Effect of carbon nanofiber concentration on mechanical properties of porous magnesium composites: Experimental and theoretical analysis

This study investigated the effect of the reinforcing phase - carbon nanofiber (CNF) concentration on mechanical properties of fabricated porous magnesium-matrix composites with 34% porosity. The average yield strength and the average ultimate compressive strength increased steeply when the CNF concentration increased from 0.05% to 0.2%, and increased gradually when the CNF concentration increased from 0.2% to 1.5% and from 2% to 5%. The mechanical properties of porous magnesium-matrix composite with 1.5% CNF are the highest among the studied composites, and the average yield strength, the average ultimate compressive strength, and the energy absorption capability were enhanced by 54%, 49%, and 43% respectively from those for porous magnesium without CNF. The Rule of mixture model, Strengthening factor model, and Zhang & Chen model provided the yield strength predictions that match well with the experimental data for the composites with less than 2% CNF, and the strengthening mechanism includes Orowan strengthening and thermal expansion coefficient mismatch strengthening. The Shear Lag model and Rule of mixture model provided the yield strength predictions that match well with the experimental data for the composites with more than 2% CNF, and load transfer from magnesium to CNF is the dominating strengthening factor.