Shear response of carbon fiber composite octet-truss lattice structures

Ultralight three dimensional space filling octet-truss lattice structures have been fabricated from carbon fiber reinforced polymer (CFRP) laminates using a mechanical snap-fitting and adhesive bonding technique. The lattice structures moduli and strengths have been measured during (0 0 1) in-plane shear as a function of the lattice relative density (ρ¯). Their strength was determined by the activation of two strut failure modes: elastic buckling of the struts governed the response when ρ¯<5%, while delamination failure controlled the strength for 16%>ρ¯>5%. The measured shear strengths are shown to be well predicted by micromechanics models based on the elastic buckling and delamination failure of the struts. Snap-fit CFRP octet-truss lattice structures with densities of 24-230 kg m−3 are found to have mechanical properties superior to polymer and metal foams, and are competitive with Balsa wood and recently reported Ti-6Al-4V octet-truss lattices. They provide new opportunities for ultra-lightweight multi-axially loaded structures.