Hi to all,
I want to know the difference between the csm, plain and twill fiberglass.
I usually use csm, woven and triaxial fiberglass in my boats but never plain and twill.
Also i use polyester resin with vacuum infusion.
The mechanical characteristics of these materials is something to puzzling me for a long time.
I appriciate if you give me some thoughts.
Regards
There won’t be a ‘real world’ mechanical difference between plain or twill weave fabrics, provided they are made with the same type of glass. E-Glass is the most common type of glass, and likely what you are using. S-glass is stronger and mechanically better, but less common. You would likely have to request S-glass in order to get it, it’s unlikely that your supplier will just be selling S-glass as standard fibreglass.
Triaxial fabrics will have slightly better performance simply because they are essentially 3 layers of unidirectional fabric stitched together at varying angles (I believe 0/60/60 is the common triax alignment). Unidirectionals have 0 crimp, so are a little bit stronger and stiffer than woven fabrics.
CSM is the weakest of the bunch. Not only is it normally quite low quality glass, so it’s mechanical properties are lower to begin with, but it is also made up of very short strands of fibres. Where the fibre ends it no longer provides any strength, so the laminate is weaker because of that. The advantage is that the fibre orientation is completely random, so it is easy to build strength in virtually all directions.
Thanks for the infos.
You opinion for boat building is to use more plain or twill rather than csm ?
Tnx
My experience is in automotive, boats are a bit of an unknown to me.
That said, I would think material choice would come down to requirements and budget more than anything else.
If you’ve been using CSM with success, there’s no problem in using it. From an engineering standpoint, CSM will always be weaker, and heavier due to being more resin rich. Woven, unidirectional, triaxial… all have known grains (the warp/weft) that carry the strength. CSM sacrifices this for approximate strength in all directions, but no guarantee of which direction (or for that matter, section of the structure) carries the most strength.
As for the weave of the fabric, these do have some tradeoffs, but not as significant as they sound. The more crimps, generally the more drapable the fabric is, but the more resin rich it will be. This is why a harness weave and twill generally drapes better than a plain weave. However, the loss of strength/weight is not enough that most people will be concerned with it.
Although I’m new to vacuum infusion myself, my understanding is that woven fabric is better for infusion due to there being a more direct path of resin to flow, even though it will use less resin.
With all that said, CSM has it’s place, and many quality parts are built with it. No need to change it unless it’s going to fix a problem or see a direct benefit.
Your fabrics will always have far better resin/fibre content when compared to CSM so more strength and much less weight.
For glass fabrics hand laid you will use about equal weight in resin.50:50
For glass fabrics vacuum infused you will get about 32% resin content. 68:32
CSM is usually hand laid and this will use double its weight in resin. So it’s 66% resin and 33% fibre. Heavy!
But CSM is typically used for other reasons.
It’s cheap.
It’s easy to use and place in moulds as it stretches when wet out.
But finally the best reason to use CSM is it acts as a surface barrier to prevent gelcoat print through from fabrics! and resin shrinkage. So you just lay down a single light layer to do this (225gm or tissue or both). A little extra weight but a better cosmetic finish.
Twill has less warp then plain, but is stil more drapable.
You’re right, I had that backwards. Thank-you for the correction.