Dynamic response of additively manufactured graded foams

摘要

The dynamic responses of continuous graded foams are investigated experimentally and numerically. The Voronoi model is employed to construct foam specimens. Graded foams with different gradients and uniform foams with different relative densities are fabricated by the additive manufacturing technique. Experimental results indicate that the gradient distribution notably influences the mechanical properties of foams under a low-velocity impact (about 20 m/s). If the lowest density region is close to one end of a specimen, this end will present a gradually increasing plateau stage in the stress-strain curve. While if the highest density region is placed to one end, this end will exhibit a sharp fluctuation before the gradually increasing plateau stage. Besides, the crushing behaviors of graded and uniform foams are compared to propose an elastic, collapse, plastic hardening, densification (E-C-PH-D) constitutive model. The E-C-PH-D model can predict the dynamic mechanical properties of graded foams with successive layered deformation. A high-velocity impact (100 m/s) study is also caned out by the numerical simulation. The impact end of graded foams shows distinct higher stresses than the support end due to the shock wave effect. The combined effects of gradient and shock wave on the crushing responses of foams are discussed systematically.