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"A comparative study on different BFRP rebar design methodologies" presented at CERI2018 by Sofia Antonopoulou

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This study compares the physical properties and tensile behaviour of two different basalt fibre reinforced polymer (BFRP) rebar designs. Both types are developed using basalt fibres and epoxy resin as reinforcement and matrix respectively; composites with a constant cross section of 8 mm diameter are manufactured using a vacuum assisted resin infusion technique. The first configuration consists of eight braided layers at various angles, while the second one combines a unidirectional core with four outer braided layers. The latter hybrid design is introduced to improve the elastic modulus of braided BFRP reinforcement used in concrete structures. Tensile performance of all BFRP rebars produced in UCD laboratory is numerically and experimentally evaluated, and results for both approaches are compared. The effective longitudinal in-plane modulus (E_x^FRP) and the fibre volume fractions (φf) of each sample is calculated using the classical laminate theory and then, tensile tests are performed in accordance to the B2_ACI 440.3R-04 standard to experimentally validate the numerical results. Initial findings indicate that the elastic modulus of BFRP rebar can be enhanced by combining braiding with a unidirectional fibre core while a sufficient tensile strength is obtained, but additional research towards an optimal hybrid design is required.

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"A comparative study on different BFRP rebar design methodologies" presented at CERI2018 by Sofia Antonopoulou

  1. 1. Workshop CERI, UCD, Dublin Wednesday 29th August 2018
  2. 2. Sofia Antonopoulou, Ciaran McNally and Greg Byrne A comparative study on different BFRP rebar design methodologies
  3. 3. Outline ➢Background and Motivation ➢General Research Idea ➢Experimental part ➢Results ➢Conclusions
  4. 4. Background and Motivation Deterioration of global infrastructure Degradation of reinforced concrete structures due to corrosion of steel affects long-term durability, total service life, structural safety of RC elements Estimated global cost of corrosion ~ $ 2.5 trillion
  5. 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. 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. 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. 8. General Research Idea Aim of the project: Main goal: Design, Development & Characterisation of Basalt Fibre Reinforced Polymer composites, for internal concrete reinforcement, using braiding technique & unidirectional fibre approach Explore the potential of braided & hybrid BFRP reinforcement in infrastructure applications
  9. 9. 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 2 different rebar designs: ❖ Fully braided ❖ Hybrid
  10. 10. Experimental Part BFRP 1 - 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 2 - 8 mm Layer Material Yarns OD Angle Core 2400 10 4.4 0 1 PET 24 5.3 30 2 600 8 5.8 45 3 600 8 6.5 45 4 600 12 7.2 45 5 600 12 7.8 45
  11. 11. Experimental Part Numerical analysis – Mechanical characterisation Classical Lamination Theory (CLT) numerical approach Evaluation of elastic properties of braided composites
  12. 12. Results Sample no BFRP 1 BFRP 2 OD (mm) 8 Fibre Volume Fraction (%)* 51.63 48.96 Aver./ CoV Maximum Load (kN) 17.84/ 0.01 17.38/ 0.03 Ultimate Tensile Strength (MPa) 354.99/ 0.01 345.73/ 0.03 Maximum Displacement (mm) 10.09/ 0.05 10.50/ 0.06 Ultimate Strain (%) 2.59/ 0.06 2.50/ 0.10 Elastic Modulus (GPa) 14.76/ 0.02 14.27/ 0.06
  13. 13. Results
  14. 14. Conclusions • This paper focuses on development and characterisation of BFRP composites for internal concrete reinforcement, using both braiding and hybrid designs. • By combining aspects of pultrusion and braiding into a single manufacturing process, a high initial tensile strength is obtained, contributed mostly by the high modulus UD core followed by a gradual failure process associated with the outer braided sleeve. • The maximum tensile strength is comparable to the one of steel and both design approaches exhibited similar mechanical behaviour, although hybrid types can reach higher values with improved fibre volume fractions.
  15. 15. Conclusions • There are also significant discrepancies between theoretical and experimental values for tensile properties on the fully braided type, mainly due to the anisotropic nature & out-of-plane properties of braided composites. The CLT method was instead able to predict the elastic modulus of the hybrid type to a satisfactory degree. • This research contributes to a further understanding on the various available design approaches for FRP composite rebars, although additional work towards an optimal design is needed, focusing on both the design flexibility and the wide availability of manufacturing processes.
  16. 16. sofia.antonopoulou@ucd.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

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