Sinew Mechanical Properties

[blindarcher]

Hi All!  This is a rather nerdy question, so I apologize in advance.  It may not fall under what one might consider "primitive".  Please keep the responses respectable.  My question is does anyone know or have access to information about Modulus of Elasticity and Poisson's Ratio for sinew, particularly deer and elk or similar creature?  Data is lacking, and understandably so.  I cannot image anyone having an interest in such data other than a few oddballs such as myself.

[mmattockx]

Hi All!  This is a rather nerdy question, so I apologize in advance.  It may not fall under what one might consider "primitive".  Please keep the responses respectable.  My question is does anyone know or have access to information about Modulus of Elasticity and Poisson's Ratio for sinew, particularly deer and elk or similar creature?  Data is lacking, and understandably so.  I cannot image anyone having an interest in such data other than a few oddballs such as myself.

A search on 'animal tendon mechanical properties' will turn up more data than you would expect. It seems that there has been a fair amount of academic research done on this topic for whatever reasons. The numbers vary widely and I don't think I have ever seen data for deer or moose that would be most applicable to bowyers. If you do find some data please post it here as I would be interested in it as well.


Mark

[blindarcher]

Thanks Mark!  I did find several academic papers as you pointed out and found one or two of use, but marginal when considering the purpose.  The unfortunate thing is some of the papers I have yet to review because they cost to download.  Gone are the days when people are willing to share knowledge free of charge.  Bummer.  If I find something, I will share.

FYI, for poops and giggles, I have put together a rigid composite model for analysis of sinew backed bows.  That said, I am afraid it may not be applicable if the sinew acts as a hyperelastic material over the strains associated with drawing a bow.  In that case an energy based approach in characterizing the material may be needed, such as a Mooney Rivlin or Yeoh formulation.  Why would anyone go to this level of analysis? Mostly to quench the relentless thirst (which keeps me awake at night) for understanding the effects of sinew layers on a bow under a variety of environmental conditions (temperature and humidity).  The analysis will also look at the effect of moisture content on the underlying wood core.  So, all of this for which "primitive man" (the smart ones who came before us) already had a good understanding through practical experience.  This may be considered another case of "milking the chicken", where at the end of the day all one has to show for their efforts is sore fingers and an angry bird (assuming the bird does not enjoy the experience).

[bradsmith2010]

I love practical experience,,

[blindarcher]

Thanks for all of your inputs.  I have been fortunate enough to find a few more academic papers that will keep me preoccupied and off the streets for awhile.

[BowEd]

A person needs to fine tune the application of sinew to properly test what sinew can do.

[avcase]

I will dig around for what I have regarding sinew properties. It is certainly possible to model the performance and characteristics of a horn-wood-sinew composite bow with decent accuracy.  The sinew and horn are strained quite high compared to wood. About 3% working strain. It breaks at much higher strain levels.  Often, to check my modeling technique, I measure an existing bow as best as I can to create a model, and then compare the model to the real bow.

Testing a model against a real bow doesn’t tell you if the materials were used optimally.  To do this, I often create samples and measure the properties of these materials myself. 

Alan

[BowEd]

Thickness levels of components and width and length dimensions are something to model after from bow to bow for draw weight.Once a person has a few successful template bows it's a lot easier to gauge for future bows.It takes the guessing game out of the process then.

[Jano]

Adam Karpowicz published these data of tensile modulus for sinew : 0,9 - 2,4 GPa in his book. He also mentioned this source, which I read and appreciate :
 
D.G.Hepworth J.P.Smith  - 2002 - The mechanical properties of composites manufactured from tendon fibres and pearl glue (animal glue)

Free citations from it : "Dry bovine lover leg tendon was found to have a mean tensile modulus of 2,41 GPa and mean strength of 180 MPa. The mean failure strain was 25,6%. Tendon/glue composites formed with wet fibres ( 5cm long in 15 cm sample length and 7mm sample width ) at a fibre volume fraction of 50% were found to have a mean tensile modulus of  2,32 GPa and mean strength of 100 MPa. The mean failure strain was 20,6%. Maximum energy absorption - 18 MJ/m3."

Another values I found are : 2,81 GPa - 2,9 GPa - 1,24 Gpa ...

I also did two ( not very exact ) tests of slim "lateral digital extensor" from deer lover leg tendon in pure elongation and one test of sinew/gelatine layer in three point bending test ( using dial gauge ) personally and got similar results in the range of 2,4 to 2,9 Gpa and maybe more for "prestrained" tendon. ( Please see :
https://atarn.fi/t/grooving-core-before-sinewing/120/15         and up. There is also some modeling in VirtualBow. )

Hope it helps.

[blindarcher]

Thanks All!  Ed, your suggestion falls about modeling based on existing bows is a great one and that is exactly what I did.  To my surprise, I got real good correlation and was able to estimate effects of humidity and moisture content by exposure time and location (upper Midwest, dry arid Southwest).  The results seem very reasonable and compare with some of the findings in Ryan Gill's latest book.

Thanks all!

[PatM]

At the end of the day you are either going to shoot your bow  or not.