Tension-tension fatigue behavior of hybrid glass/carbon and carbon/carbon composites

This work investigates the quasi-static, low-cycle and fatigue behavior of hybrid glass/ultra-high modulus carbon (GC) and low modulus/ /high modulus carbon (CC) fiber composites. These pseudo-ductile unidirectional interlayer hybrids are a new type of composites whose potential is not yet fully understood, particularly under cyclic/fatigue loading. Different test methods (digital image correlation, video extensometer and thermal camera) were used to record the evolution of the strain, damage and temperature during loading. The results of quasi-static loading shown pseudo-ductile responses with multiple fractures for all the series. The CC specimens exhibited higher initial elastic modulus, ‘yield’ stress and strength, while the GC specimens showed the highest pseudo-ductile strain. Much higher capacity of CC to resist to fatigue loading was observed. In the GC specimens significant damage was accumulated during fatigue loading, when the damage evolution of multiple fractures in different layers developed to delamination between the glass and carbon layers.The authors acknowledge the assistance provided by the technical team of the structural engineering Experimental platform (GIS-ENAC at the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland) for the use of testing equipment, and the support of S&P Clever Reinforcement, that provided the raw materials (E-glass, standard and high modulus carbon sheets and the epoxy adhesive). The first author acknowledge the STSM grant provided by COST Action CA18120 (CERTBOND), supported by COST (European Cooperation in Science and Technology). The second author acknowledge his sabbatical grant SFRH/BSAB/150266/2019, provided by Fundação para a Ciência e a Tecnologia, IP (FCT), financed by European Social Fund and by national funds through the FCT/MCTES and also the financial support by the EPFL/Section of Civil engineering. This work is also part of the research project ‘EasyFloor – Development of composite sandwich panels for rehabilitation of floor buildings’, involving the company ALTO – Perfis Pultrudidos, Lda., CERis/Instituto Superior Técnico and ISISE/University of Minho, supported by FEDER funds through the Operational Program for Operational Program for Competitiveness and Internationalization (POCI) and the Portuguese National Innovation Agency (ANI) – Project No. 3480 (POCI-01-0247-FEDER 003480)