Well, obviously, the chassis is steel, of various sorts.  Hard drive chassis are aluminum.  For exact material specifications, you should try contacting a chassis manufacturer, possibly one of the thousands of hits on Alibaba: http://www.alibaba.com/trade/search?SearchText=computer+chassis&Country=&CatId=0&IndexArea=product_en&fsb=y&viewAllCategory=

TTFN

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In a more serious note, recommend you look into the average quantities of abs plastic and epoxy materials used.

You might get this info from companies doing computer recyling.

Do not let the UL94 self extinguishing flamability ratings that these components will have, lead you astray that this stuff won't burn. Bromine and chlorine compounds have been added in the past to  plastics to obtain the self extinguishing characteristic. It doesn't take much imagination to regarding the toxity of the fumes from this burning material.

Under the right conditions it will burn with the vigor you would expect any product derived petroleum would.

I was involved in this many years ago, and can't comment further.
  

The original IBM PC's chassis was made of 16 gage steel, or something pretty close to it, and comprised a large part of the total system weight.

When generic chassis were produced in Taiwan, they tended to be 18 gage, or maybe 20 gage, quite a bit lighter because of a smaller envelope and more and larger openings, and had serious burrs on virtually all edges.

When generic chassis arrived from China, they were made of something around 26 gage, maybe a bit thinner, but had fully rolled or hemmed edges that wouldn't draw blood from an assembler, and weighed next to nothing, or as close as one could ever get with steel.

Vendors of conductive paint keep trying to sell it into the PC market, but nobody has figured out a way to reliably terminate the edges.  Quite a few Apple products' shells are mostly plastic, but are lined with a very thin nickel plated steel wrapper, with lots of sharp little fins that effectively close up the seams wrt to radiated emissions.

So, the proportion of steel in a personal computer has declined over the decades.  The proportion of plastic has risen in roughly complementary fashion.  AFAIK, most of it is ABS or something very similar, because of its unique combination of properties.

Laptops and tablets have their own sets of evolutionary pressures, hence evolved a little differently.
 

Mike Halloran
Pembroke Pines, FL, USA

The OP is so wrong in concept so as to be almost unanswerable and I really wonder why it was asked however I will take a wild stab at it without writing a full text book.

Desktop PCs.

Chassis mostly pressed steel
Circuit board, FRP beased on glass fibre, fillers and epxy or polyester resin plus silver, lead, zinc, copper and even gold plus silicon chips.
Disk drives. mostly cast aluminium with some phenolic resin while the moving parts may be steel and any number of materials
Cases are pressed steel, ABS or PC (if transparent).
Fans, any number of materials, but often ABS, PP, nylon, aluminium or steel.
Electric motors, steel, copper, plastics.
Wires, copper and PE or PVC
Monitors
     Screen, glass or PC
     Case, ABS
Keys on keyboard. PBT.
Plugs and sockets, PBT, mylon, PP
Mouse is PC or ABS or PC/ABS

Notebooks, as above but only PC for screens and maybe cast aluminium for chassis and any number of materials for the case. Often PC/ABS or aluminium or even titanium of Carbon Fibre composites for fashion statement. Scratc pads are PC

I am sure I missed items and materials.

 

Regards
Pat
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My system is wireless, so remove all of the copper and such from Pat's list... mine is mostly made from Unobtanium, a rare element, indeed.

Dan - Owner
http://www.Hi-TecDesigns.com