Archived posting to the Leica Users Group, 2009/10/20
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]======================================== Message du 20/10/09 11:19 De : "Frank Dernie" A : "Leica Users Group" Copie ? : Objet : Re: [Leica] Fender Bender Hi Mark, there are a large number of "plastics". There are thermosets (which polymerise with heat then don't melt, like phenolics (bakelite) Bakelite, who said bakelite? Time for Islay - nice of of bakelite inside , and green from start to tasting. Phx 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 _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information