Interlaminar shear properties of composites with Ni-Cr alloy weft knitted electric heating layer
Objective In order to ensure the helicopter can operate safely in all weather,especially at low temperature,the engine inlet anti-icing protection is necessary.Therefore,it is of great significance to develop electrothermal composites that can not only meet the requirements of lightweight helicopter inlet structure,but also realize the heating function.Due to the structural complexity of the multi curvature of the helicopter inlet,a glass filer/epoxy laminated composite with integrated structure and function is developed based on the weft knitted fabric with excellent formability performance.Method Three kinds of nickel chromium alloy wires of different fineness are selected to design and prepare 9 kinds of fabrics with three kinds of weave structures:plain,rib and interlock.Based on the principle of minimum thickness,six kinds of weft knitted electrically heated fabrics were selected.The glass filer/epoxy laminated composite was prepared by using nickel chromium alloy weft knitted fabric as the intermediate electric heating layer and the autoclave composite molding process was preferred.The electrothermal properties and interlaminar shear properties of the composites were tested by infrared thermography and universal testing machine.Results The results showed that under 8 V direct current(DC)voltage,the temperature of the six kinds of electrothermal composites can rise above 37 ℃,up to 72 ℃,taking 30 s,and the heating rate can reach 1.58 ℃/s.The composites showed that the maximum equilibrium temperature is positively related to the fineness of Ni-Cr alloy wire.Under 8 V DC voltage,the maximum equilibrium temperature of plain composite samples with nickel chromium alloy wire fineness of 0.08 mm,0.06 mm and 0.04 mm in 30 s is 72.8 ℃,67.1 ℃ and 49.0 ℃ respectively.Compared with rib and interlock,the maximum equilibrium temperature of plain structure composite is the highest.Based on the fineness diameter of nickel chromium alloy wire is 0.04 mm,the maximum equilibrium temperature of plain,rib and interlock electrothermal composite samples reached in 30 s is 49.0 ℃,37.2 ℃ and 45.7 ℃ respectively.The electric heating surface temperature of the six electric heating composite materials is evenly distributed,and the temperature difference is within 7 ℃.The surface temperature uniformity of interlock composite is better than that of plain and rib composites,and the surface temperature difference is only 3 ℃.The interlaminar shear strength of glass/epoxy laminated composite without electric heating layer is 74.18 MPa.The interlaminar shear strengths of the longitudinal and transverse specimens of the electrothermal composite materials are higher than 54.97 MPa and 63.01 MPa,respectively.The retention rate of interlaminar shear strength of electrothermal composites is about 74％-97％compared with that of composites without electrothermal layer.The damage morphology of composite sample after was analyzed.According to the analysis of the damage morphology of the electrothermal samples after interlaminar shear test,the longitudinal and transverse shear samples mainly failed because of the bending failure of the outermost prepreg on the lower surface,and a little interface delamination occurred in the middle layer due to the shear failure,but the structure of electrothermal weft knitted reinforced fabric was not damaged.Conclusion The preliminary research work shows that the glass filer/epoxy laminated composite material with nickel chromium alloy wire weft knitted fabric as the intermediate electric heating layer prepared by the autoclave composite molding process can achieve both the electric heating function and the bearing mechanical properties of the composite material at the same time,which is expected to meet the design requirements of the helicopter engine inlet anti-icing/deicing system.In addition,it broadens the application range of weft knitted fabric,and also provides a new way for the diversification of the composite electric heating layer used for electric anti-icing,which has the significance of engineering practical application.
万方数据
维普
