Shear Band Formation in Thin-Film Multilayer Columns Under Compressive Loading: A Mechanistic Study

Area of Science:

• Materials Science
• Mechanical Engineering
• Solid Mechanics

Background:

• Micro-pillar compression is a key technique for analyzing nano- and micro-laminates.
• Experimental studies often observe plastic instability, specifically shear bands, leading to failure.
• Understanding shear band formation is crucial for predicting material performance.

Purpose of the Study:

• To computationally investigate the commonality of shear band formation in micro-pillar compression from a continuum mechanics perspective.
• To correlate numerical findings with experimental observations of deformation and damage.
• To explore factors influencing shear band development.

Main Methods:

• Systematic finite element analyses (FEA) were performed on column-shaped thin-film composites.
• The study focused on simulating the compressive stress-strain response and strain field evolution.
• Numerical models were used to visualize shear offsets and compare with experimental microscopy.

Main Results:

• FEA demonstrated strain localization once plastic yielding initiated.
• Numerical models successfully replicated distinct shear offsets observed in experiments.
• Material constitutive behavior (strain hardening/softening) and geometric imperfections significantly impacted shear band formation.

Conclusions:

• Shear band formation is an inherent outcome of plastic yielding in micro-pillar compression, predictable via continuum modeling.
• Material properties and geometric details critically govern the morphology and occurrence of shear bands.
• Computational approaches provide valuable insights into the mechanisms underlying laminate failure.