Quantification of microdamage phenomena during tensile straining of high volume fraction particle reinforced aluminium

Abstract

Abstract-Particle reinforced composites are produced by infiltrating ceramic particle beds with 99.99% Al. Resulting materials feature a relatively high volume fraction (40-55 vol. pct) of homogeneously distributed reinforcement. The evolution of damage during tensile straining of these composites is monitored using two indirect methods; namely by tracking changes in density and in Young's modulus. Identification and quantification of the active damage mechanisms is conducted on polished sections of failed tensile specimens; particle fracture and void formation in the matrix are the predominant damage micromechanisms in these materials. The damage parameter derived from the change in density at a given strain is found to be one to two orders of magnitude smaller than the parameter based on changes in Young's modulus. A simple micromechanical analysis inspired by the observed damage micromechanisms is used to correlate the two indirect measurements of damage. The predictions of this analysis are in good agreement with experiment.

Influence of damage on the tensile behaviour of pure aluminium reinforced with ≥40 vol. pct alumina particles

“…Quasistatic tensile tests were conducted on a screw-driven universal-testing machine using sub-sized dogbone samples [18]. Longitudinal displacements were measured with a clip-on extensometer over a 10 mm gauge length.…”

“…Longitudinal displacements were measured with a clip-on extensometer over a 10 mm gauge length. True stress-true strain curves were calculated from the load-extension data assuming volume constancy [54]; this is a valid assumption since relative volume changes in the present materials during tensile straining (due to damage accumulation) are small and on the order of 10 Ϫ3 [18]. As-cast materials and tensile samples that were loaded to failure were sectioned, polished (according to procedures outlined in [18]), and examined under an optical microscope and a scanning electron microscope (SEM).…”

“…For PRMMCs two main damage mechanisms have been reported: reinforcement fracture, and matrix voiding at or near the matrix-reinforcement interface [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Various studies have also shown that microstructural damage increases gradually with tensile deformation and is directly linked to tensile strain and/or tensile stress (e.g.…”

“…Various studies have also shown that microstructural damage increases gradually with tensile deformation and is directly linked to tensile strain and/or tensile stress (e.g. [12,[18][19][20][21][22][23][24][25][26][27][28]). Reinforcement characteristics have proven to be influential in determining the predominant damage micromechanisms and their rate of accumulation.…”

“…In a previous publication [18] we studied the accumulation of internal damage in infiltrated particle reinforced composites (Al 2 O 3 -Al and B 4 C-Al), using two damage parameters, namely D E [equation (2)] and D r (the relative decrease in density, equal to the volume fraction porosity). We showed that both damage parameters change as a function of microstructural characteristics and tensile strain, and we provided a link between their respective magnitudes and the micromechanisms of damage accumulation.…”