Thermal/Mechanical Performance Analysis Of Bio-inspired Thermal Protection Structures Manufactured By Selective Laser Melting

In this paper,based on the requirement for thermal insulation and mechanical properties of thermal protection structures in the extreme environment of the aerospace field,a series of multi-functional thermal protection structures,inspired by Norway Spruce,horsetails plants and honeycomb,was designed and manufactured by selective laser melting.The effects of bio-inspired structure design on thermal and mechanical properties were investigated through the combination of finite element analysis and experimental characterization.For the gradient structures inspired by Norway Spruce,the effects of arrangement of hollow tubes with different size on the thermal insulation and mechanical properties were studied.The temperature field simulation results showed that the gradient structure,with larger hollow tubes near the top and bottom plates and smaller hollow tubes in the center,behaved the best thermal protection performance and the lowest thermal conductivity(2.321 W/(m·K)).The compressive tests revealed that the above structure also exhibited the best bearing and energy absorption capacity,whose specific energy absorption and specific strength were 29.3 % and 4.22 % higher than that of the no gradient structure,respectively.To further enhance compressive properties of bio-inspired structures,horsetail plants were chosen as the bionic object and new bio-inspired hollow-tube structures with inner tube were designed.The influence of inner tube diameter on the thermal insulation ability and bearing capacity was investigated.The research results showed that the introduction of inner tube structures reduced the thermal insulation ability of the bio-inspired structures,however,improved the compressive strength of structures.Besides,the compressive strength decreased with the increasing of the inner tube diameter,the samples with the inner tube diameter of 2.4 mm exhibited the best bearing and energy absorption,whose energy absorption and specific energy absorption were 55.6 J and 3.3 J/g,respectively.The honeycomb structure,as a traditional hollow thin-walled structure,has good axial bearing capacity.To further improve the thermal protection performance,novel honeycomb structures with twist feature along axial direction were designed and the influence of twist angle on the thermal insulation and bearing capacity quantitatively was investigated.Temperature field simulation results showed that the heat transfer path extended with the increase of twist angel,which improved the thermal insulation performance of structures.Compressive test results indicated that the honeycomb structure exhibited the best bearing ability when the twist angle was 30°.Comparing with the honeycomb structures without twist feature,the specific compressive strength and specific energy absorption of the twisted honeycomb structure of 30° angle increased by 27.0 % and 27.8 %,respectively.