Реферат: Balsawood Structure Design Essay Research Paper 1

structure will undergo a similar bending due to the load from the

loading cap.

Unfortunately, the data obtained from these tests was not conclusive of

much. The test was flawed due to a bolt which stuck out and restricted

the material?s bending behavior in each test. The two sets of data taken

for this test varied greatly (as much as 300%), and therefore this data

is likely to be very error prone.

Figure 3: Three Point Bending Specimen

Table 3: Bending Data

Specimen # Rupture Load (lb) Elastic Modulus (lb/in)

1 26.6 120,000

2 62.5 442,000

Included in the Appendix is a graph of load versus displacement for the

first test, it shows how the experiment was flawed at the end when the

material hit the bolt which was sticking out of the machine, thus

causing stress again. It also shows the slope from which the elastic

modulus of the material was taken.

Ideally, four point bending tests should have been performed, where the

material is subject to pure bending, and not just shear forces. Further

tests need to be performed using this test, on materials ranging from

plywood style layered balsa, (with similar grains, perpendicular grains,

etc.) This would have been a more useful test if stronger pieces of

balsa had been tested.

3. Glue Testing

The final structure will consist of only balsa wood and glue, thus the

choice of glue is a crucial decision. Glue is weakest in shear, but as

before and to simplify the testing process, specimens will be tested in

torsion, normal to the glue surface. In the actual design, the glue

will mostly be under shear, notably when used to ply several layers of