This study investigates the tensile behaviour of basalt fibre reinforced polymer (BFRP) composites that were developed using braiding as a manufacturing technique. Those materials will be introduced in concrete reinforcement applications. Three BFRP rebar sizes with a circular constant cross section and different braided configurations are developed and characterised with respect to their internal architecture. The braid angle on each layer of the rebar, varying from 10◦ to 45◦, is an important parameter that has a direct impact on its performance characteristics. The effective longitudinal in-plane modulus (ExFRP) of each braided sample is calculated numerically using the classical laminate theory (CLT) approach and then, tensile tests are performed according to the relevant standard. Comparisons between analytical and experimental data demonstrate a significant influence of braiding parameters, like braiding angle and number of braiding layers, on the mechanical properties of BFRP rebars. In addition, it is noteworthy that all predicted moduli determined with CLT numerical approach are found to be higher than the test results and overestimate rebar’s stiffness, most probably due to the degree of undulation from braiding process.

1. Reducing Uncertainty in Structural Safety
Special Session SS6
Ghent, Belgium
28-31 October 2018

2. Sofia Antonopoulou, Ciaran McNally and Greg Byrne
Mechanical characterisation of
braided BFRP rebars for internal
concrete reinforcement

3. Research Idea
Aim of the project:
Main goal:
Design, Development & Characterisation of Basalt Fibre
Reinforced Polymer composites, for internal concrete
reinforcement, using braiding as a manufacturing
technique
Explore the potential of braided BFRP reinforcement in
infrastructure applications

4. Background and Motivation
Degradation of reinforced concrete structures
due to corrosion of steel
affects long-term durability & structural safety of RC elements
Deterioration of global infrastructure
Estimated global cost of corrosion
~ $ 2.5 trillion

5. Background and Motivation
Replacement of steel as internal concrete reinforcement
by FRP composites
Main disadvantage of FRP Brittle failure without warning
Advantages of FRP Corrosion resistant & Lightweight
FRP properties strongly dependent on
❖ Type of fibre & matrix
❖ Fibre & void content
❖ Fibre-matrix interface
❖ Orientation of fibres

6. Background and Motivation
Manufacture methods of FRP:
◆ Pultrusion low cost & continuous process
◆ Braiding additional ductility & increased bond with
concrete
Design guidelines for the efficient use of FRPs in
construction:
◆ ACI-440.1R
◆ CSA-S806-02

7. Background and Motivation
Basic principle of braiding:
Interlacing of yarns in a diagonal direction -
Multiaxial Orientation
Braiding Angle:
Affects mechanical properties of braids

8. Experimental Part
Product name Uses Tensile strength (MPa) Elastic modulus (GPa)
BASALTEX® - Basalt assembled roving –
300, 600, 2400 tex 13, 17, 19 μm
Fibre reinforcement 2800 – 4800 87 - 89
M183 semi-dull round - PET Monofilament Impregnation aid 57 – 60 10
Easy Composites - IN2 Epoxy infusion resin/
Slow cure
Resin 65.5 – 73.5 2.95
Manufacturing design & process of BFRP preforms
Materials
❖ Basalt fibres
❖ PET fibres
❖ Epoxy resin
3 different rebar designs:
❖ 5 mm OD
❖ 8 mm OD
❖ 10 mm OD

9. Experimental Part
Manufacturing design & process of BFRP preforms

10. Experimental Part
BFRP 2 - 8 mm
Layer Material Yarns OD Angle
1 300 8 1.6 12
2 300 16 2.7 16
3 600 16 4.0 17
4 PET 32 4.9 12
5 PET 32 5.6 14
6 300 16 6.5 16
7 600 16 7.2 45
8 600 24 7.9 40
BFRP 1 - 5 mm
Layer Material Yarns OD Angle
1 600 8 2.5 14
2 PET 24 3.8 15
3 PET 24 4.0 15
4 600 16 4.9 45
BFRP 3 - 10 mm
Layer Material Yarns OD Angle
1 300 16 2.6 14
2 600 16 4.2 16
3 PET 32 5.0 13
4 PET 32 5.4 14
5 600 16 5.8 34
6 600 16 6.2 36
7 600 24 7.1 30
8 PET 24 8.0 35
9 600 24 8.8 34
10 600 24 9.8 38

11. Experimental Part
Numerical analysis – Mechanical characterisation
Classical Lamination Theory
(CLT) numerical approach
Evaluation of elastic properties
of braided composites

12. Results
Sample no BFRP 1 BFRP 2 BFRP 3
OD (mm) 5 8 10
Fibre Volume
Fraction (%)*
57.76 51.63 54.59
Aver./ CoV Aver./ CoV Aver./ CoV
Maximum
Load (kN)
5.46/ 0.05 17.84/ 0.01 30.60/ 0.02
Ultimate
Tensile
Strength (MPa)
277.84/ 0.05 354.99/ 0.01 389.64/ 0.02
Maximum
Displacement
(mm)
7.49/ 0.03 10.09/ 0.05 21.58/ 0.07
Ultimate Strain
(%)
2.98/ 0.03 2.59/ 0.06 3.73/ 0.09
Elastic
Modulus (GPa)
10.65/ 0.03 14.76/ 0.02 12.39/ 0.04

13. Results

14. Results

15. Conclusions
• Design, development and characterisation of braided BFRP
composites for internal concrete reinforcement.
• Direct relation between braiding parameters & rebar’s
performance.
• Maximum tensile strength comparable to the one of steel.
• Mechanical response mainly dominated by the textile
architecture, affecting localized properties, crack propagation
and load redistribution in the material.

16. Conclusions
• Significant discrepancies between theoretical and
experimental values for tensile properties, mainly due to the
anisotropic nature and out-of-plane properties of braided
composites.
• Focusing on the design flexibility, additional work towards an
improved rebar design is needed.
• In addition, tensile fatigue tests and microstructure analysis
using CT-scanning technique is currently in progress, aiming
to evaluate their long-term durability, assess quality and
consistency of the manufacturing process and correlate that
with their mechanical performance.

17. sofia.antonopoulou@ucdconnect.ie
The TRUSS ITN project (http://trussitn.eu) has
received funding from the European Union’s
Horizon 2020 research and innovation
programme under the Marie Skłodowska-Curie
grant agreement No. 642453
Thanks for your attention