Preparaton And Mechanical Properties Of Improved Pyramid Lattice Trus Structure

In recent years, along with the rapid development of the aviation and aerospacetechnologies, a new type of aerospace structure with lightweight and multifunctionalitycharacteristics is needed. However, the examples for the traditional aerospace structure,sandwich structures with honeycomb or cellular foam core have been unable to meet thisneeds, a new type of sandwich structure with lattice core has been proposed. Researchshows that the lattice sandwich structure has become a new generation structure for itsowing to lighter weight, super strong and ductile, and other multifunctionality. Thepyramidal lattice structure is investigated to date have been fabricated from metal bondingusing brazing or laser welding. Carbon fiber reinforced polymer composites have an evenhigher specific strength than the light alloys and have been utilized as facesheet materials insandwich panels for demanding high strength applications. However due fabricationchallenges, CFRP composites have not been widely used for the lattice truss cores.In present paper, a new fabrication method is proposed, in which, by increasing areinforced bar at the nodes of structure, the interplay adhesive areas between the face sheetand pyramidal truss core is increased, in other words, change the'point'bonds intothe'line'bonds between the face sheet and core of structure, subsequently, the adhesivebonding strength of face sheet and cores are dramatically improved. A new mould has beendesigned in order to fabricate the new pyramidal truss cores specimens. Carbon fibercomposite pyramidal truss cores with two different relative densities 1.48% and 2.85%were made. Experimental tests including out-of plane compression, shear, in-planecompression and three point bending loads have been conducted. Analytical models forpredicting the failure load associated with each mode are also presented. Results show thatdifferent failure modes of the pyramidal truss cores sandwich panels are revealed. Corefailure occurred by either (ⅰ) Euler buckling (1.48%) or (ⅱ) node fracture (2.85%) under outof plane compression. Node delamination is the dominated failure of present sandwichpanels under shear and three point bending. The core shear buckling of structures areobserved under in plane compression. The fabricated low density truss cores basing on newmethod increasing face/core bonding area have avoided effectively the face/core debondingfailure and have improved overall performance of the pyramidal lattice sandwich structure.