COMPOSITE BEAM 3-POINT LOADING SIMULATION

Modeling Process:
To design the Beam, an initial skeleton for the model was made in SolidWorks. This model was then imported to ANSYS for stacking lamina using the ACP tool. The final design has 5 sets of composite lamina layers stacked in the orientations [90/45/-45/0] on the top and bottom flange. The web consists of 1 set of the lamina stack [90/45/-45/0] which is held to the flanges through a bonding set of laminae of [90/45/-45/0] sequence. The setup is fully covered up by 2 sets of [90/0] sequence.

Dimensions of the final model:
Each lamina layer is 1mm thick. Based on the number of layers, the flange thickness is 27 mm (1.063 inches). The web thickness is constrained to a maximum limit of 1 inch in the problem. The given composite beam has effectively 21 layers of lamina accounting to a total of 21 mm (0.8268 inches). The flange width is set at the given maximum of 4 inches. The length of the beam is set to 24 inches with roller supports at 0.5 inches from each end which effectively makes the 3-point bending test on a length of 23 inches.

Simulation Based Design Substantiation:
The beam was subjected to a modified three-point bending using load block. The force exerted by the load block was simulated using a uniformly distributed load acting on the top surface of the flange at the center. This load will cause a deflection resulting in the bending of the beam. Since there are no torsional couplings here, the beam does not twist under load.

The load acting on the beam was simulated using a distributed load over the contact area of the loading block. A loading force was distributed over a contact area of the composite. This contact area was calculated from the dimensions of the loading block. For the support rollers, 2 panels were created as contact surfaces on the bottom such that the effective length of the beam between the rollers is 23 inches.

Failure was assessed based on the Tsai-Hill failure theory. The laminate was assumed to have failed when the Tsai-Hill values were greater than 1.

Failure in the composite was observed at 42200 N with Tsai Hill value exceeding 1 in bottom flange of Bottom ply:

Load applied: 42200N ~ (9480lbf)
Max Tsai-Hill value: 2.501
Failure ply: 1st surface of bottom flange (1st 90-degree ply on the bottom surface)
Maximum stress: 133.1MPa
Maximum deformation: 0.6209 mm

In the iterations conducted, a complete failure across the entire width of the 1st 90-degree ply on the bottom surface was observed. This is one of the weak areas of the beam as the load is transferred to the bottom flange over a relatively smaller thickness of the web compared to the loading block. The sharp edges cause stress concentration at this region. Since the mid plane deforms the most, it encounters maximum stresses and hence failure occurs in this region.