Composite Materials/weight fraction


QUESTION: sir, I am frabricated specimens of coir and epoxy with hand lay up method ,as per 30:70,40:60,50:50 weight fraction,suppose I have taken 10 gm fiber web,what are the resin weight for above mentioned ratios?

ANSWER: If you search my archived responses in this site you will find the answer because I have responded to this question before.
You need to know or measure the density of coir and epoxy.
The equations are easy.
The are in chapter 4 of my 2011 textbook.

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QUESTION: Dont mind sir,I does not get answer,density of coir fiber is 1.2gm/cm3 and density of epoxy resin is 1.1 gm/cm3.Can you tell me,for coir fiber and epoxy resin what should be range of mixing?

Use Eq. (4.8) in this textbook:
1/rho_c = W_f/rho_f + W_m/rho_m
where (c) composite, (f)fiber, (m) matrix.  

Try this site:
Create a DEMO account, and log in.
Then, go to this page:

There you need fiber volume fraction.
To convert from weight (W) to volume (V) fraction, use Eq. (4.9)
in this textbook:

W_f = rho_f/rho_c * Vf
W_m = rho_m/rho_c * Vm  

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Ever Barbero


Structural Mechanics, Mechanics of Materials, Structural Analysis, Material Modeling (numerical, analytical), Testing (mechanical, aging, etc.) of Composites and Polymers, mainly Polymer Matrix and to lesser extent Materials Science and Processing of same. See


Working with Composites since 1983, two patents.

Fellow, Society for the Advancement of Materials Process Engineering SAMPE
Fellow, American Society of Mechanical Engineers ASME
Member, American Society for Testing Materials ASTM
Member, American Institute of Aeronautics and Astronautics AIAA
Member, American Society of Engineering Education ASEE

100+ peer reviewed papers on every major journal on composites and mechanics
Introduction to Composite Materials Design, ISBN: 1-56032-701-4,
Finite Element Analysis of Composite Materials, ISBN: 1-4200-5433-3,

PhD Engineering Science, 1989, Virginia Tech.

PhD Engineering Science, 1989, Virginia Tech.

Awards and Honors
SAMPE Fellow (2006).
ASME Fellow (2003).
Best Overall Paper Award, Combined Composite Expo’99 and ASCE Materials Conference’99, Cincinnati, OH.
Best Paper Award, 1999 ASME J. of Composites for Construction, Vol. 4, No. 4, p. 185-191.
MAE Alumni Academy Award for Outstanding Teaching, 1999.
SAMPE Faculty Advisor Award 1998.
Researcher of the Year, College of Engineering, WVU, 1996.
Outstanding Researcher Award, College of Engineering, WVU, 1992, 1994, 1996, 1997, 1999.
Best Advanced-Composite Paper Award, Composite Institute, Society of the Plastic Industry, 1994.
Outstanding Graduate Teacher Award, College of Engineering, WVU, 1992.

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