A new stiffness-sensing test to measure damage evolution in solids

Yichi Song,Vito L Tagarielli,Doneill J Magmanlac

doi:10.1038/s41598-021-04452-9

Yichi Song, Vito L Tagarielli + Show 1 more

Open Access

https://doi.org/10.1038/s41598-021-04452-9

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Journal: Scientific Reports	Publication Date: Jan 10, 2022
Citations: 2	License type: open-access

Affiliation: Imperial College London

Abstract

We propose and assess a procedure to measure the damage evolution in solids as a function of the applied strain, by conducting stiffness-sensing mechanical tests. These tests consist in superimposing to a monotonically increasing applied strain numerous, low-amplitude unloading/reloading cycles, and extracting the current stiffness of the specimens from the slope of the stress–strain curve in each of the unloading/reloading cycles. The technique is applied to a set of polymeric and metallic solids with a wide range of stiffness, including CFRP laminates loaded through the thickness, epoxy resins, injection-moulded and 3D printed PLA and sintered Ti powders. The tests reveal that, for all the materials tested, damage starts developing at the very early stages of deformation, during what is commonly considered an elastic response. We show that the test method is effective and allows enriching the data extracted from conventional mechanical tests, for potential use in data-driven constitutive models. We also show that the measurements are consistent with the results of acoustic and resistive measurements, and that the method can be used to quantify the viscous response of the materials tested.

Highlights

We propose and assess a procedure to measure the damage evolution in solids as a function of the applied strain, by conducting stiffness-sensing mechanical tests
We propose an extension of the Continuous Stiffness Measurement (CSM) method to uniaxial mechanical tests, resulting in a mechanical, nearcontinuous stiffness-sensing technique that can be used with conventional test machines; the method is applicable to multiaxial and/or non-monotonic tests
The stress–strain curves presented in Fig. 8 for the Carbon fibre reinforced polymer (CFRP) specimens and the neat epoxy are in line with the monotonic measurements published in18–20, indicating that the unloading/reloading cycles imposed in this study do not notably alter the measured stress–strain response of the materials

Summary

Introduction

We propose and assess a procedure to measure the damage evolution in solids as a function of the applied strain, by conducting stiffness-sensing mechanical tests. We note that in both types of tests the strain rate during the unloading and reloading phase were equal, in consideration of the relatively small change in stiffness of the specimen, which will be shown below.

Results

Conclusion