Improving Bonding Strength Between Steel and Wood Based on Laser Surface Texture
Composite components made of wood and steel glued together have the advantages of these two materials,which improve the mechanical properties of single-material components.An increasing number of steel-wood composite parts are used in buildings.However,the surface roughness of untreated steel is low,and pollutants and oxide films are present on the steel surface.These factors are not conducive to the adhesion of adhesives on steel,resulting in a low bonding strength between steel and wood in the steel-wood composite member,weakening the ability of steel and wood to bond together.This paper aims to improve the adhesive adhesion ability of steel to enhance its bonding strength with wood.The use of lasers is proposed to form microtextures on steel surfaces to increase the contact area and embedment depth of the adhesive.A single-lap shear test is conducted to evaluate the effects of the texture shape(square pits,vertical grooves,and transverse grooves)and textured steel with and without sanding treatment on the bonding strength of steel and wood.A laser confocal profilometer is used to detect the roughness of the steel surface before and after the laser treatment,the roughness of the textured steel before and after the sanding treatment,and the texture depth.The surface morphological features of the laser-treated steel,surface characteristics of the textured steel after sandpaper grinding or without sandpaper grinding,and the shear bonding fracture characteristics of the specimens are examined using scanning electron microscopy(SEM).A finite element model is constructed based on the design parameters and test data(texture width,spacing,and depth)to study the influence of the texture shape on the stress distribution of the adhesive layer between the steel and wood and the trend of the bond strength between the steel and timber.The law and mechanism of influence of the steel surface texture on the bonding strength of steel and wood are summarized.The results showed that the microtexture processed on the steel surface by the laser could effectively increase the surface roughness of the steel.The rough surface expands the contact area between the adhesive and steel.This promotes the mechanical interlocking of the adhesive and steel,thereby improving the bond strength between steel and wood.The numerical simulations and experiments showed that the texture shape affects the roughness of the steel surface and the body of the"glue nail"formed by the adhesive penetrating the micropores,which plays a controlling role in the adhesion of the bond to the steel.Under the same laser setting and texture design parameters(width and spacing),the groove texture improved the roughness more than the square texture,which was more conducive to increasing the bond strength between the adhesive and steel.The laser melts existing around the surface can increase the roughness and hinder the bond failure of the glue in the shear direction to a certain extent,which is conducive to improving the bond strength between the adhesive and steel.The research results can provide technical support for enhancing the bonding strength of steel and wood and provide a new idea for the application and design of texture in steel-wood composite components formed by gluing.
laser surface treatmentmicro-texturebonding strengthbonded steel-wood composite member
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