|Bachelorprojekt, 1. modul, 2011, id:279|
|Findes på RUb:||Ja|
Woodwelding is a novel method used to connect two pieces of wood. One of several wood welding tecniques is linear wood welding where two pieces of wood are held together under high preasure while one of the wood pieces is shiftet linerly back and forth with a high frequency. This creates a bond of several megapasca between the wood pieces. It has been shown that the orientation of the grain has an influence on the streanght of the bond, but no explination has been given for this phenonema. This report is an attempt to shead some light on the matter. Softwood is mainly composed of tracheids which are long cylendrical cells. Inside the cell wall of theese tracheids one finds, amongst other things, microfibrils, which are long cellulose chain. The microfibrills form an angle with respect to the tracheid axis which is called the microfibrill angle. The microfibrill angle has an influence on the mechanical properties of the wood. We weld wood together with different orientation of the gain and measure the elastic modolus of the bond that is formed. The method used to investigate the structure of the bond at nanno scale is small-angle x-ray scattering. The microfibrill angle, the radius of the microfibrils and the elastic modulus was determined. The aim is to investigate the connection between the orientation of the wood grain during welding and the elastic modulus and nano structure of the bond. The elastic modolus changes with different orientation of the gain and our results suggest that there is a connection between the orientation of the grain and the elastic modulus. We find that the microfibril angle changes as one scans across the bond and the closer one gets to the center of the bond the higher the degree of disorder becoms. We found no clear connection between the change in microfibril angle, microfibril radius and the elastic modulus.