NICK TSAMIS AERE 423 FALL 2009 Composite Rockoon Parts

Purpose of Project The ISU Rockoon Team is a project dedicated to launching a Rocket/High-Altitude weather balloon structure to ~85,000 ft. then igniting the payload rocket at this altitude. Nick Tsamis is the composites group leader for the team and used the project to support the team in building any of the composites necessary for the advancement and success of the project. Public info about the project: 

What the Project Entails 1) Pre-preg Carbon Fiber electronics tray for the payload box. 2) Pre-preg Carbon Fiber electronics tray for the rocket’s coupler. 3) Pre-preg Carbon Fiber Rocket Fins to be used later for testing and re-design.

The Current Payload Box

Emphasis of the Project Weight was the main driving factor in all of the pieces made for this project. The pieces were to replace old fiberglass boards. Strength was not a major concern. Stress/strain analysis was not necessary for the project due to the non-existence of strength requirements for the pieces. It was assumed that because these pieces are not high-load bearing composites, their strength alone would be more than satisfactory. A new manufacturing technique is also being tested.

Methodology Used After weight considerations, manufacturing quality was the second most important aspect of the project. Extreme care during bagging procedures was critical The heated press was used to create a nice finish all the way throughout the parts as well as a to make a highly reproducible part. A new methodology for the heated press was used that had never been attempted before. Since the trays were all to be of the same size and 4 of them were needed, all 4 trays were attempted to be laid together in the same press.

Temperature and Pressure Considerations Min Temp. – Room Temperature ~80 F Max Temp. – 350 F due to presses ability Min Press. – 2160 psi Max Press. – 7.2 tons force One cycle with temperature and pressure holds at 250 F and 350 F at 7.2 tons psi. Entire cycle takes about 3 hours

Heated Press Profile Used Room Temperature, vacuum sealed 250 Degrees F Increase pressure to 7.2 tons force 350 Degrees F Full pressure at 7.2 tons force Cooled to Room Temperature Pressure returns to normal Held for 60 minutes Held for 120 minutes Temperature increased linearly from room temp to 250 F Pressure increased linearly from 1.08 tons to 7.2 tons Temperature decreased linearly from 350 F to 80 F Pressure decreased linearly from 7.2 tons to 0 tons

First Layup - Specs To be used for the electronics tray of the rocket. Needed to be ~.125 inches thick Purpose was to be as lightweight as possible A 12 inch by 12 inch pre-preg CF sheet was to be constructed. Total of 15 plies of pre-preg to be used for one sheet Plies were laid alternating at [0 8, 90 7 ] for weight reduction but to maintain durability. After it is made, it is to be cut to 12 inches long by 74mm wide to fit into the rocket’s coupler

First Layup - Picture

Electronics Tray - Cut

Electronics Tray – In Rocket’s Coupler

Second Layup – Specs New manufacturing technique was to be tested 4 Trays for the project’s payload box, (containing the transmitter and any test equipment used for test launches) were to be constructed All trays were to be 12 inches by 12 inches Again, strength not an issue- used as fiberglass tray replacements due to the fiberglass being overly heavy (as well as overly rigid) Total of 6 plies were used for each sheet Again plies were laid alternating at [0 3, 90 3 ]

CF Trays – New Technique Due to the new technique, we didn’t know what to expect considering the release film specifically. Bagging technique was similar to any normal bagging except that an extra layer of exterior bagging film was used in between each CF laminae sample for extra security. Each 6 ply sample was wrapped first with one sheet of release file on each side, then one sheet of exterior bagging film. The entire sample was then put under vacuum and heat-pressed.

Fiberglass Trays to be replaced

Pre-preg CF Replacement Trays

Tray Results The new procedure worked very well. The four sheets were of a very fine quality and all were within 4 grams of each other! Weight considerations:  The fiberglass trays are 8 in. by 8 in. sheets weighing in at average of 130 grams each.  The CF trays were 12 in. by 12 in. sheets weighing in at average of 120 grams each. Overall weight drop of 41% !! The trays are still within strength requirements, (they hold all necessary electronics with ease) and less rigid (easier for our box to handle)

Bending Issue with Tray 4 It is evident in the image that the fourth final product has a severe bend to it. It is my belief that this is not due to the manufacturing procedure, but rather to an occurrence before the laminae were bagged to get pressed. One of the samples had weight placed on it in the lab and the sample was not pressed and refrozen so I believe this is the reason.

Bending Issue with Tray 4 Another possible option is that perhaps one of the plies was not alternated. This seems less likely to me as there were only 6 plies total and the beginning and ending sheets were in different directions This implies that the mis-alternating error would have had to have happened twice in the same sample. Again, still possible, perhaps not plausible.

Overall Results Overall the project was a terrific success! The parts are of a very fine quality and they work! The rocket’s electronics tray has already been put to use and is performing just as we had hoped. The trays will be installed as the last designs for the new payload box is finalized. The 4 th sample that ending up bending will not be wasted. The team has plans to put it to use in testing for thermal conductivity and perhaps tests to help us better our final rocket fin design.