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Composite Materials/small clarification on how to make equal mixture


QUESTION: hi sir this is vasant doing project on COIR FIBRE REINFORCED VINYLESTER COMPOSITE...i want to put increasing weight percentage of coir to check where exactly is it shows optimum strength to do so i should how i am adding coir to prepare a composite..mould size 150*250*5 if i want to put 10% of many grams of resin and coir must be added to prepare a composite...resin-1.05g/cc,coir(treated)-0.22g/cc

ANSWER: Hi Vasant,

Please refer to link below;

If your dimensions are in millimeters, the final volume of the composite panel is;

187.5 cc

Of this, 18.75cc should be coir (equals 4.125gms) and 168.75cc's should be resin (equals 177.18gms resin).

This is a VERY LOW fibre volume fraction and most composite items aim for approximately 50% fibre depending on which methodology you use. Prepregs generally are around 65-75% fibre, hand layup with polyester or vinylester is around 40-50% fibre.

Hope this helps,


---------- FOLLOW-UP ----------

QUESTION: thanks for your previous suggestion if i don't know the coir    ( treated particulate) density at that time how can i add interms of percentage .give me a suggestion how to add coir without knowing its density


I'd suggest using weight fractions rather than volumes, just weigh your resin and coir and aim for a 50:50 mix by weight of each - much easier to use weights than densities.

If you really want to stick to density, make up a trial panel, weigh out the resin input, once cured, conduct a burn test or strong acid reduction to remove the resin, then re-weigh and establish the volume fraction...

Hope this helps,

---------- FOLLOW-UP ----------

QUESTION: please don't mind i m asking again and again...i want to do in weight fraction only... please give one example taking my mould size as example and my final thickness of each weight fraction samples should result 5mm only..i know only exact density of resin and i don't know about coir..187.5*1.05=197gms of which 50% means 98.5gms but i don't about coir hence unable to proceed further...

If your panel is a volume of 187ccs, and your resin density 1.05gm/cc, then a SOLID RESIN casting in that size would weigh 197gms.

I suggest you use 93.5gms of resin and 93.5gms of coir and compress the laminant in a press calibrated to give 5mm thickness.  This equates to a 50:50 resin/fibre mix by weight, use the same calculation to get different resin/fibre mixes...

Hope this helps,

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andy mackay


Composite fabrication and testing, plug and mould design & build, surfacing materials, gelcoats, resins (epoxy, polyester, BMI, urethane) GRP, FRP, carbon, aircraft and marine composites, infusion techniques, Light RTM methodology, troubleshooting materials and process engineering.


11 yrs experience with aeronautical, marine and bathroomware composites.

Royal New Zealand Air Force Advanced Composites Course BCA Victoria University, Wellington, 1995

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Aeronautical, marine and bathroom ware composite cmanufacturing.

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