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  1. RPstress

    Use of Al for recent rocket structures vs use of carbon for older ones?

    On TV I've recently seen aluminum isogrid for the SLS fuel tank (Horizon 2014). In the mid-eighties I worked on the Ariane V H10 interstage (the H10 interstage was canceled after the Challenger disaster in 1986 caused cancelation of the Hermes spaceplane (this is according to my memory and may...
  2. RPstress

    "Heat compaction of glass fibers"?

    I few years ago I made the following note in a file I made on glass properties: 'Note that there is a "heat treatment" called "heat compaction" which can increase the moduli by 18% (E-glass) and 9% (S-glass).' I didn't note where I read this and can't remember (sloppy; slap wrist), but I do...
  3. RPstress

    New in the Mojave.

    Seen the latest goings on in the Mojave? A half million pound payload, six engines, 385 ft wingspan. All carbon, of course. Not unambitious, these Californians. http://www.spaceflightinsider.com/organizations/sierra-nevada/new-partnership-sierra-nevada-stratolaunch-join-forces/...
  4. RPstress

    Term for the basic multi-directional stitched-together layers of NCF?

    These days non-crimp fabric seems to come in biaxial (+-45 or 0/90), triaxial (A&P does 0/+-60) or quadriaxial forms. What is the best term for this building block of material(s) that are stitched together? Googling doesn't yield any definitive suggestions that I've found; is there someone out...
  5. RPstress

    Looking for AFWAL-TR-87-3030 damage tolerance paper.

    Horton, R., Whitehead, R., et al, “Damage Tolerance of Composites - Final Report,” AFWAL-TR-87-3030, 1988. It seems quite well hidden (unless my Googling is incompetent). Can anyone help?
  6. RPstress

    Glass weave style numbers, 120, 7781, etc.

    Is there a reasonably authoritative source? There's a few snippets (e.g., Thayercraft.com have a bit of background although the descriptions are sometimes a bit odd) but surely these codes are agreed by cloth manufacurers (sometimes called converters)? Is there an AMS or ASTM standard for such...
  7. RPstress

    Buckling of part of laminate.

    We recently had a failure of a test specimen which we couldn't explain, except for a mechanism like that sketched in the engineering.com picture. (Hopefully that works; it's listed as an 'attachment' in the preview.) Has anyone got any opinions about the viability of the idea? A quick check on...
  8. RPstress

    HS vs IM fibres in CAI tests?

    We are having a bit of trouble with conflicting test results for CAI (basically 30 J impact on the usual ~4 mm thick QI made from UD fibre specimen). There's not much difference for IM fibres compared with the usual HS and we think there should be... Does anyone have experience which they could...
  9. RPstress

    Online basics for composite analysis.

    A while back I asked for an online reference since the references to http://www.mse.mtu.edu/~drjohn/ and http://home.comcast.net/~brandihampson/cd/ have been disappeared. In thread31-343989 TVP references http://www.matter.org.uk/matscicdrom/manual/co.html (a part of the rather neat...
  10. RPstress

    Silicon as reinforcement?

    Just eyeballing the basic properties, silicon looks like a candidate for a high preformance reinforcement. (Strength maybe 7000 MPa, E about 150 GPa, density 2330 kg/m3.) However, I can't find any reference to its use as such (and no references to any sort of fibres of silicon). Anyone aware of...
  11. RPstress

    Reasonably cheap 220¦C resin system needed.

    We have an automotive part with high volume fraction (about 68%) of UD IM carbon and a service temperature of 220°C (430°F). It is currently all 0° fibres in a ring about 300 mm across. Being automotive it's quite sensitive to cost and needs a fairly low cycle time. So, a lot of the usual...
  12. RPstress

    increase in carbon/epoxy modulus with hot/wet?

    We have some data for twill weave HS carbon in epoxy which shows an increase in compression compression modulus for hot/wet tests. Over RT/dry in the 2-direction this is about 15% for 90°C/wet (13% for 70°C/wet). In the 1-direction it is an increase of 9.5% at 90°C/wet (9% for 70°C/wet). There...
  13. RPstress

    Cause of complexity of Cassini's orbit round Saturn?

    See the orbital sample tour at http://en.wikipedia.org/wiki/Cassini%E2%80%93Huygens#Trajectory . I assume there was a significant burn by Cassini for orbital insertion (and maybe a small one when Huygens departed), but what has given the complexity it its orbital path since? Is it...
  14. RPstress

    High-strength bushing material for PH stainless steel?

    Does anybody have any opinions on a high-strength bushing material for PH stainless steel pins (e.g., Custom 465)? We used to use Cu-2%Be at 180 ksi UTS, but the dislike of Be has meant we cannot now do so. Other Cu alloys tend to be rather low strength giving us bearing yield problems. I've...
  15. RPstress

    Peel tests for carbon/epoxy.

    Does anyone have thoughts on what peel tests can be used for testing adhesive between two monolithic carbon/epoxy laminates? The usual sort of monolithic substrate peel that our lab does is typically T-peel and they don't have any suggestions for an 'equivalent' for non-yielding low strain to...
  16. RPstress

    Hybrid laminates.

    Does anyone have experience of hybrid laminates (e.g., carbon and glass or carbon and Kevlar)? We're doing very preliminary design for a bird strike resistant aircraft structure, and would like to get a feel for a starting point. Although the bird will dominate the design, we're interested in...
  17. RPstress

    Shrinkage of flat RTM plaques...

    We have some flat HS carbon fibre/PR 520 epoxy RTM plaques which are coming out a bit thinner than we think they should. The tool cavity is 3.09 mm (0.122") deep at room temp and the cure is 180°C. The final room temp plaque thickness is averaging about 3.026 mm (0.119"), so it's shrinking...
  18. RPstress

    Prepreg tack standard test?

    Traditionally where I am, tack is assessed subjectively, e.g. bend the material through 180 degrees and see how "well" it sticks to itself (basically if stays stuck on or quickly peels off). Does anyone use (or know of) a more numerate test?
  19. RPstress

    UK low alloy steel stress relief - effect on props?

    We have a supplier who wants to stress relieve a machined component made of UK low alloy steel 817M40 (see BS 970-3). They want to do so at 570 deg C (1060 deg F) for 5 hours. (This is to keep dimensional control tight, as they feel it will move a bit when they machine it.) The material's...
  20. RPstress

    Specific heat (Cp) for liquid epoxy?

    Does anyone have a data source for the specific heat (aka Cp, units J/kelvin/cc, etc.; any units welcome) of epoxy while it's liquid? The ever unreliable Internet has given me values from 1.1 to 1.9 J/K/cc for the solid stuff, and I found this paper at lib.physcon.ru/download/p1261.pdf However...

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