Archived posting to the Leica Users Group, 2009/10/20

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Subject: [Leica] Fender Bender
From: Frank.Dernie at btinternet.com (Frank Dernie)
Date: Tue, 20 Oct 2009 10:18:25 +0100
References: <C702B776.56C91%mark@rabinergroup.com>

Hi Mark,
there are a large number of "plastics".
There are thermosets (which polymerise with heat then don't melt, like  
phenolics (bakelite) and epoxy.
There are thermoplastics which melt and re-set as they cool so they  
can be moulded.
All plastics are very expensive (by weight compared to most metals) so  
cheap fillers are often used to bulk out the items, such as wood  
powder in bakelite. When used for reinforcing strong and/or stiff - 
fibres- are added to the plastic material (not powder). AFAIK carbon  
powder is not used for anything other than protecting rubber from  
sunlight in tyres and so-forth.
Carbon reinforced composites fill a huge range of engineering quality/ 
cost.
At the low end carbon reinforced thermoplastics which can be injection  
moulded are available. They use very short fibres, just a couple of mm  
long, and in fairly small quantities, but the mechanical properties  
are much enhanced. These are the most common to come across.
At the high end long fibres reinforcing thermosets, commonly epoxy, in  
high percentage, in the finished component the carbon fibre will be  
 >60%. The materials are -much- more expensive and only simple shapes  
such as panels and tubes can be made at mass market acceptable prices.  
Complex shapes can have outstanding mechanical qualities but the  
manufacturing methods are very labour, skill, and time  intensive (I  
studied a car made this way for a client 7 or 8 years ago and the  
piece part cost was about 50x more than a BMW 5 series FWIW).
A composite Leica would be stiff, strong, light, have no accuracy  
shifts with temperature and at least 5x more expensive :-)
Fishing rods are pretty high tech., maybe golf club shafts too, but I  
am still too young for golf...
The rest of the commonly seen carbon reinforced products are  
relatively low tech, but very good nevertheless. As I have said before  
I would prefer a carbon reinforced plastic camera shell to a magnesium  
one in terms of fitness-for-purpose, but image and marketing put paid  
to that.
cheers,
Frank

On 20 Oct, 2009, at 05:40, Mark Rabiner wrote:

>> Jim and Rei,
>>
>> Carbon composite has about zero ductility.  Carbon -epoxy composite  
>> is
>> what the Boeing 787  is made of.
>> I work with that stuff every day.  It doesn't bend-- IT BREAKS.
>>
>> Jerry
>
>
> It also what golf clubs and tripods are made of.
> They used to call it plastic.
> Now its called plastic with charcoal dust in it.
> I'm fond of the stuff.
> That and titanium.
> I'm fond of putting all kinds of weird stuff into my A Plus B epoxy  
> mix-up.
> 423
> Graphite
> Powder
> 420
> Aluminum
> Powder
>
> 403
> Microfiber
> Bonding- Thicken resin/hardener mixtures for structural gap filling.
> Bonding with Fillets- Increase joint bonding area and create a  
> structural
> brace.
>
> 406
> Colloidal
> Silica
>
> I learned about this stuff by making my darkroom sink the second time.
>
> Its  the opposite of making a wood boat.
> You keep the water in not out.
>
> http://www.westmarine.com/webapp/wcs/stores/servlet/DisplayPageDynamicView?s
> toreId=10001&langId=-1&catalogId=10001&page=Content&content=west- 
> system-advi
> sor.htm
>
>
> http://www.westmarine.com/
> WEST SYSTEM
>
>
>
>
> Mark William Rabiner
>
>
>
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information



In reply to: Message from mark at rabinergroup.com (Mark Rabiner) ([Leica] Fender Bender)