Effects of warp knitted fabrics made from multifilament in cement-based composites: Fid-Bau Portal

Effects of warp knitted fabrics made from multifilament in cement-based composites

Cohen, Zvi / Peled, Alva / Pasder, Yonatan / Roye, Andreas / Gries, Thomas

In this work weft insertion warp knitted fabrics made from multifilament yarns as reinforcements for cement composites were studied. Influences of parameters related to these knit fabrics such as loops size, bundles size (number of filaments), and fiber type such as Aramid, AR glass, High Density Polyethylene (HDPE), and polypropylene (PP) on tensile performances of cement composites were examined. A correlation between mechanical performance of the fabrics themselves (not in a matrix) and the fabric-cement composites was examined. All composites in this study were prepared by the Pultrusion process. In warp knitted fabrics, warp and weft yarns are connected by stitches (loops). Decreasing the number of loops per unit length in a knit fabric improves the fabric's mechanical performance, as observed in this work. On the contrary, a larger number of loops per unit length provides more anchoring points and thus stronger anchorage with the cement paste. However, stitches tighten the filaments in the bundle and prevent spaces from being opened, thus they reduce the matrix penetrability. As their number increases, their size decreases, further reducing the matrix penetrability and overall composite performance. The optimal loop size is a combination of these different factors. Based on the present work, it can be concluded that a knit fabric produced with a large diameter bundle is more sensitive to cement penetrability and therefore highly affected by the knitted fabric loop size. In this case, the optimal loop size was found to be 4 mm and therefore provides the best composite performance. When a thinner bundle is used to produce the knit fabric, cement penetrability is much easier and therefore, the influence of the loop size is less significant. A complementary study is needed in order to get more accurate conclusions regarding influences of knit fabric structures including loop size on bonding, cement penetrability and composite performance, as well as development of a mathematical model. The influence of different fabric materials shows a high strengthening of TRC with Aramid and HOPE yarns, mainly at large strains. The results brought in this study indicate the massive potential uses of those TRC components, such as airport pavement, dams, construction in places endangered by earthquakes and many more.