A Study Of The Energy-Absorption Properties Of The Weft-Knitted Structural Reinforced Composites

This work mainly investigated the energy absorption properties of six different weft knitted structural reinforced composites, i.e., derived jersey, rib, interlock, derived Cardigan, spacer and Milano structural composites, under different testing conditions. The work firstly investigated the knittability of glass fibers. By adjusting suitable knitting parameters such as cam setting, feeding yarn's tension, take-down force as well as machine speed, the glass fiber weft knitted fabrics with good quality and aspects were successfully on a Stoll computerized flat knitting machine. The work then investigated the fabrication of the composites reinforced with the fabrics obtained, through VARTM process and by using two different laid-up methods. The laid-up methods included four layers parallel laid-up and four layers vertical laid-up. Finally, the work investigated the energy absorption properties of weft knitted structural composites under tensile, flexible, compressive and charpy impact testing conditions. In order to analyze and compare the characteristics of the energy absorption and their differences among different weft knitted structural composites, the testing was carried out in the both warp and weft directions for the composites made by parallel laid-up method and in the weft direction for the composites made by vertical laid-up method. The comparison was also done for the energy absorption properties under tensile, flexible, compressive and hung striking bar impact testing conditions. The results have shown that: 1. the derived jersey composites have the best mechanical and energy absorption properties; 2. the interlock composites are in second position, however, their energy-absorption properties under charpy impact are better than those of derived jersey composites; 3. the other composites such as rib, Milano, derived cardigan and spacer structural composites have similar properties. The results have also shown that the energy absorption properties depend on the fiber volume fraction. It is possible to increase the energy absorption properties of the composites by increasing their fiber volume fractions. Furthermore, the fiber volume fraction is connected with knitted structure, laid-up method and forming process.The results of this work will deepen the understanding of the energy absorption properties of the weft knitted structural composites and have some reference value for their practical application.