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# Applying Torsion to Composite Cylinder - Very high shear modulus

## Applying Torsion to Composite Cylinder - Very high shear modulus

(OP)
Hi All

I am new to FEMAP, after using Abaqus and Ansys for many years. I am modelling a fibre reinforced composite cylinder, and applied Torque to one end of the model and fixed the other end, mimicking the a torsion test. I have listed my steps here in image below.

The in- plane shear modulus of the cylinder is coming out twice it is supposed to be. And even with a different layup it is much higher than it should be. I have taken the applied moment from the cross-section end subjected to torsion and found the shear stresses and used the rotation to determine shear strain (which all sounds right). I do not know where I am going wrong.

### RE: Applying Torsion to Composite Cylinder - Very high shear modulus

Where do you measure the shear stress - at the fixed end of the cylinder ? What is your analytical solution based on ?

### RE: Applying Torsion to Composite Cylinder - Very high shear modulus

(OP)
Hey, thanks for your reply. I am using the applied torque obtained from the end under rotation and using that value of torque obtaining the shear stresses. My analytical predictions are obtained from FEMAP itself, which is obtained when feeding in the layup, and clicking on compute which used classic laminate theory to determine the in-plane shear modulus.

If I use the constraint moments, the shear modulus values will be significantly be lower.

### RE: Applying Torsion to Composite Cylinder - Very high shear modulus

Did you try using shear stresses and strains obtained directly from the results plotted by FEMAP in the middle of the cylinder ?

### RE: Applying Torsion to Composite Cylinder - Very high shear modulus

(OP)
I did try, it is giving me shear modulus of 4.49 GPa which I entered in material model as shear modulus of matrix. The predicted shear modulus was 26 GPa. I dont understand where I am goimg wrong.

### RE: Applying Torsion to Composite Cylinder - Very high shear modulus

(OP)
Hi all many thanks for your help. I have solved the problem. It was my calculation error, as the axial modulus came out just fine and shear modulus was not working, so I went back and checked my calculation. I took the applied torque for calculating shear stresses.

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