• Kanerva, Mikko Samuli
• Orell, Olli Aleksi
• Ramakrishnan, Karthik
• Sarlin, Essi Linnea
• Hokka, Mikko

Abstract

The feasibility of replacing traditional composite reinforcements with natural fibres has been investigated in the past two decades and this increased interest in bio-based alternatives is driven by the urgent need to address climate change and to satisfy carbon emission reduction targets set by legislation around the world. Natural fibres such as from flax plant (Linum usitatissimum) exhibit high specific properties due to their low density and also have a positive environmental profile as they are a renewable resource that requires less energy to manufacture, with the added potential for energy recovery at end of life. Significant research is currently in progress to overcome obstacles such as moisture absorption, inadequate toughness, poor impact resistance and reduced long-term stability in outdoor conditions. One of the solutions proposed for the increased use of natural fibre composites is hybridisation, either with synthetic fibres or with metals. Hybrid structures combine two or more materials to produce lightweight materials with functional properties such as corrosion resistance, vibration damping and impact resistance. The synergistic effect of the hybrid materials produces desirable outcomes such as reductions in energy consumption, and improved cost efficiency. Fibre Metal Laminates (FML), for instance, are hybrid composites that combine the superior fatigue and fracture characteristics of fibre reinforced composites, with the plastic behaviour and durability offered by metallic materials. We propose a stainless steel metal substrate instead of more typical aluminium for the fibre metal laminate. However, the adhesion between stainless steel and polymeric materials, especially thermoplastic composites is generally poor and improved solutions for the manufacturing of biocomposite hybrids are needed. In this study, adhesion between stainless steel and flax fibre reinforced epoxy composite (FFRP) formed by vulcanising a thin rubber layer is investigated. Natural rubber formulated by Teknikum Oy was used for the adhesion of the steel and composite layers. A commercial epoxy adhesive 3M™ Scotch-Weld™ epoxy adhesive paste DP460 was also used to produce the steel/composite hybrid samples as this toughened adhesive exhibits good peel, shear and impact properties. The adhesion properties are characterised using a lap shear test and full-field displacement optical measurement methods. The Digital Image Correlation (DIC) system is used to study the shear failure of the adhesive bond. The microstructure of the interfaces were characterised using microscopy.

Topics

• density
• impedance spectroscopy
• microstructure
• Carbon
• stainless steel
• corrosion
• aluminium
• laser emission spectroscopy
• shear test
• fatigue
• composite
• durability
• thermoplastic
• rubber
• microscopy