Abstract

This paper presents experimental, theoretical and numerical studies of wood-CFRP beams bonded with polyurethane (PUR) adhesive. The analyses include two types of CFRP (carbon fibre-reinforced polymer) strengthening configurations and pure glue laminated timber beams as a reference. Through detailed analyses of a double-lap connection on blocks with and without CFRP strips, the authors state that neglecting the cohesive stiffness of adhesive layers may lead to an overestimation of an overall beam’s stiffness. This is significant with wood–CFRP connections, which showed values two times lower than with wood–wood connections. Theoretical modelling of the equivalent area used in a theory of composites provided much stiffer behaviour of the beams than in laboratory experiments. It proves that a PUR glue eliminates the possibility of using simple models that assume a perfect connection between bonded parts. These conclusions led the authors to use the finite element method (FEM) to take into account the cohesive stiffness. The FEM, based on the properties obtained from a double-lap joint analysis, allowed for the precise prediction of the elastic stiffness of the beams.

Highlights

  • Due to the lack of tests bonding wood–CFRP composites on PUR adhesives, we considered this type of bonding for this paper

  • Developing this research may enable the production of wood–CFRP composites in a factory dedicated to glue laminated timber

  • The authors state that taking the cohesive stiffness of the adhesive into consideration is crucial in the case of strengthening wood with CFRP materials

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Summary

Introduction

Using CFRP (carbon fibre-reinforced polymer) is increasingly popular nowadays. Its popularity is growing because it is light-weight and has high stiffness and strength properties. It is used in civil engineering for strengthening existing structures or elements produced in a factory. Researchers have tried to describe the advantages of its composites by various experimental tests. The first is testing gluing wood–wood and wood–FRP connection, and the second one is testing girders of a full cross-section strengthened or reinforced with FRP (fibre-reinforced polymer) tapes

Adhesively Bonded Connections
Strengthening Solid Wood with FRP Strips
Methods
Strengthening GLT with FRP Strips
Introduction Summary
Preparation of the Composite Samples
Gluing process at ABIES
Evaluation of the Cohesive Stiffness of a PUR Adhesive
12. Laboratory tests results for the “K” and “KW”
13. Stiffness measurementthe results for thestiffness samples “K”
15. Finite
Laboratory Tests—Bending
Laboratory
Table 3
Comparison between
Calculations for the
28. Comparison
Conclusions

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