Investigation On The Impact Properties Of2-D Triaxial Braid-hybrid Laminated Composites

With the increasing application of composites in aerospace and other fields, weneed to overcome the limitation of impact properties of single-kind fiber reinforcedcomposites. So hybrid composites have broad prospects for future development.Current researches about low velocity impact and post-impact properties of braidlaminated composites are relatively few, but mostly focus on the mechanicalproperties of single-layer braiding and unidirectional laminated composites. So thisproject mainly did experimental studies and theoretical analysis on impact propertiesand bending properties after impact of2D triaxial braid hybrid laminated composites,thus providing references for application design about impact properties of braidhybrid laminated composites.In this paper, two main type structures including seven kinds of composites wereinvestigated. The first type structure contains four kinds of composites, respectivelyas following: laminated through three layers braided with carbon fiber; laminatedthrough upper and lower layers braided with carbon fiber and middle layer braidedwith glass fiber; laminated through upper and lower layers braided with glass fiberand middle layer braided with carbon fiber; laminated through three layers braidedwith glass fiber. The second type structure contains three kinds of composites,respectively as following: laminated through three layers braided with carbon fiber asbraiding yarn and glass fiber as axial yarn; laminated through three layers braided with glass fiber as braiding yarn and carbon fiber as axial yarn; laminated throughthree layers braided with hybrid arrangement of carbon fiber and glass fiber asbraiding yarn and axial yarn.In this paper, we use the drop hammer impact test and three-point bending testfor the comprehensive mechanical properties, digital cameras to observe thedistribution of surface damage, and stereo microscope to observe the cross-sectionaland longitudinal section features. We can preliminary conclude the impact resistanceof composites through damage disciplines and data contras, and bending propertiesthrough bending tests, and then compared with post impact bending properties toanalyze which kind of composite had better residual flexural properties. Thus we canconclude better composite specimens with optimum impact resistance properties.Composites laminated through upper and lower layers braided with carbon fiberand middle layer braided with glass fiber, compared with composites laminatedthrough three layers braided with carbon fiber, the former had fewer cracks on bothsurfaces after impact, fewer cracks on the cross-section at the center of impact,7.61%higher on energy absorption per unit thickness,16.46%higher on maximum bendingload,19.52%higher on flexural strength, but40.60%lower on loss rate of flexuralstrength after impact. Therefore, three braid-layers composites laminated throughouter layers braided with rigid material and middle layer braided with ductile material,can effectively improve the impact properties of hybrid composites.Composites laminated through upper and lower layers braided with glass fiberand middle layer braided with carbon fiber, compared with composites laminatedthrough three layers braided with glass fiber, the former had fewer cracks on bothsurfaces after impact, fewer cracks on the cross-section at the center of impact,2.21%higher on energy absorption per unit thickness,2.12%higher on maximum bendingload,11.46%higher on flexural strength, but5.30%higher on loss rate of flexuralstrength after impact. Therefore, three braid-layers composites laminated throughouter layers braided with ductile material and middle layer braided with rigid material,can improve the impact properties of hybrid composites in little extent. Composites laminated through three layers braided with carbon fiber as braidingyarn and glass fiber as axial yarn, compared with composites laminated through threelayers braided with glass fiber as braiding yarn and carbon fiber as axial yarn, theformer had more cracks on impact surface, fewer cracks on back surface after impact,more cracks on the cross-section at the center of impact,25.80%higher on energyabsorption per unit thickness,18.64%higher on maximum bending load,15.25%higher on flexural strength, but98.83%higher on loss rate of flexural strength afterimpact. Therefore, three braid-layers composites laminated through outer layersbraided with ductile material and middle layer braided with rigid material, canimprove the impact properties of hybrid composites in litter extent.Composites laminated through three layers braided with hybrid arrangement ofcarbon fiber and glass fiber as braiding yarn and axial yarn, had the most cracks onboth surfaces after impact, the fewest cracks on the cross-section at the center ofimpact, the lest energy absorption per unit thickness, the least maximum bending load,the least flexural strength, but less loss rate of flexural strength after impact.Therefore, each layer of braid laminate composites braided with hybrid of rigidmaterial and ductile material, can make the impact properties decreased. However,Composites laminated through three layers braided with ductile material as braidingyarn and rigid material as axial yarn have better delamination resistance performance.Three braid-layer composites laminated through outer layers braided with ductilematerial and middle layer braided with rigid material, can improve the impactproperties of hybrid composites in great extent. Three braid-layer compositeslaminated through outer layers braided with ductile material and middle layer braidedwith rigid material, can improve the impact properties of hybrid composites in littleextent. Each layer of braid laminate composites braided with hybrid of rigid materialand ductile material, can make the impact properties decreased. However, compositeslaminated through three layers braided with ductile material as braiding yarn and rigidmaterial as axial yarn have better delamination resistance performance.