Strengthening and toughening mechanisms in graphene-Al nanolaminated composite micro-pillars

Uniaxial compression tests were carried out on micro-pillars fabricated from nanolaminated graphene (reduced graphene oxide, RGO)-Al composites of different RGO concentrations and laminate orientations (the angle between laminate planes and the pillar axis). It was found that the strengthening capability of RGO can be enhanced by either orienting the RGO layers parallel with the loading direction or raising the RGO concentration. The stress-strain response of the micro-pillars was populated with discrete bursts, and the stress increments of the bursts scaled with the RGO concentration, regardless of the laminate orientation relative to the loading direction. These observations were interpreted by the variation in the load-bearing capacity of RGO in different laminate orientations, the dislocation annihilation at the RGO/ Al interface, and a crack deflection mechanism provided by the robust RGO/AI interface that toughened the composites. This work underscores the importance of structural design and control in the stiffening, strengthening, and toughening of metal matrix composites, and the methodology developed may be applied to other composites with microstructural heterogeneity to probe their specific mechanical behaviors and structure-property correlations. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.