Size effects in micro and nanoscale materials fracture

TL;DR

This review discusses recent experimental and computational studies on size effects in micro and nanoscale materials fracture, highlighting theories, limitations, and providing a tutorial for data analysis in this field.

Contribution

It offers a comprehensive overview of recent advances in understanding size effects in micro and nanoscale fracture, including experimental, computational, and theoretical perspectives, with a unifying framework.

Findings

Size effects are significant in micro and nanoscale fracture behavior.

Traditional extreme value theories are extended for small-scale materials.

A tutorial for analyzing fracture data at small scales is provided.

Abstract

Micro and nanoscale materials have remarkable mechanical properties, such as enhanced strength and toughness, but usually display sample-to-sample fluctuations and non-trivial size effects, a nuisance for engineering applications and an intriguing problem for science. Our understanding of size-effects in small-scale materials has progressed considerably in the past few years thanks to a growing number of experimental measurements on carbon based nanomaterials, such as graphene carbon nanotubes, and on crystalline and amorphous micro/nanopillars and micro/nanowires. At the same time, increased computational power allowed atomistic simulations to reach experimentally relevant sample sizes. From the theoretical point of view, the standard analysis and interpretation of experimental and computational data relies on traditional extreme value theories developed decades ago for macroscopic samples, with recent work extending some of the limiting assumptions of the original theories. In this review, we discuss the recent experimental and numerical literature on micro and nanoscale fracture size effects, illustrate existing theories pointing out their advantages and limitations and finally provide a tutorial for analyzing fracture data from micro and nanoscale samples. We discuss a broad spectrum of materials but provide at the same time a unifying theoretical framework that should be helpful for materials scientists working on micro and nanoscale mechanics.