Carbon-Carbon composites

[Mike Everman]

Found some good general info:
http://composite.about.com/library/PR/2000/bladit1.htm
http://www.composites-by-design.com/carbon-carbon.htm
http://www.iitk.ac.in/infocell/iitk/new ... week42.htm

The key word I was trying to remember was "densification".

[Charles]

Talking of Carbon mark,

I've been wondering what these Carbon valves would be like if used in a pulse-jet design, eBay: 310067377227
I'm just going to read the links as I don't know much about Carbon-graphite? things

Thanks for the information,
Charlie

[Mark]

I'm no expert on anything, but the crux of the matter is fatigue of course. Two stroke reeds designed for piston engines last many hundreds of hours whether steel or composite. But pulsejets are a different environment. A carbon reed is only as heat resistant as its epoxide binder. If you put a carbon reed or spring steel reed in the flame of a propane torch for a few seconds the game will be over, both will suffer greatly.
If you sequester the reeds from heat and flame, whether by putting a protective dish ahead of the reeds or channel them off, you sacrifice some degree of performance or response time. And still you aren't going to get away from physical fatigue unless you are really clever.
It's too bad nobody has contrived a good way to make a rotating reed that senses feedback. Imagine a spinning guillotine blade opening and closing a port in some fashion that mimics the characteristics of a reed valve. That would be the ticket.
One other thing, have you considered linen or cotton reeds? ha

"A conventional reed valve comprises an aperture closed by a resilient flexible member composed of steel or of fibreglass. Suction upon the valve by the engine causes the member to deflect, opening the aperture and admitting air to the engine.
Opening and closing of the valve occurs at a rate equal to the rate of revolution of the engine and creates considerable strain on the flexible member. Fragmentation of the member is regularly encountered.
Reed valves having steel flexible members are disadvantageous in that entry into the engine of fragments of the member causes considerable damage.
Fibreglass valve members are more prone to fragmentation than steel members although fibreglass fragments are not so damaging to the engine.
According to the present invention there is provided an internal combustion engine reed valve comprising an aperture closable by a resilient valve member composed of an epoxide resin.
The valve member is preferably in the form of a laminate composed of epoxide resin and a textile material.
Preferred textile materials include natural fibres such as cotton or linen or artificial fibres such as polyethylene terephthalate, for example the fibre sold by ICI under the trade mark Terylene. Laminates comprising paper, asbestos or other
fabric may also be used. Use of cotton is especially preferred.
Epoxide resin valve members have a greater range of resonant frequencies than fibreglass members. It is important that the valve member is arranged to resonate at the frequencies of actuation of the valve, that is within the range of r.p.m at
which the engine is used.
Epoxide resin textile laminates have a lower density and greater resilience than fibreglass. Resistance to impact fatigue is also greater. The force with which the valve member impinges upon the valve seat is therefore less resulting in reduced
fatigue of the member. Epoxide resin also has a superior modulus of elasticity to fibrelgass. The lower density permits use of thicker laminates having a wider range of mechanical properties e.g. resonant frequencies. A particularly preferred laminate
has a Youngs modulus of 8.00 GNm-2, a density of 1360 kgm -3 and a tensile strength of 1.26×107 kgm-2.
Furthermore epoxide resin does not exhibit the tendency to disintegration once damage has occurred that is characteristic of fibreglass valve members.
The reed valve may be spaced from the engine to reduce thermal damage to the epoxide.
A particularly preferred epoxide is TUFNOL 6F/45, manufactured by Tufnol Limited."
http://www.patentstorm.us/patents/46431 ... ption.html

[Mark]

Talking of Carbon mark,
I've been wondering what these Carbon valves would be like if used in a pulse-jet design, eBay: 310067377227
I'm just going to read the links as I don't know much about Carbon-graphite? things
Thanks for the information,
Charlie

Note they are using rubber coated cages in conjunction with these carbon fiber reeds to pad the impact/slap. Sometimes heat is even an issue for the reeds after the engine stops on a pulsejet.

"This is a NEW set of carbon fiber reeds for the 6 petal rubber coated cages that came stock in the Mercury 3.0L motors. This is aerospace prepeg epoxy in .016" and is MUCH better performing than the TDR ( Tony Dukas) and Boyesen version for this cage. Dyno tests show 6-8hp and we have seen noticable improvement in the 4000rpm and up range. This is the identical material from the manufacturer that Mercury uses for the 280hp factory reeds. Easy installation including instructions if you need them."
http://cgi.ebay.com/ebaymotors/Mercury- ... 0270320793