[RocketsNW] Silk Lay-Ups

Mon Feb 1 12:54:45 PST 2010

Silk may or may not be a good reinforcement material, but don't think of it
as a replacement for CF or even glass.  Think of it as a replacement for
nylon - it was used for parachutes and women were stuck with nylon hose
during WWII.

I did a quick look and found the attached webpage with some mechanical data
on spider silk http://www.tiem.utk.edu/~mbeals/spider.html.  I know this is
not the moth silk used to make silk fabric, but the properties are probably
in the same ballpark.  As you can see the modulus reaches a peak of about
280 MPa, but the strain at failure is nearly 500%!

Depending upon the source material and the heat treatment carbon fiber can
have a modulus form about 100 to 500 GPa - about a 1000 times higher than
the spider silk.  It is also stronger with a tensile strength from about 2
to 5.5 GPa while the spider silk was around 1.3 GPa.  However, the strain at
failure for CF is generally very low - less than 10% is common.

Kevlar has a modulus of 80 - 186 GPa, a breaking strength of 3.4 - 4.1 GPa,
and strain at failure of 2 - 4% depending upon the grade.

The glass fiber used in cloth has a modulus of 80 - 90 GPa and a strength of
2 (e-glass) to 4 (s-glass) GPa.  Strain at failure will be very small as
well.

Nylon-66 has a modulus of 1.7 - 3.4 GPa, strength of 40 - 80 MPa, and
elongation at failure of up to 300% depending upon treatment.

In summary I would think that the silk would be very good where you want to
reinforce with some flexibility (i.e. the longbow example).  I can also see
it on some smaller rockets with a somewhat flexible matrix to give some
reinforcement that gives - i.e. a 29 - 38 mm machbuster or boosted dart.
Finally, a nice patterned silk would look really cool with the correct clear
matrix.  I wonder if you could spray on a good automotive clear coat and lay
it on smoothly before it sets?

Marty

-----Original Message-----
From: rockets-bounces at rocketsnw.com [mailto:rockets-bounces at rocketsnw.com]
On Behalf Of Sam Grado
Sent: Monday, February 01, 2010 11:54 AM
To: CAMERON Kenneth A; greg at blastzone.com
Cc: rockets at rocketsnw.com
Subject: Re: [RocketsNW] Silk Lay-Ups

Silk is less expensive than CF. About the same to a little less in cost than
some grades of seaglass cloth. It may possess better flexural strength than
'glass cloth with less overall weight. Just something to explore in view of
the cost of CF. Could be a good augment to CF.

Sam Grado
TRA L2

"If you're going to build it, build it from scratch"!

sales at pvconly.com
http://www.pvconly.com
http://www.sugarshot.org/bios/sgrado.html
http://groups.google.com/group/PVC-Motor-Rockets

--- On Mon, 2/1/10, greg at blastzone.com <greg at blastzone.com> wrote:

From: greg at blastzone.com <greg at blastzone.com>
Subject: Re: [RocketsNW] Silk Lay-Ups
To: "CAMERON Kenneth A" <CAMERON.Kenneth at deq.state.or.us>
Cc: rockets at rocketsnw.com
Date: Monday, February 1, 2010, 1:39 PM

So whats the upside here?  Is silk less expensive than fiberglass or other
composites?  Better in some way?  Or is this just a desire to try something
different for fun?

On Mon, 1 Feb 2010 11:16:45 -0800, "CAMERON Kenneth A"
<CAMERON.Kenneth at deq.state.or.us> wrote:
> Greetings
> While not directly tied to rocketry, I can attest to the fact that silk
> can increase resistance to flexing in some instances.  As a traditional
> archer who teaches folks how to make wooden longbows and flatbows, I've
> used silk as backing on an English longbow and it increased the pull
> weight (i.e. stiffness) from 55 pounds to 75 pounds.  This was with two
> layers of raw silk cloth attached with carpenters glue.  I also know
> that multi-layer varnished silk was used as light armor (though I prefer
> chain mail, I teach classes in that, too).  Imagine the look on the
> clerk's face at the fabric store when you ask if she knows how well silk
> stands up to speeds above mach one.
> Ken Cameron
> Brewer to the Gods of Valhalla (at least that's who the said they were)
> 
> -----Original Message-----
> From: rockets-bounces at rocketsnw.com
> [mailto:rockets-bounces at rocketsnw.com] On Behalf Of Bill Munds
> Sent: Monday, February 01, 2010 10:53 AM
> To: vonrang at yahoo.com; Dave Randall; rockets at rocketsnw.com
> Subject: Re: [RocketsNW] Silk Lay-Ups
> 
> 
> Sam,
> 
> Why not test it?  Newspaper and white glue work pretty well structurally
> (Jr. High science project).
> 
> I would think that silk being pretty strong by itself would work if in
> multiple layers in different directions.
> 
>  
> 
> Hmmm.......
> 
> 
> 
> 
> 
>  
>> Date: Mon, 1 Feb 2010 07:33:48 -0800
>> From: vonrang at yahoo.com
>> To: dmrandall at gmail.com; rockets at rocketsnw.com
>> Subject: Re: [RocketsNW] Silk Lay-Ups
>> 
>> Yes, silk fabric for axial flexture and sheer strength.
>> 
>> 
>> Sam Grado
>> TRA L2
>> 
>> "If you're going to build it, build it from scratch"!
>> 
>> sales at pvconly.com
>> http://www.pvconly.com
>> http://www.sugarshot.org/bios/sgrado.html
>> http://groups.google.com/group/PVC-Motor-Rockets
>> 
>> --- On Mon, 2/1/10, Dave Randall <dmrandall at gmail.com> wrote:
>> 
>> 
>> From: Dave Randall <dmrandall at gmail.com>
>> Subject: Re: [RocketsNW] Silk Lay-Ups
>> To: "Sam Grado" <vonrang at yahoo.com>
>> Date: Monday, February 1, 2010, 8:40 AM
>> 
>> 
>> Sam,
>> 
>> I've embedded different cloths in a couple of rockets for decorative
>> purposes (not strength)... Is that what you're asking about, or is it
>> for strength?
>> 
>> Dave
>> 
>> On Mon, Feb 1, 2010 at 4:56 AM, Sam Grado <vonrang at yahoo.com> wrote:
>> > Has anyone here worked with silk cloth for airframe lay-ups?
>> >
>> > Sam Grado
>> > TRA L2
>> >
>> > "If you're going to build it, build it from scratch"!
>> >
>> > sales at pvconly.com
>> > http://www.pvconly.com
>> > http://www.sugarshot.org/bios/sgrado.html
>> > http://groups.google.com/group/PVC-Motor-Rockets
>> >
>> >
>> >
>> > _______________________________________________
>> > Rockets mailing list
>> > Rockets at rocketsnw.com
>> > http://mx1.blastzone.com/mailman/listinfo/rockets
>> >
>> >
>> 
>> 
>> 
>> -- 
>> - Dave
>> 
>> 
>> 
>> 
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