EFFECT OF GLUELINE VOIDS ON THE TENSILE-STRENGTH OF FINGER-JOINTED WOOD

Continuing research at Colorado State University is attempting to impr ove the fundamental understanding of the behavior of finger-jointed lu mber loaded in uniaxial tension stresses. As part of this effort. a fi nite element computer program containing a unique boundary element to model the thin glueline was developed and verified. As part of the ver ification process, many finger-joints in dimension lumber were evaluat ed. In the study reported here, 1 00 experimentally evaluated finger-j oints were deliberately mismanufactured and then tested to failure in uniaxial tension. These joints contained a variety of manufacturing de fects including: unglued fingers, unglued fingertips, shaved fingers, starved joints, truncated fingertips, water-soaked fingers, damaged fi ngers, and sawdust contamination of the adhesive. The results showed t hat joint strength varied considerably as a function of the defect pla ced in the joint. Basically, joints that experienced voids along the g lueline and joints with shortened or missing fingers showed a greater reduction in strength than those at had glue throughout the connection . Other processing variables, such as moisture, glue contaminants, and finger thickness and damage had a less significant effect on strength .