The mechanical response of ceramic microballoon reinforced aluminum matrixcomposites under compressive loading

An investigation is performed on the mechanical response of a family of cer amic microballoon reinforced aluminum matrix composites under both uniaxial compression and constrained die compression loadings. The key material par ameters that are varied are the matrix strength and the ratio of wall thick ness t to radius R of the microballoons. Uniaxial compressive failure initi ates at relatively small strains (approximate to 1-2%) and occurs through a process of crushing and collapse of the material within a localized deform ation band. Under constrained die conditions, localization is suppressed an d the flow stress increases monotonically with increasing strain. The latte r response is well described by Gurson's constitutive law for plastic yield ing of porous ductile metals, with an effective strength that depends on th e relative wall thickness, t/R. Furthermore, the energy absorption capacity (approximate to 60-70 MJ/m(3)) is extremely high in comparison with values that are typical of metal foams. The results suggest that the microballoon composites may be attractive for applications requiring a high resistance to penetration by projectiles or other forms of local intrusion, in combina tion with a high compressive strength. (C) 1999 Acta Metallurgica Inc. Publ ished by Elsevier Science Ltd. All rights reserved.