Torsion can be prominent in most of the experiments that you do. The goal is to cut down the presence of torsion in the experiments as much as possible.You don't want a lot of torsion because it will make the staw or paper fail sooner and give you less accurate results. And this is how you go about having as little torsion as possible for the different experiments:

Compression: In the compression experiment you have to be very carful as to how you place the paper roll and the straw into the jig or there will be too much tension. Too get the least torsion possible, try to get the straw and the paper as centered as possible. But it will ultimatly fail because of torsion and shear

Bending: To reduce the effects of torsion in this experiment, try to not let the paper roll bend by making sure that the two supports on each side of the roll are even hight and the the wire pulling down on the roll is in the middle.

Tensile:In the tensile test if there is too much torsion will accelerate the breaking of the paper and straw. So if the straw starts to bend, steady the weights from swinging and when put them on carfully so the they dont twist the straw.

Elasticity: In this test torsion is not that big of a problem since ruberbands will twist easily but it may effect your results so follow the same precautions as in the tensile test.