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August 09, 2016
Fabric Weave: The effect of balanced vs. unbalanced weaves

Posted by: Casey Whalen

We often receive questions about the ideal pipe repair systems given varying external conditions. Our recommendations are predicated upon the fabric weave that is most appropriate, in addition to other factors. Consider that typically, a single strand of fiberglass has one-third the modulus of an equivalent strand of carbon.

Common classifications for fabric weaves include uni-, bi- or tri-directional:

FormaShield – unbalanced tri-directional

A+ Wrap – unbalanced bi-directional

Atlas – unbalanced bi-directional

Uni-directional systems have fibers all running in the same direction. In bi-directional systems, individual fibers run along the length of the fabric and are perpendicular to it. The FormaShield system is tri-directional and has fabric running along the length of the pipe as well as diagonal (45°) fibers. Once wrapped on a pipe, all values are measured as either hoop direction or axial direction with respect to the pipe. Balanced weaves have the same amount of reinforcement in the hoop direction as in the axial direction.

The A+ Wrap and Atlas systems have an unbalanced weave. In this instance, this means there are more fibers present in the hoop direction than in the axial direction. Pipe Wrap typically has unbalanced weaves as the majority of pressure containment occurs only in the hoop direction. However, some axial reinforcement is necessary to counteract bending moments or axial tension, therefore uni-directional fabric is not used.

The effect of balanced vs. unbalanced can be seen by examining system properties in the graphic below. By examining this data, it is clear that Atlas has far superior mechanical properties in the hoop direction:

Fabric_Weave_Chart.png

Interested in learning more from Casey and our experienced team of engineers or discussing the best solutions for your next pipe repair project? Contact us with questions today.

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Category: Pipe Wrap

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