In-plane Shear Measurements of Textile Composites with Large Unit Cells using the Plate Twist Test

Abstract

The application of the plate twist test method to 3D-woven textile composites was investigated using both numerical analyses of the test set-up as well as experimental results. Comparisons with the widely used V-notched beam shear and 10°-off-axis tension tests are introduced in an attempt to identify the true in-plane shear response. The results of this study demonstrate that with careful specimen preparation and an adequate test fixture precise in-plane shear modulus data can be obtained. Moreover, for 3D-woven textile composites with their large unit cells the plate twist test appears to be superior in revealing the “true” in-plane shear behaviour.

Determination of in-plane shear modulus of 3D woven composites with large repeat unit cells

“…The CF has been reported in various publications by Sims et al 29 (equation (2)), Gommers et al 30 and Weissenbach et al 23,27 (equation (3))…”

“…To account for the inboard shift of the contact points in the in-plane shear modulus calculation, a correction factor CF was incorporated. The CF has been reported in various publications by Sims et al 29 (equation ( 2)), Gommers et al 30 and Weissenbach et al 23,27 (equation ( 3))…”

“…A shifting factor of 0?95 was selected, which is consistent with the work of Gommers et al 30 and Weissenbach et al, 27 and it also was chosen in order to minimise the inboard shift of the contact points from the corners.…”

“…This becomes particularly important for the determination of shear performance. Weissenbach 23 examined the issue of testing 3D woven composites and focused on the experimental and theoretical determinations of shear properties. Weissenbach reviewed a number of shear testing methods including short beam shear, Iosipescu, rail shear and off-axis tension.…”

“…The use of the plate twist method is attractive because it did not require the use of strain gauges. In addition, the global material response is represented with this test technique, which would indicate that it is more suitable for testing the materials discussed in this work (unit cell size, approximately 30650 mm through the full thickness of the laminate compared with .10 mm in Weissenbach 23 ). In a review paper by Tan et al, 24 the authors reported from a numerical study by Whitney and Chou 25 on 3D woven angle interlock composite, who found the in-plane properties to be very sensitive to changes in fibre volume fraction (FVF).…”