Citation: Mieloszyk, M.; Majewska,
K.; Andrearczyk, A. Embedded
Optical Fibre with Fibre Bragg
Grating Influence on Additive
Manufactured Polymeric Structure
Durability. Materials 2022, 15, 2653.
https://doi.org/10.3390/
ma15072653
Academic Editor: Juergen Stampfl
Received: 25 February 2022
Accepted: 30 March 2022
Published: 4 April 2022
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Article
Embedded Optical Fibre with Fibre Bragg Grating Influence on
Additive Manufactured Polymeric Structure Durability
Magdalena Mieloszyk * , Katarzyna Majewska and Artur Andrearczyk
Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdansk, Poland;
k.majewska@imp.gda.pl (K.M.); aandrearczyk@imp.gda.pl (A.A.)
* Correspondence: mmieloszyk@imp.gda.pl
Abstract:
Additive manufacturing (AM) polymers are applied in many branches of the industry due
to the possibility of fast and accurate production of elements with various and complex shapes. Fibre
Bragg grating sensors (FBG) are widely applied in structural health monitoring (SHM) systems. The
main objective of this research is to perform analyses of the influence of embedded FBG sensors on
AM polymer elements’ durability. Two polymers (M3 X and M3 Crystal) with different mechanical
properties were analysed. The tests were performed on samples with FBG sensors embedded
in (different alignment) and attached to the surfaces of the elements. Firstly, the samples were
exposed to elevated or sub-zero temperatures under stable relative humidity levels. The strain in
the samples was measured using fibre Bragg grating (FBG) sensors. The achieved results allow us to
determine the relationships between strain and temperature for both materials and the differences
in their mechanical response to the thermal loading. Then, the samples were subjected to a tensile
test. A comparison of the tensile strength values was performed for the samples without and with
embedded FBG sensors. The samples after the tensile tests were compared, showing differences
in the mechanisms of failures related to the polymers and the thermal treatment influence on the
material internal structure. Additionally, strain values measured by the FBG sensors were compared
to the strain values achieved from the testing machine showing a good agreement (especially for M3
X) and indicating the differences in the materials’ mechanical properties. The achieved results allow
us to conclude there is a lack of influence of embedded FBG sensors on the mechanical durability of
AM polymers.
Keywords: additive manufacturing; polymer; fibre Bragg grating sensor; tensile strength
1. Introduction
Additive manufacturing (AM) techniques are recently very popular in many
branches of industry due to the possibility of fast and accurate production of elements with
various and complex shapes [
1
]. Among many materials, polymers have been recently
widely applied [
2
] as they allow manufacturing structures both for everyday use and
technical elements for testing prototypic solutions [
3
]. The variety of applications of AM
elements causes them to be exposed to different mechanical loadings and environmental
factors. The mechanical properties of AM samples are affected by both the unprinted
material properties and the manufacturing process parameters. Among others, mechanical
anisotropy being a result of the manufacturing process characteristic is the largest problem
in AM elements [4].
There are a variety of optical materials that can serve as sensors for different physical
or chemical parameters. One of the groups of materials is insulating materials that are
commonly used for optical lenses or optical waveguides (optical fibres in telecommuni-
cation) [
5
]. Fibre Bragg gratings (FBG) can be inscribed in photosensitive fibres in almost
any type of optical fibres, including silica core fibres and sapphire fibres [
6
]. The standard
Bragg gratings written in silica core optical fibres are the most common and are applied as
Materials 2022, 15 , 2653. https://doi.org/10.3390/ma15072653 https://www.mdpi.com/journal/materials
