle-punched nonwovens are commonly used for applications offering cushioning and reinforcement against subgrade surface irregularities. These surface irregularities can impact concentrated forces perpendicular to the plane of the geotextile, leading to its puncture failure. Subsequently, the needle-punched nonwoven may not be able to carry out geotechnical functions effectively. Hence, it is imperative to understand the failure analysis of the nonwoven such that an appropriate ‘design criteria’ of geotextile can be prescribed. Such applications require certain functional characteristics in the structure, besides basic properties, which are required to be engineered by judicious optimization of the needle-punching process. These applications are required to perform more than one function, ie, filtration, separation, protection, drainage, and reinforcement .