Theatre Design & Technology - Spring 2019 - Public - 31

Wood Platform Measuring 3/4" Deflection at 500 pounds.

PLATFORM FRAME DEFLECTION IN INCHES - 8FT SIDE
1

13/16

DEFLECTION INCHES

test. Once the supports are added, all
three materials are in compliance.
Once the platform comparison with
the stud walls was completed, the apple
boxes were measured. The first attempt
was to put the boxes on the four corners
and place the weight in the same application as had been done with the stud
walls. The results were the same. Adding
boxes to the center of the eight-foot and
zero-foot sides/splitting the center also
gave the same results in deflection rates,
which was minimal across all three of
the platforms. The modulus of elasticity, shear, and moment of inertia analysis
calculations on the carbon fiber tubing
were consistent with the measurements
of deflection that were field measured.
Yale University School of Drama
provided access to a compression testing machine to determine how the carbon fiber tubing would hold up under
stress when compared to steel and wood
columns. In short, as expected, due to
the brittleness of the material, it failed at
a much lower load rate. The test results
are as follows:
* An 18-inch (18") column of two-byone-inch 16-gauge steel tube was compressed up to 18,361 pounds. The only
result was that the wood plate between
the steel and the machine compressed
and lodged into the steel tube. No bending or other failures were detected.
* An 18-inch two-by-four-inch piece of
pine was compressed to 18,089.41
pounds and the only failure was that the
machine indented itself into the top of
the beam. There was a large knot in the
middle of the beam that was anticipated to potentially cause some structural
issues, yet no real failure was detected.
* An 18-inch two-by-two-inch braided carbon fiber column was tested
and reached catastrophic failure at
3,309.29 pounds. The tube started to
compress, the fibers frayed, and the column cracked in the middle, opening up
the tube.
* Another piece of two-by-two-inch
braided carbon fiber was tested on the
horizontal side. Catastrophic failure occurred at 670.15 pounds and the tubing collapsed into itself and bounced
back with cracks on the long side of the
braids.
All in all, the carbon fiber seemed to be
more brittle than the steel or wood, yet
performed mostly as anticipated.

3/4

3/4
5/8
17/32

1/2

13/32

1/2

13/32
5/16

1/4

1/4
3/32

3/32

1/4

7/32

1/8

1/32 1/32

0 LBS

100 LBS

200 LBS

WOOD

Other Considerations
Despite the benefits of the material
overall, the cost of carbon fiber varies
widely depending on the application and
strength, like any other material. There
are only 12 carbon fiber manufacturers
in the United States, and a good deal of
carbon fiber is manufactured in other
countries. Because of this low number,
manufacturing still has not reached
market saturation levels. That reality,
along with growing demand for carbon
fiber composites, which are projected to

300 LBS

STEEL

400 LBS

500 LBS

CARBON FIBER

increase approximately 10 percent per
year through 2024, should help drive
prices lower (Cook and Booth 2017, 6).
Carbon fiber costs approximately
5,723 percent the cost of pine wood
and 2,580 percent the cost of 16-gauge
steel. However, with 2018/2019 U.S.
economic and trade policies with foreign
importers of materials such as China,
Mexico, Japan, and Europe imposing
tariffs on wood, steel, and aluminum, as
well as imports from other countries, we
have seen an obvious increase in pricSPRING 2019

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