Preparation And Stab-resistant Mechanism Study Of Composite Scales For Semi-hard Stab-resistant Fabric

As a significant kind of personnel protection,stab-resistant fabrics have attracted more and more attentions,especially the ones based on fibers.Among the fiber-based stab-resistant fabrics,semi-hard stab-resistant fabrics consisting of flexible base cloth and rigid scales present excellent stab resistance performances but high flexibility and,thus,have been used widely.Even so,the researches relevant to semi-hard stab-resistant fabrics remain few.In the current thesis,the fiber reinforced composite scales for semi-hard stab-resistant fabrics have been fabricated based on multilayer stab-resistant fabrics coated by B₄C hard particles and infused by epoxy resin,the scale shape and arrangement on the base cloth have been optimized,while the stab-resistant mechanism of the scales has also been investigated.The results shown in the current thesis could be useful for the design and preparation of semi-hard stab-resistant fabrics,with better stab resistance,higher flexibility and lighter weight.?1?Preparation of B₄C coated fabrics.By the orthogonal tests of three factors and four levels,the optimum dispersing solution for the preparation of B₄C hard particles was determined:particle diameter 2.5um,B₄C mass fraction 49%,and stirring temperature 30°C.B₄C coating solution was obtained by mixing uniform B₄C dispersion solution with appropriate epoxy resin adhesive.Then the coating solution was printed onto aramid fabric by screen printing.The stiffness,single-bundle pulling-out,single-tongue tearing and quasi-static puncture tests of B₄C coated fabrics were carried out to investigate the effects of the diameter and mass fraction of B₄C hard particles on the mechanical performances of coated fabric.The results show that the addition of B₄C hard particles not only improves the flexibility of coated fabrics,but also enhances the mechanical properties of coated fabrics,with the maximum puncture force per weight 486N/g,increasing by 428%.?2?Preparation of co-cured multilayer composite fabrics.B₄C coated fabrics with the best stab-resistance properties were laminated to prepare multilayer composite fabrics.During curing,an appropriate amount of B₄C hard particles with 2.5?m diameter were added into epoxy resin and the co-cured multilayer composite fabrics were prepared by vacuum assisted resin transfer molding?VARTM?.The quasi-static puncture tests showed that the maximum puncture load per weight of the woven/nonwoven/woven composite fabrics with B₄C mass fraction 2%and stacking angle 45°is increased by 269%.In addition,through the dynamic puncture tests,it was found that when the thickness of composite fabrics reached 4.48mm,consisting of 15 laminas,the penetration can be avoided totally.?3?Shape design and arrangement of composite scales.The composite fabrics were cut into composite scales and pasted onto aramid fabric,the soft base cloth.The inter-scale gap width has been optimized by studying the critical cases where the standard knife begins to contact the base cloth.The results showed that the critical gap width of the arc edge scale is 10.5%higher than that of the straight edge scale.I.e.,the arc edge scale can reduce the penetration depth under the same gap width.In addition,by combining the arc and regular hexagon scales,long gaps were avoided.?4?Stab-resistant mechanism.By analyzing the surface and fracture morphologies and the load-displacement curves of the B₄C coated fabrics and co-cured multilayer composite fabrics,stab-resistant mechanisms have been investigated.The addition of B₄C hard particles facilitates the fiber slipping and pulling-out and restrains the asynchrony of fiber breakage,while the tip and blade of the knife are passivated.The woven/nonwoven/woven co-cured multilayer composite fabrics can not only restrain the puncture of the tool tip,but also reduce the interlaminar defects.The nonwoven layer in the middle can further increase the absorption of puncture energy.Also,under the load of puncture,the soft base cloth can curve to close the inter-scale gap and make the knife grasped by adjacent composite scales,resulting in the“self-locking”effect to hinder the penetration of knife tip.Studies reported in the current thesis would be helpful to the fabrication of composite scales for semi-hard stab-resistant fabrics and be of significance to the mechanism study of hard particle coated stab-resistant textiles.