Fracture mechanics of micro samples: Fundamental considerations

TL;DR

This review explores how fracture mechanics principles apply to micro and nanometer-sized samples, addressing challenges in testing, interpretation, and understanding crack growth at small scales for better device reliability.

Contribution

It provides a comprehensive analysis of fracture mechanics at micro and nano scales, including scaling laws, testing procedures, and new experimental possibilities.

Findings

Scaling considerations are crucial for micro and nanomechanics.

Specimen size influences crack growth resistance measurements.

Novel testing methods can enhance understanding of crack propagation.

Abstract

In this review article we consider the crack growth resistance ofmicrometer and submicrometer sized samples from the fracture mechanics point of view. Standard fracture mechanics test procedures were developed for macroscale samples, and reduction of the specimen dimensions by three to five orders of magnitude has severe consequences. This concerns the interpretation of results obtained by micro and nanomechanics, as well as the life time and failure prediction of micro and nano devices. We discuss the relevant fracture mechanics length scales and their relation to the material specific structural lengths in order to conduct rigorous fracture mechanics experiments. To ensure general validity and applicability of evaluation concepts, these scaling considerations are detailed for ideally brittle, semi brittle and micro ductile crack propagation, subject to both monotonic and cyclic loading. Special attention is devoted to the requirements for determining specimen size for various loading types to measure material characteristic crack propagation resistance at small scales. Finally, we discuss novel possibilities of micron and submicron fracture mechanics tests to improve the basic understanding of specific crack propagation processes.