Tension 170 GPa (60% fiber in volume)

Compression 140 GPa

Yes, those are Elastic modulus.

From Toray web-site :

Typical "HR" (high resistance) fibers are T700S, modulus 230 GPa, strenght 4900 MPa. At 60% fiber content your composite should have a modulus close to 140 GPa, strenght of 2900 MPa.

What I use is indeed "IM" (intermediary modulus) fibers, modulus 290 GPa, strenght 5500 MPa.

Modulus and strenght (tension) of composite we get are consistent with the fiber content.

But few talk about compression properties. As said, compression modulus is a little lower, and compression strenght is a lot much lower than in tension.

For the fiber I use, compressive strenght is only in the 700 MPa range for the composite (60% fiber content).

If we go back at my design practice :

For + G loads, the upper spar cap (compression) has 1,2 the cross section of the lower spar cap (tension). I do this because of the modulus difference, not the strenght!

Max elongation strain in the spar caps it thus the same (and minimised for the shear web), the neutral fiber is at the middle of the spar.

Because of the difference in modulus, max stress in the spar cap that is in tension is 1,2 that of the one in compression.

My design criteria is only the compressive strength : 700 MPa. It means that max stress in tension is only 840 MPa when this material could probably reach 3300MPa (5500 MPa x 60%).

Of course, I check - G loads and deflections, but it all works out with what I do for the + G loads.

This is at ultimate load = 2,625 limit load in my case. So at limit load, stress are far under the 400 MPa for fatigue according to CS-VLA.

I heard of some sailplaine manufacturer using now "HM" (high modulus) fibers.

HM fibers have lower strenght in tension, but not so much in compression, and high modulus is a big help to reduce deflection and minimise the effect on the shear web. So spar caps an shear web can be thiner with this material (for gliders, probably no gain for low aspect ration planes)

High aspect ratio / very thin profile wing are possible at lower weight (GP gliders if I recall correctly, so light that they are eligible as French ultralights).