Concepedia

Picture Frame Test of Woven Composite Reinforcements with a Full-Field Strain Registration

Stepan Vladimirovitch Lomov, Anne‐Marie Willems, Ignace Verpoest, Ying-Jie Zhu, Marcin Barburski, Tz. Stoilova

Textile Research Journal · 2006 · 116 citations · 9 references

TL;DR

The study investigates how shear diagrams vary with test conditions, whether fabric shear differs from pure shear, the magnitude of local shear variations, and how fabric shear translates into yarn deformations. The authors conducted picture frame shear tests with optical strain registration on various glass and glass/PP woven fabric reinforcements. The tests on glass and glass/PP woven fabrics revealed that sample pretension dominates shear behavior, with negligible deviation from pure shear, local shear variations within 2°, and distinct yarn rotation followed by lateral compression stages.

Abstract

Results of picture frame shear tests with optical registration of the strain fields are presented for glass (plain and twill, three types) and glass/PP woven (plain and twill) fabric reinforcements for composite materials. Four problems were investigated. (1) How does the shear diagram vary with differences in test conditions? The major factor is the sample pretension, which is influenced by its gripping, removing/preserving yarns near the grips and “conditioning” in the shear cycles. (2) Does the shear of the fabric differ from the pure shear prescribed by the frame? The differences are normally negligible. (3) How large are the variations of the local fabric shear? The scatter of the local fabric shear does not exceed 2°. (4) How is shear of the fabric translated into deformations of the yarns on the micro-scale? Different stages of the fabric deformation are identified: rotation of the yarns followed by their lateral compression.