Definition and Theory
A joint is defined as the connection between two members. Many structures fail not because of a deficiency in a member but because the joints connecting them were not strong enough. There are several factors that will determine the strength of joint between two pieces of wood. One factor is the amount of surface contact between the two members of the joint and the glue/adhesive. Normally, the more surface contact, the stronger the joint. Another factor is the strength of the glue. If the same surface area is used and the strength of the glue/adhesive is changed, the strength of the joint will change.

Procedure

• Gather the 4 or 5 types of glues and adhesives available in your classroom.
• Construct the diagram above using only 1/8" by 1/8" strips (the vertical member is 3" long and the beam member is 2.5" long). Using each glue/adhesive, attach the two 1/8" pieces as shown.
• Clamp the vertical member into a vise for each of the test pieces.
• Suspend a string (piece of thread) 1" from the vertical member with a bucket attached to the string.
• Apply load until the joint breaks and record the amount after each failure.
• Organize the results recorded for each glue/adhesive and surface area in chart form.
• Graph the relationship between the amount of surface contact and the load held for each glue/adhesive used.
• Answer the questions in the lab.

Laboratory Worksheet