The Characteristics of Glued Tensile Shear Strength Constituted of Wood Cut by CO_(2) Laser

The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method.This paper investigates the influence of CO_(2) laser cutting on the wetting properties,the modified che-mical component of the laser-cut surface,and the strength and adhesive penetration near the bondline.Beech-wood is cut by the laser with varying processing parameters,cutting speeds,gas pressures,and focal point positions.The laser-cut samples were divided into two groups,sanded and non-sanded samples.Polyvinyl acetate adhesive(PVAc)was used to bond the groups of laser-cut samples.After assembly with cold pressing,the tensile shear test was carried out.Numerical modelling was carried out to determine the partial elongation and shear strain of the glue line.Based on this,the shear modulus and linear elasticity of the glue line were estimated.Scan-ning electron microscopy was used to assess the adhesive penetration into the porosity structure of the laser-cut samples,and the depth of the heat-affected zone.The laser-cut surface was analysed by Fourier transform infrared spectroscopy.The wetting properties of the laser-cut surface were investigated by using a contact angle goni-ometer.The numerical model of the strain-stress curve confirmed the experimental model.The highest modulus of the linear elasticity of the glue in the numerical calculation belongs to the joint containing laser-cut samples at a gas pressure of 21(bar).The penetration depth of PVAc adhesive into the porosity structure of the laser-cut sam-ples was similar to that of sawn samples.The deepest heat-affected zone in the laser-cut samples was 150µm.A PVAc drop disappeared immediately on the laser-cut surface without sanding,but gradually on the sanded surface.In contrast,the drop on the sawn surface remained with an angle of 32°–48°.The degradation of hemi-cellulose and lignin was proven by the lower intensity of the C=O and C-O Bonds,compared to the sawn surface.

Effect of Surface Texture on Tensile Shear Strength of 1060Al-PET Welding Joints

Joining metal to plastic can lighten weight of products to reduce energy consumption.However,it is difficult to achieve high-strength welding between metal and plastic.To address this problem,the methods of surface texture pretreatment and laser irradiation welding was proposed to achieve the high-strength connection of metal and plastic.In this study,with different parameters of laser power and texture morphology,1060 Al with surface texture treatment was joined to polyethylene terephthalate(PET)by laser irradiation welding from metal side.Study showed that as the laser power increased,the tensile shear strength of joints increased first,and decreased thereafter.Tensile shear tests demonstrated that the mechanical force of joint was strengthened contributed to mechanical anchorage formed by surface texture.The depth-width ratio of the texture grooves affected the tensile shear process of the joint.According to the result of temperature simulation,the existence of texture grooves reduced the heat transfer efficiency,and the heat dissipation at interface was also impeded in course of laser welding.Finally,the maximum tensile strength of 1060Al-PET joint reached 48.4 MPa,which was close to the strength of PET matrix.The bonding mechanism of the 1060Al-PET joints was composed of mechanical bonding and chemical bonding.This study proposes an effective method to join metal to plastic which achieved high-strength connection between metal and plastic.

Microstructure and mechanical properties of Mg-to-Al dissimilar welded joints with an Ag interlayer using ultrasonic spot welding

Lightweight ZEK100-0 Mg alloy and A16022-T43 Al alloy with an Ag interlayer were joined via ultrasonic spot welding(USW),focusing on the microstructural change and tensile lap shear strength of the welded joints in relation to welding energy.Mg/Al interface was superseded by Mg/Ag and Al/Ag interfaces,and unfavorable Mg门A-intermetallic compound was eliminated.Ag foil was observed to be intact in the nugget center,while it was broken or dissolved at the nugget edge at high welding energy levels.The diffusion layer at the Mg/Ag interface consisted of two distinctive sub-layers:Mg3Ag intermetallic compound adjoining Ag foil,and Mg3Ag-l-Mg eutectic structure adjacent to Mg.Only a thin diffusion layer consisting mainly of Ag3Al occurred al lhe Al/Ag interface.The tensile lap shear strength first increased,reached its peak value,and then decreased with increasing welding energy.The shear strength achieved in the present study was〜31%higher than that of the joint without interlayer.Interfacial failure occurred at all energy levels,with Ag foil particles or fragments being stuck on both Mg and Al sides due to its intense interaction with Mg and Al via accelerated diffusion during USW.The results obtained pave the way for the challenging dissimilar welding between Mg and Al alloys.

A novel seal-flow multi-vortex friction stir lap welding of metal to polymer matrix composites

The friction stir lap welding(FSLW)of metal to polymer is a challenging work due to the unavoidable polymer overflowing.Facing this problem,a novel seal-flow multi-vortex friction stir lap welding(SM-FSLW)technology based on the subversively-designed multi-step pin was put forward.Choosing 7075 aluminum alloy and short glass fiber-reinforced polyether ether ketone(PEEK)as research subjects,the welding temperature,material flow,formation and tensile shear strength of dissimilar materials lap joint under the SM-FSLW were studied and compared with those under traditional FSLW based on the conical pin.The multi-step pin rather than the conical pin effectively hindered the polymer overflowing due to the formation of vortexes by the step,thereby attaining a joint with a smooth surface.Compared with traditional FSLW,the SMFSLW obtained the higher welding temperature,the more violent material flow and the larger area with high flow velocity,thereby producing the macro-mechanical and micro-mechanical interlockings and then heightening the joint loading capacity.The tensile shear strength of lap joint under SM-FSLW was 27.8% higher than that under traditional FSLW.The SM-FSLW technology using the multi-step pin provides an effective way on obtaining a heterogeneous lap joint of metal to polymer with the excellent formation and high strength.