Talk Composites - The Forum for Advanced Composites

learning resource for structural strength analysis

http://www.talkcomposites.com/Topic25891.aspx

By nathane - 4/27/2018 8:13:23 AM

Hi folks,

I'm gradually preparing for a big project of building an expedition camper habitation unit.  Essentially a 4x2x2m laminated panel box.  It will be built using aramid/carbon/PU foam/carbon vacuum laminated epoxy matrix panels.

My question is: Please can you point me towards where can I find information that will enable me to calculate the fabric weight/thickness required to give appropriate load bearing capacity?

Commercially available polyester/glass equivalent panels are always quoted in terms of thickness (typically 3mm glass/60mm foam/2mm glass) and this isn't very helpful for me because I can't translate it into fabric weight for aramid and carbon (the foam which will remain 60mm for thermal insulation purposes).

I need to be able to specify layup spec for:
  1. Load carrying "beams" longitudinal will be essentially C section (like half RSJ), transverse will be I section (like RSJ).
  2. Panel skins for load distribution to the "beams"
If anyone can point me in the right direction to work out how many layers I will need to use of what weight that would be fantastic.  I do realise that manufacturing technique plays a significant role in the end strength and so there is not a single right answer but I'd like to have a directional understanding to get started.  

Many thanks
Nathan
By oekmont - 4/28/2018 9:38:18 AM

I really wasn't mad at all, sorry if it seemed like I was. I just got the intention (from your second post) that you were seeking for an easy answer from me/us. Sadly, most compositians don't really got an proper mechanical education and are more try and error when it comes to structural parts. Which usually also works quite well. So there are only a hand of people here, who might really recommend their favourite books. Me myself, as I said earlier, only read German introduction level literature, and only advanced and quite specialised papers in english.
if you got only a few, heavy loads, and need mounting points, as well as the possibility to get it with a forklift, I would highly recommend to build an aluminium or even steel frame, and just plank it with composite panels. This does not only make things much easier with calculations and construction, but is far more repairable in standard workshops. With a composite monocoque structure, with structual planning, that one forklift driver we all know could end your trip within a second, leaving you stranded possibly far away from any composite source to get things repaired. At least the structural bottom should be made from forklift proof materials in my opinion. And eyelets are really easy to integrate in metal structures, compared to composites structures. On a long journey safety and reliability always beat a few grams weight reduction.