Study On Mechanical Properties Of Carbon-aramid Fiber-titanium Super-hybrid Three-dimensional Braided Composites

Composites containing metal fibre or metal layer and reinforcing the same matrix together with non-metallic fibre are called super-hybrid composites.In order to improve the toughness of carbon fibre reinforced plastics(CFRP),four kinds of super-hybrid three-dimensional five-directional braided composites with carbon fibre,aramid fibre and titanium wire were designed and prepared,respectively.Including carbon fibre as axle yarn,and carbon-Ti co-hybrid and aramid-Ti co-hybrid as braiding yarn,and carbon-Ti co-hybrid as axle yarn,aramid fibre as braiding yarn.Firstly,TA2-0.05-W and TA2-0.05-B titanium wires were selected by tensile and wetting properties from three kinds of titanium wires.Secondly,the cross-section morphologies of the composites were observed.The results show that the blended fibre has a significant effect on the axle yarn.The axle yarn of carbon-aramid-Ti super-hybrid composites presents isosceles triangle or fan-shaped,while that of CFRP is fan-shaped.Finally,the axial tensile properties,axial bending properties,transverse short beam shear properties and axial lzod impact properties of the super-hybrid composites were tested respectively.The effects of different blended fibres and blended methods on the mechanical properties of the super-hybrid composites were discussed by analyzing the failure morphologies of the specimens.The results show that the axial tensile properties of the composites are mainly related to the axial yarn.The tensile strength and modulus of aramid fibre as braiding yarn,and carbon-Ti co-hybrid as axial yarn are 15.2%and-1.3%higher than those of aramid-Ti co-hybrid as braiding yarn,and carbon fibre as axial yarn.The fracture morphologies show that the aramid fibre in the super-hybrid composites presents ductile fracture characteristics.The results of axial bending test show that the deflection at the maximum load of aramid-Ti co-hybrid and aramid fibre as braiding yarn is 60.9%and 47.8%higher than CFRP,respectively.The fracture morphologies show that the titanium wire obviously blocks the crack propagation and the damage degree is lower than CFRP.When TA2-0.05-W and TA2-0.05-B titanium wires were added,the shear strength of short beam decreases by 5.4%and 10.7%respectively compared with CFRP,which reflects the decrease of interfacial properties between fibre bundles and epoxy resin.The axial lzod impact strength of aramid-Ti co-hybrid and aramid fibre as braiding yarn is 7.8%and 0.7%higher than CFRP.In addition,in view of the weak interfacial properties between titanium wire and epoxy resin,a method was provided to improve the interfacial shear strength between titanium wire and epoxy resin–atmospheric plasma treatment.When the plasma treatment time is 40 s,the scanning speed is 2 mm/s,and the working gas flow rate is15 L/min Ar/0.30 L/min 0₂,the interfacial shear strength between titanium wire and epoxy resin is 189%higher than that of untreated.In conclusion,through the observation of mechanical properties and failure morphologies,it can be seen that the addition of aramid fibre and titanium wire significantly improves the fracture toughness and safety of CFRP.