A laser projection system for polymer transverse strain measurements in tensile testing

TL;DR

This paper introduces a low-cost, mobile laser projection system for precise transverse strain measurement in polymers during tensile testing, enabling detailed stress-strain analysis.

Contribution

The paper presents a novel optical system combining laser diodes, CCD detectors, and open-source signal processing for accurate polymer deformation measurement.

Findings

Detected diameter changes with 10-micrometre resolution

Successfully obtained stress-strain curves from optical measurements

System is easily mountable on tensile testing machines

Abstract

A self-built laser projection system for optical transverse strain measurements in tensile testing is presented. The setup based on laser diode modules, CCD (Charge-Coupled Device) array detectors, and standard optomechanical components is proposed to be a low-cost system for testing polymer samples. The optical setup is mobile and can easily be mounted on a tensile test machine. Circular cross-sectional changes in polymer diameter were detected with ten-micrometre resolution and stress-strain curves obtained by a tensile test machine. The article describes signal processing using the open-source programming language R, and the transverse deformation of the polymer sample is evaluated in two perpendicular planes. The results obtained by the optical system may be used to accurately describe the models of energy-based mechanical properties of polymers for complex load conditions.