Learning Forum

[MaximilianSauer28]

Hello,

I have a bending beam of two different materials, which is loaded with a force in the middle. How can I determine the maximum bending stresses on top and bottom of the two materials? Have tried it with a path but it makes no sence, because the solution shows the same values on the bottom side of the fist and the top side of the second material.

pleas help me

 

[peteroznewman]

Are the two materials bonded together at the interface or are they just touching with frictional contact?

[MaximilianSauer28]

They are bonded together

[MaximilianSauer28]

I have to do a three-point bending test on a hybrid-bending beam made of wood and CFRP (see sketch)

[peteroznewman]

Is there a huge air gap between the strips of Pine wood?

[MaximilianSauer28]

yes

[peteroznewman]

You need to create all six pieces in the Geometry editor and use either Bonded Contact to glue them together or use Shared Topology to connect them using shared nodes.

[MaximilianSauer28]

they are bonded together

[MaximilianSauer28]

are my sketches right? I made one sketch for the CFRP & Pine wood and another sketch for the plywood. After that I extrude the sketches

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[peteroznewman]

Draw a CFRP rectangle, Extrude, Generate, New Sketch (use the button next to the sketch pull down).

For the Extrude dimension, use half the length of the beam. Do this for all extrusions.

Draw a Pine rectangle, use the P and the C to get it to align with first rectangle, only dimension thickness. 

Click on Extrude, in the Details View, change Operation to Add Frozen so you get a second body. Generate.

New Sketch, draw a CFRP rectangle, Extrude, Generate.

Draw a Pine rectangle, use the P and the C to get it to align with first rectangle, only dimension thickness. 

Click on Extrude, in the Details View, change Operation to Add Frozen so you get a fourth body, Generate.

New Sketch, draw a plywood line, but draw it a half thickness above the first four blocks, draw a second line below. Use C to get the length, only add a dimension for the half thickness distance from the existing ends.

Click on Extrude, in the Details View, change As Thin/Surface? to Yes, and Inward Thickness to 0, Generate.

In the Tree Outline, at the bottom it says 6 Parts, 6 Bodies, pick the first two Solids and Form New Part, repeat for the next two Solids.

You now have 4 Parts, 6 Bodies.  That operation created Shared Topology so the CFRP and the Pine are connected with common nodes.

Tools, Symmetry, Symmetry Plane 1, select the XY plane that you have been sketching on, and Model Type Partial Model, Generate. The makes the half length beam have a boundary condition at the center of the beam.

Close Design Modeler and in Mechanical, you will select the two surface bodies and assign the thickness to the plywood.

In Engineering Data, you must create the three materials.  In Mechanical you must assign the materials to the six bodies.

On the Connections Folder, Insert Manual Contact Region, select the two Plywood surfaces as Target and the eight end faces of the solids as Contact. Set Shell Thickness Effect to yes.

Click on Static Structural, select the end face of the top CFRP solid on the XY plane and add a Force, Define by Components in the - X direction.

Select the other end face of the bottom CFRP solid (not on the XY plane) and add a Remote Displacement and set X and Y and Rotation Z to 0 while leaving all others free. That is simply supported on a roller condition.  The Z direction is taken care of by Symmetry at the center.

 Solve.  Add a Deformation and different kinds of Stress Results under the Solution branch.

[MaximilianSauer28]

"On the Connections Folder, Insert Manual Contact Region, select the two Plywood surfaces as Target and the eight end faces of the solids as Contact. Set Shell Thickness Effect to yes."

I can not select the inner surface of the shell body. It always takes the one inside and one outside.

 

[peteroznewman]

That doesn't matter for Bonded Contact.

If it was Frictional Contact, you would have to use two separate contacts so that the correct side of the plywood could be selected.

[MaximilianSauer28]

Are there any requirements which have to be considered between the surfaces of the CFRP and Pinewood

by the way, many thanks for ur support

[peteroznewman]

The requirement is that they share a coincident face in the geometry. That allows them to Share Topology.