Improving the accuracy of the uniaxial bias extension test on engineering fabrics using a simple wrinkle mitigation technique

Abstract

In response to a previous investigation on the influence of specimen pre-shear and wrinkling on the accuracy of uniaxial bias extension test results [1], numerical and experimental investigations have been conducted, aimed at evaluating the use of transparent anti-wrinkle plates to mitigate errors due to wrinkling of engineering fabrics. Predictions of the numerical investigation suggest that the anti-wrinkle plates significantly improve the accuracy of kinematic measurements while introducing only a very minor stiffening effect on the axial force versus shear angle data. Results from subsequent experiments on two different engineering fabrics confirmed the numerical predictions; the accuracy and repeatability of test data was significantly improved and the maximum shear angle and axial force data measurable in the tests was significantly increased. The investigation suggests a useful role for anti-wrinkle plates in characterising the formability of engineering fabrics.

A macroscale finite element approach for simulating the bending behaviour of biaxial fabrics

“…Wrinkles are often observed during material characterisation tests, such as the bias extension or picture frame shear tests [13][14][15] for determining the in-plane shear resistance of fabrics. Whilst this deformation is useful for determining the "shear locking angle" to quantify the severity of yarn compaction, the onset of wrinkling can produce inaccuracies in the measured shear angle during the test [16,17]. Shear induced wrinkling can be delayed or prevented in picture frame shear testing due to small tensile forces generated along the fibres by the clamps [18], whereas bias extension testing is quite sensitive to shear induced fabric buckling as the vertical specimen edges are unconstrained.…”

Design of buckling and damage resistant steered fibre composite laminates using trellis shear kinematics

“…The upper limit of 𝜃 𝑚𝑎𝑥 is set here at 45° which makes the highest shear angle of the entire pattern about 49°, this is a conservative value that should avoid potential manufacturing issues when aiming to form the steered sheet. In [31], the measured wrinkle onset shear angles of both glass and carbon-fibre fabrics were greater than 50°. Note that the practical manufacture method will be discussed in a future investigation, here we simply assume that manufacture is possible.…”

Characterization and analysis of wrinkling behavior of glass warp knitted non-crimp fabrics based on double-dome draping geometry

“…43 Many adjacent buckles could be considered as a wrinkle according to the definitive criterion. 55 Also, another defect can be added, which could irregularly appear in some cases; stitches dislocation: where it is a disturbance in stitches' location from their proper place. 29 This defect was accompanying some severe buckles in the deformed fabric, especially when there was a set of roving bigger in size than other sets, an example shown in Figure 8, and it happened irregularly.…”