TIBTECH innovations


Crimping for connection of heating or conductive yarns within a multi-layer fabric or composite part or mold

Connections with our heating or conductive yarns can cause hot spot risks. This risk is even more important when high powers are involved, for heating molds or composite parts for instance.

Within flexible structures, vibration and industrial washing withstanding are key for these connection .

Welding, crimping or screw-connectors?

Most of the resistive based alloy yarns we manufacture are note weldable. Therefore we recommend to use crimping connections.

What about usual screw connections?

Our flexible conductive yarns are made from a high number of ultra-thin filaments to improve their fatigue life. As you can see on the drawing below, a single screw connection will only connect a few number of the fibers through the screw or the internal surface of the connecting device. As we work with resistive fibers, all the current will go through this limited number of fibers before the load can spread through the whole cross section of the wire. This will cause over heating of these fibers and a very dangerous hot spot in the vicinity of the connection point.

multifilament screw-connection

What kind of connections do we recommend?

To get an ideal connection, all the fibers of the cross section should be in direct contact with the conductive material of the power input connector. In reality, we consider a connection as acceptable when all the fibers on the external layer of a yarn are in direct contact with the power input cable or the crimping connector on a sufficient length.

 crimp length related to yarn pitch

What can be used as a crimping connector?

The connection shall be a 'cold spot'. To do so, the connector materials must be very conductive (copper or aluminium for instance). The shape of this connector shall be a small tube just fitting the diameter of the heating wire, plus the diameter of the conductive yarn (see picture below). Many solution exist on the market, most of time with an outside thermo-shrinkable insulating material.

 optimal crimp related to yarn pitch

 crimp related to very thin threads

How to manage fatigue issues at the crimp and thin flexible wire interface

The interface between the rigid connector and the flexible heating yarn is where the strain applied to the heating wires is the highest. As a result, it is where the fatigue issues usually occur. If a wide angle of movement exist, we recommend to move the connector to an area where these movements are more limited or to add a movement limitation device or a thermo shrink sleeve.

 risk of thin wire break between rigid and flexible zone

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