Influence of Air Plasma Pretreatments on Mechanical Properties in Metal-Reinforced Laminated Wood

Sebastian Dahle,Wolfgang Viöl,Marko Petrič,Georg Avramidis,Kavyashree Srinivasa,Jure Žigon,Arnaud Maxime Cheumani Yona

doi:10.3389/fmats.2021.796474

Abstract

The use of wood-based materials in building and construction is constantly increasing as environmental aspects and sustainability gain importance. For structural applications, however, there are many examples where hybrid material systems are needed to fulfil the specific mechanical requirements of the individual application. In particular, metal reinforcements are a common solution to enhance the mechanical properties of a wooden structural element. Metal-reinforced wood components further help to reduce cross-sectional sizes of load-bearing structures, improve the attachment of masonry or other materials, enhance the seismic safety and tremor dissipation capacity, as well as the durability of the structural elements in highly humid environments and under high permanent mechanical load. A critical factor to achieve these benefits, however, is the mechanical joint between the different material classes, namely the wood and metal parts. Currently, this joint is formed using epoxy or polyurethane (PU) adhesives, the former yielding highest mechanical strengths, whereas the latter presents a compromise between mechanical and economical constraints. Regarding sustainability and economic viability, the utilization of different adhesive systems would be preferable, whereas mechanical stabilities yielded for metal-wood joints do not permit for the use of other common adhesive systems in such structural applications. This study extends previous research on the use of non-thermal air plasma pretreatments for the formation of wood-metal joints. The plasma treatments of Norway spruce [Picea abies (L.) Karst.] wood and anodized (E6/EV1) aluminum AlMgSi0.5 (6060) F22 were optimized, using water contact angle measurements to determine the effect and homogeneity of plasma treatments. The adhesive bond strengths of plasma-pretreated and untreated specimens were tested with commercial 2-component epoxy, PU, melamine-urea formaldehyde (MUF), polyvinyl acetate (PVAc), and construction adhesive glue systems. The influence of plasma treatments on the mechanical performance of the compounds was evaluated for one selected glue system via bending strength tests. The impact of the hybrid interface between metal and wood was isolated for the tests by using five-layer laminates from three wood lamellae enclosing two aluminum plates, thereby excluding the influence of congeneric wood-wood bonds. The effect of the plasma treatments is discussed based on the chemical and physical modifications of the substrates and the respective interaction mechanisms with the glue systems.

Highlights

Wood is one of the most important and most widely used renewable materials in construction, building and furniture applications
In a previous study (Žigon et al, 2020), we investigated the use of air PT for joining beech wood with aluminum and steel using epoxy, PU, melamine urea-formaldehyde (MUF) and polyvinyl acetate (PVAc) adhesives
The results are displayed in three sets, namely the wood specimens as observed parallel to the grain ( ), the wood specimens observed perpendicular to the grain (+) and the aluminum specimens

Summary

Introduction

Wood is one of the most important and most widely used renewable materials in construction, building and furniture applications. Many applications utilize solid wood components, glue-laminated semi-finished products (including plywood, laminated veneer lumber and glulam components) or wood-polymer composites (such as fiberboards, particleboards or oriented strain boards) (Tang et al, 2005; Zhang et al, 2019). A possible way to achieve these requirements is by combining metal and wood into hybrid materials, e.g., by reinforcement of wooden components with metal bars, nets or plates (Soriano et al, 2016; Uzel et al, 2018), and other materials such as fibre-reinforced polymers were tested as reinforcements for wood components (De Vecchi et al, 2008). Many parameters impact the joint’s mechanical performance, including the compatibility of both materials with the adhesive system, surface roughness, geometry of the joint and bond line thickness (Chans et al, 2013; Budhe et al, 2015; Azinović et al, 2018; Peng and Zhang 2018). It is crucial to select an appropriate surface modification technique to yield a well-performing joint (Williams et al, 2014; Da Ponte et al, 2015)

Methods

Results

Conclusion