Mixing effects for the mechanical properties and the fracture mechanics of an aluminum-hollow glass microspheres composite

A low density composite of hollow volcano glass microspheres and aluminum (SBAC) was prepared by filling a mold with the microspheres (SB) and forcing the molten aluminum alloy into the mold. Composite effects for the mechanical properties and fracture mechanism of the composite were examined through uniaxial compressive tests. An yielding phenomenon of the composite is attributed to fracture of the hollow microspheres. The fractured microspheres can not transmit the stress. The compressive strength is given as a mean stress at which the narrowest parts of network structure of the matrix metal are ruptured by the stress concentration caused by fracture of the microspheres. Both the apparent mean elastic modulus (ESBa) and compressive strcngth (σSBc) of the microspheres are directly proportional to the ratio of the mean radius to the mean wall thickness of the microspheres. The apparent mean elastic modulus (ESBACa)and yielding strength (σSBACc) of the composite are; ESBACa=ESBaVSBa+EMa(1-VSBa) and σSBACc=σSBcVSBa+σMc(1-VSBa) where VSBa is the volume fraction of unfractured microspheres in the composite, EMa the apparent elastic modulus of the matrix metal, and σMc the stress of the matrix metal at the yielding strain of the composite.