Inverse determination of delamination shape and size in self-sensing composites using electrical impedance tomography and genetic algorithms

Abstract

Fiber-reinforced composites with nanofiller-modified polymer matrices have immense potential to improve the safety of high-risk engineering structures. These materials are intrinsically self-sensing because their electrical conductivity is affected by deformations and damage. This property, known as piezoresistivity, has been extensively leveraged for conductivity-based damage detection via electrical resistance change methods and tomographic imaging techniques such as electrical impedance tomography (EIT). Although these techniques are very effective at detecting the presence of damage, they suffer from an inability to provide precise information about damage shape, size, or mechanism. This is particularly detrimental for laminated composites which can suffer from complex failure modes, such as delaminations, that are difficult to detect. To that end, we herein propose a new technique for precisely determining damage shape and size in self-sensing composites. Our technique makes use of a genetic algorithm (GA) integrated with realistic physics-based damage models to recover precise damage shape from conductivity changes imaged via EIT. We experimentally validate this technique on carbon nanofiber (CNF)-modified glass fiber-reinforced polymer (GFRP) laminates by considering two specific damage mechanisms: through-holes and delaminations. Our results show that this novel technique can accurately reconstruct multiple through-holes with radii as small as 1.19 mm and delaminations caused by low velocity impacts. These findings illustrate that coupling piezoresistivity with conductivity-based spatial imaging techniques and physics-based inversion strategies can enable damage shaping capabilities in self-sensing composite structures.

Structural engineering from an inverse problems perspective

“…needing only to predict hole number, radius and inplane coordinates). As a final example, a recent study looked at delamination shaping from EIT images in CNF-modified glass fibre/epoxy laminates [285]. In this study, delaminations induced by low-velocity impacts were parameterized as ellipses of unknown major and minor axes and centred at unknown in-plane coordinates.…”

Structural engineering from an inverse problems perspective

“…Real damages are obviously much more complex than simple through-holes. As a final example of damage recovery, a recent study looked at delamination shaping from EIT images in CNF-modified glass fibre/epoxy laminates [288]. In this study, delaminations (i.e.…”