Micromechanical damage analysis of Al-Al2O3 composites via cold-spray additive manufacturing

3D micro-scale finite element (FE) models were developed to analyze the stress-state-dependent initiation and growth of failure of cold-sprayed additively manufactured (CSAM) Al-Al2O3 composites. Informed by experimental particle size distributions and porosity measurements, representative volume elements (RVEs) were generated by Digimat. Stress-state-dependent constitutive models for the Al matrix and Al2O3 ceramic particles were implemented by VUMAT subroutines in ABAQUS/Explicit FE solver. For the first time in the literature on metal-ceramic composites, the microscale failure mechanisms involving matrix ductile failure, particle cracking, and matrix/particle debonding were all quantified based on the crack volume fraction, the fraction of cracked particles, and the fraction of fully debonded interfacial nodes, respectively. The FE model was quantitatively and qualitatively validated by the experimental data for Al-46 wt% Al2O3 under quasi-static uniaxial compression. The validated model was used to investigate the effect of the particle content and size on the material behavior subjected to different stress states. The results revealed that the failure mechanisms are activated in a specified order across different stress states: I. matrix/particle debonding, II. particle cracking, and III. matrix ductile failure. The material ductility observed under compression/shear vanishes under tension due to the earlier activation of debonding and the faster growth (& SIM; 10 times) of the particle cracking mechanism. Additionally, it was shown that the particle size minimally affects the material strength and flow stress under shear which is likely related to the low load transfer effect through the interfaces. The novelty of this work stems from the provision of a better understanding of the stress-state-dependent evolution of failure mechanisms through a systematic quantification framework whose outcomes have implications for the design of better-performing Al-Al2O3 composites via control of the evolution of failure mechanisms and developing micromechanism-based constitutive models for CSAM metal-ceramic materials.

Automated summary

3D micro-scale finite element models were developed to analyze the failure mechanisms and behavior of CSAM Al-Al2O3 composites under different stress states. The models quantified the matrix ductile failure, particle cracking, and matrix/particle debonding mechanisms based on crack volume fraction, fraction of cracked particles, and fraction of debonded interfacial nodes. The models were validated and used to study the effects of particle content and size on material behavior. The results showed that the failure mechanisms are activated in a specific order and that particle size minimally affects the material strength and flow stress under shear. This work provides a better understanding of the stress-state-dependent evolution of failure mechanisms and has implications for the design of improved Al-Al2O3 composites.