Spacecraft Honeycomb 2

I'd worry about out-gassing, but I'm sure composite structures are used ... I'd suspect with reduced allowables.

another day in paradise, or is paradise one day closer ?

Thanks rb1957!

I don't see any much project example using CFRP with aluminum honeycomb except the following...

I meant that I'm sure there are composite structures in satellites (not necessarily honeycomb panels) ... but composites are composites. If they need special allowables for the space environment then this "should" be reasonably understood (though maybe not for the specific composite you're thinking of).

another day in paradise, or is paradise one day closer ?

Don't know about structural components, but there are electro-optical sensor payloads with composites used for the main telescope housings. This has been getting to be a big deal for demisability, although aluminum is pretty demisable on its own.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list

S...

Honeycomb panels are used extensively for launch vehicle jettisonable fairings and inter-stage parts... but most satellite structure relies on monolithic sheets/panels. BTW the honeycomb panels in these cases are made for noise/vibration control/deadening and are 'naturally vented' to quickly vent-off internal core-cell air pressure during high friction/heating ascent and reducing atmospheric pressure to '0'... using perforated honeycomb core materials... that could be composite/paper and aluminum foils/cell-walls, as design dictates. This could extend to other expendable components that would have limited critical structural performance life and will be jettisoned later in the flight profile.

I think the reasons for using monolith parts [primarily metallic] for the dedicated spacecraft... that are integral [integrally made] and then sections fastened together... is to eliminate any reliance on adhesive bonding in the harsh environment of space, which is known to degrade most non-metallic materials... heat-cold, radiation, atomic gasses/ions, etc... and makes long-term absolute structural integrity for critical composite and bonded assets impossible to be validated as 100% reliable. The ONLY exception to this might be stainless steel or titanium perforated honeycomb core and face-sheet/skin panels that are welded or brazed together... not adhesive-bonded.

NOTES1:
a. Spacecraft are subject to venting of trapped gasses for days/weeks/years from every micro-voids/pore... and honeycomb and composite materials [especially composite/paper honeycomb] are especially vulnerable to this phenomena.
b. The plastic body Tesla that SpaceX launched into inter solar space is predicted to soon-be a mass of fragile junk, as it comes-apart, because of non-metallic materials degradation.
c. The [4] landing gear struts for the Apollo lunar modules used a honeycomb filler material for struct shock attenuation [by crushing/compacting] on lunar landing... but they were never intended for long-duration exposure, before fulfilling their 1-time critical function.
d. If trapped air is subject to deep-cryogenic temperatures, the it will usually liquify... forming LN2, LO2, LAr2, etc. Now, imagine what happens if liquified gases are suddenly exposed to high aero-friction heating... when trapped in core cells or even small voids???!!!!
e. I am pretty sure that even interior panels of the ISS are NOT honeycomb for a multitude of reasons, that are far-beyond this discussion.
f. Hint (e)… one-of many other serious issues. SAE AIR5661 Compartment Decompression Analysis is worth reading... everything blows apart in incredible and scary ways... and structural integrity is really hard to maintain.

NOTE2.
In the 1990s a unique materials experiment was placed into orbit by a Space Shuttle... the [huge] Long Duration Exposure Facility. The LDEF exposed hundreds of materials [including coatings, insulation, plastics, wires, etc] to low earth orbit. LDEF was designed to 'stay-up' just for ~1 year... but due the loss of the SS Challenger... spent many years in LEO before it was retrieved by another Space Shuttle. It was a gold-mine for materials performance in the harsh space LEO environment. The subsequent reports of findings are in several very interesting NASA/CR reports... although some findings may [still] be classified.

Gotta-go-back-to-work...

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

Hi WKTaylor,

Does perforated honeycomb core give different properties compared to same spec but non-perforated honeycomb core?

The Hexcel spec highlight the the honeycomb cell wall has perforated and non-perforated but the mechanical properties are for general honeycomb core... does it mean perforated cell wall no impact on the properties?

it could be that perforated cells don't become little air tanks ? (imagine 1 atmosphere inside a cell and a vacuum outside)

it could also be that it (perforation) helps potting compound to penetrate the core better.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

I think Hexcell is sold as open cell, i.e., no faces; I think the perforation refers to perforating the walls of the honeycomb, which has to be done prior to the forming of the half hexagons that are then bonded together to form full hexagons



TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list

Most core wall perforations probably have little to no effect on core properties. Core shear and compression strength are typically controlled by cell wall buckling.

Most hex core is made by bonding sheets, then expanding the bonded sheet stack into hex shapes.

I struggle to believe Hexcel or Nomex or whatever they call themselves can't identify when you'd use perf or non perf hex.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

Spacecraft use perforated core to vent the gas inside quickly after launch. Most other uses are non- perforated because breathing due to pressure/temperature changes will eventually lead to the cells filling with water.