carbon and kevlar weights vs glass stiffness

[pentagram]

hi everyone, yeah i know there has been heaps of threads about carbon but I have been looking hard through this site and grafsnowboards and come up with a'lot of conflicting calculations on what weights of carbon and kevlar are equal to glass. the best i have found is,
70 gm2 of carbon = 100 gm2 glass
86 gm2 of kevlar = 100 gm2 glass
can anyone with experience and or godly knowledge of composites clear this up once and for all?
thanks

[SCHÜSS]

if you are talking about stiffness, from experience you cant do it like that because all 3 composites have different properties.

If you are talking about physical weight, then 50g/m2 of carbon would equal the same 50g/m2 of glass.

If you are talking about stiffness, then even layup position makes a HUGE difference as some composites are 'better' at different things.

I did a few experiments on just this. For eg, a wood core with one layer of carbon on top. When its cured and you flex the wood w/ carbon on top it reacts hugly different in stiffness and pop as to if you flip it over and flex it with the carbon on the bottom.

i also believe if you had the same wood core with 1layer of carbon, it would still be stiffer than 50oz of glass. if not more. My latest layup used

2layers of carbon
1 22oz triaxial glass
core
1 2oz triaxial glass
2 6oz glass
2 kevlar

and the ski flex is perfect for a race ski.

so it more matters on 'where' you put the layers and chooising what you want them to do.

sorry if i wasnt any help or confused you even more!

schuss

[davide]

By calculations and experience, glass can be replaced by carbon weighting one third, that is 400 g/m2 UD glass can be replaced by 150 g/m2 UD carbon in order to obtain the same stiffness.
This holds in tension (bottom layer). In compression carbon is only slightly better than glass, so it would be better to use a heavier frabic on top (i.e. 200 g/m2 UD carbon).
Same for biaxial and triaxial fabrics.

The best way to get a light ski is to use a light material for the core, rather than replacing carbon with glass.

[pentagram]

i have already bought some carbon and kevlar for my board. i have 200 gram/m biaxial and also 200 gram/m plain weave ( this covers 0,90 and 45,45)
my plan was to have one layer of each of these carbons to get quad axial carbon action..and using 70 gram/m kevlar to protect the carbon.
can anyone give advice on this planed layup?
thanks

[pentagram]

had put my building plans on hold for a while but now is the time,

can anyone please give me some advice on how the materials i have for reinforcement might work out.

I have 200gm m2 biaxial carbon (0,90)
and 200gm m2 plain weave carbon (45,45)
70gm m2 kevlar biaxial (0,90)

the plan was to use one of each 3 fabrics for top and bottom,

but I know that there are some people with experience using only carbon and kevlar and would really like some advice please
thanks

[pentagram]

anyone?

[King_of_the_Hill]

Carbon has a stiffnes (E) that is roughly 3 times higher than glass, however when you use less the moment of inertia (I)will lower.

But a layup as you proposed will probably work, just keep in mind kevlar wont give a lot of stifness on the top side since it doesnt work well under presseure (max tensile strength 3000 MPa max compressive strength about 400MPa)

[pentagram]

thanks king of the hill, does anyone have a good link to any online information such as glass vs carbon strengh / stiffness.

[King_of_the_Hill]

I can get you some material datatables if you'r intrested just pm me