Eur. Phys. J. E (2015) 38: 95
https://doi.org/10.1140/epje/i2015-15095-2

Regular Article

A mechanical model of overnight hair curling

¹ ICAM, SV Laboratory, School of Aerospace, Xi’an Jiaotong University, 710049, Xi’an, China
² Columbia Nanomechanics Research Center, Department of Earth and Environmental Engineering, Columbia University, 10027, New York, NY, USA

^* e-mail: xichen@columbia.edu

Received: 4 March 2015
Revised: 26 June 2015
Accepted: 5 August 2015
Published online: 7 September 2015

Abstract

Based on the observation of overnight hair curling procedure, we establish a mechanical model to describe the temporary wave formation of straight hair (initial curvature is zero), which incorporates the contact between hair and hair roller. Systematic studies are carried out to explore the effects of radius ratio between hair and hair roller, hair’s average axial strain, creep time, Poisson’s ratio and gravity on the curl retention. The variation of curl retention with respect to time obtained from our numerical model is validated by a simple theoretical model and by overnight curling experiments on hair samples. The results of simulation show that overnight hair curling is suitable to create a wavy hairstyle within about 7 hours, while the combined usage with hair fixatives enables a wavy hairstyle with desired curvature that lasts for a day or more.