Introduction

Most nonwoven products are in 3D form. They have to be made from flat fabrics through costly conversion processes. The joints in the product can also be a problem due to their deviation from the normal fabric.

Research in nonwovens is mainly related to the manufacture and use of the fabric in 2D sheet form, although there have been a few reports on the production of 3D nonwovens. We present in this paper a new technology for the production of 3D nonwovens from staple fibres and discuss the design of the fibre flow system using CFD techniques.

Process Design

The process is based on the air-laying principle for web formation and thermal through-air bonding for web consolidation (Figure 1). The fibre-opening unit is based on a roller card. The fibres are dispersed in airflow and carried to perforated 3D moulds. The moulds move across the machine width during web formation and into a separate bonding section for consolidation.

The airflow velocity and pressure distributions in the web forming area are critical for achieving the desired fibre distribution over the 3D mould surface. These can be studied using CFD technology. We used the Fluent CFD package in our study. Figure 2 shows an example of air velocity distribution in various cross sections of the air duct. A variety of 3D shapes can be formed with a controlled fibre distribution within the 3D shell structure by optimising the design of the air duct and the mould chamber, the airflow velocity and also the design of the appropriate airflow control devices. Airflow control is essential because the angle between the airflow and the 3D mould surface varies. It is also important to avoid vortex in the airflow because it will cause fibre entanglement.