Deformation on a sandwich of G10 and honeycomb system
summarized by T.Takeshita 14/April/97
(0) What and how we have measured.
The cross section of the measuring system and the G10+honeycomb sandwich system .
The bottom view of the TGC. The support frames are shown.
(1) How flat is the plane ?
At the first time, we have measured the flatness of the G10 and honeycomb sandwich system. It is found to be perfectly flat within 0.1mm shown in a following figure.
Then we pressed everywhere by the vacuum system. The pressure is measured at a exit to the vacuum pump by a gauge in a unit of mmHg. With the TGC model looked at page 1, there is a frame at Y=0 and at Y=280,560,840 and 1120mm there are wire-support bars marked by the arrows. Almost no deformation is seen at those supported positions clearly. And at the very middle of the support bars, the largest deformations are detected depending on the pressures.
The sized of the deformations are between 0.8mm at 90mmHg, and 0.4mm at 40mmHg at maximum. At the support bar, the deformations are almost zero. This means the G10 and the honeycomb system is strong at the supported points and at other places flexible enough to be ELASTIC which is sketched in a picture below.
To reduce the deformations seen above at (2), we employed 45 pieces of round shaped supports, which are shown in a picture below ;
The results of the deformation measurements are shown in a following figure;
Less than 0.6mm of deformation at maximum is found at the center of supports. The pressures were 40mmHg for all cases to be as small as we can.
BUT we see a little bit of inelasticity around (X=28cm and 34cm) and Y=700mm as a level of 0.2mm. The deformations are seen even at the support bar positions.
(4) Another support system.
After this test(3), we have removed the small pieces. The support bars are set to have 17cm apart for each. There are 8 bars on the TGC surface instead of 5 bars at the test (3). We found the deformation map as a following figure;
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Then we found a global deformation structure at very low pressure, 10mmHg.
At X=40cm, we see a bump on the G10 surface, although we have almost no such structure at X=60cm. The measured heights are not corrected data. This pressure is just for keeping the G10 sheet smooth and flat.
The deformation is measured after 2.5days later similarly. The results are the same. It shows the deformations remains shown above.
This happening could be explained by a following picture; once a local inelastic deformation produced in the honeycomb pulls down the G10 which covers the honeycomb and never comes back to the complete flat surface where it was.
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(5) supplement 1
During the deformation test, we have tested the theory which says the deformation is proportional to the L3, where L is the distance between two supports.
To test the formula, we prepared a following supports; the top view is shown in a picture.
The results are shown in a figure follows;
Since the height of the wire supports is 1.4mm, we see in the Y region from 200 to 550mm the maximum deformation where the plate is touching to the table.
So we just take the data between Y=600 and 1000, we have a figure;
We can see a linear line on the figure which
shows 
.
We have compared two honeycombs. One is sprayed by epoxy glue to become harder. The other one is a normal paper honeycomb. The test is shown in a picture below;
The results are shown in a figure;
By exchanging G10 and honeycomb combinations, we have similar results with the G10