Regarding the use of dry tape, I have recently done some (very) preliminary work with Hexcel’s HiTape, using the 4 tow head. I was able to layup an eight ply panel will moderately successful results. A couple of points to note:
- I replaced the elastomeric roller with a metal roller that is covered with an FEP roll cover. This was done primarily to eliminate the possibility of ‘cooking’ the urethane roller, as I was uncertain of the temperature I would need to use for this process.
- The rolls of material need to be kept under a small amount of tension at ALL times, otherwise loops of material will fall to the bottom of the spool, and cause tangles. In order to do this, I put the “slack device controls” in manual mode and kept them on low pressure for the entire time I was running the machine. Since there is no backing tape on the dry fiber, you may need to reduce the tension on the spools by changing the setting on the slip clutches (brakes).
- The final temperature that I used for the torch was around 350°C at 90slpm of N2 flow. This was about as much energy as I could get out of the torch without having excessive torch errors.
- The tape is pretty fragile. That said, I found that it processes very nicely until the sheath around the dry fibers breaks. If that happens, it is difficult to recover.
- Starting a panel has some difficulties, because like thermoplastic matrix materials, the dry fiber tapes have no tack, so will not stick to anything on its own. I used double sided tape on each end of the first ply to hold it in position.
- As the thickness of the panel builds up, the substrate becomes rather compliant (squishy). This tends to make the substrate able to move or shift as a new ply is being placed. I haven’t had a chance to do a much with this issue, however…
- I think that some personnel from your team (maybe you?) have been in contact with folks at AMRC in Sheffield, UK. I know that they have done more work in this line. I think the last person from UNSW that I connected with AMRC was Sonya Brown, and that was just last month, so you may want to speak with her as well.