Study On Thermal/Mechanical Properties Of Composite Anti-icing Functional Unit

With an increasing use of composite materials in civil aircraft design engineering,composite components' anti-icing problems is receiving people's concern.Composite electro-thermal anti-icing structure with embedded electric heating elements is an effective method to solve composites' anti-icing problems.When anti-icing system works,it will cause a large temperature gradient in composite materials which could affect thermal/mechanical properties of each layer's materials.In this paper,a combination of numerical simulation and experiment is used to study thermal/mechanical properties of composite anti-icing functional unit at a very early stage.Main works are as follows:(1)The current status of research on aircraft anti-icing technology and thermal/mechanical properties of composite laminate structure at home and abroad is briefly introduced.And the necessity of research in this paper is pointed out.(2)A section on leading edge slat of ARJ-21 aircraft is been selected as the functional unit calculation model.And the electric heating heat flux density is designed by using anti-icing thermal load calculation method,which provides a basis for design of heating elements' structure on the electric heating layer.(3)Based on numerical simulation methods,the composite electro-thermal anti-icing structure with embedded electric heating elements is designed and it meets strength requirements of aircrafts.The composite electro-thermal plate structure is constructed,and metal films' arrangements' influence of electric heating layer on structural's temperature field and thermal stress distributions is investigated.Results show when the gap between metal films increases,the temperature of corresponding area on anti-icing surface decreases,and the stress of electric heating layer near the gap is lower than that away from the gap.Also,based on the designed heat flux density,temperature field and thermal stress distributions of composite anti-icing functional unit are numerically simulated.Results show that the heat flux density and electric heating structure designed in this paper meets anti-icing requirements when used for functional unit's anti-icing.(4)Thermal/ mechanical experiments of the composite anti-icing functional unit is carried out in this paper to investigate changes in performance of functional unit test pieces when subjected to loads.Results show that when the fatigue load amplitude is taken at 30% of the uniaxial tensile failure load,the test pieces didn't result in failure of function,but when taking at 60% and 73%,the test pieces resulted in failure of function.Last but not not least,due to particularities of thermal spraying process,the metal film on electric heating layer is a discontinuous phase and there is no complete resilience period,so it cannot be restored to the initial resistance value after being subjected to loads.