**3.2 Section "B," "C," "D," and "E" FEA results**

Sections "B," "C," "D," and "E" showed a considerably inferior performance to section "A." However, the surface area of their yoke plates and their overall height (with the clear exception of Section "B") was considerably less than that of section "A." The substandard performance of these sections can be directly associated with the change in curvature of the composite winding due to the change in the heightto-length ratio for the overall cross section. As this ratio increases (height < length), the curvature radius decreases, and thus, stress concentrations appear in the

#### **Figure 6.**

*Stress results for ellipsoidal section design configurations: (a) configuration 1, (b) configuration 2, (c) configuration 8, (d) configuration 9, (e) configuration 13.*

composite winding. However, a small length-to-height ratio (height > > length) similar to Section "B" is also undesired, as the stress in the side plates increases considerably.

As is the case with section "A" results, a noticeable lack of stress near the yoke plates interface is observed in the results for sections "B," "C," and "D". Likewise, the stress magnitude on the side yoke plates is less than that of the main yoke plates. A non-horizontal angled cut contact interface could have been implemented for

**33**

**Figure 7.**

*Stress results for: (a) section "B," (b) section "C," (c) section "D," (d) section "E".*

*Sustainable and Efficient Hydroforming of Aerospace Composite Structures*

these sections, however, the stress on the composite winding is well above its limit in all sections, and thus, the angled contact interface would've been of little use for these configurations as they were proposed. The results for these sections are

The section E variants appeared to be the ideal candidates for an optimized designed. This was not the case, as the E section proved not to be strong enough to withstand the applied pressure load. The failure mechanism was primarily located in the composite winding, at the inner surface of the corner rounds. To reduce the stress at this location, the corner radii must be increased, although to achieve this, the height of the yoke plates must be increased, which represents a step back

*DOI: http://dx.doi.org/10.5772/intechopen.81505*

**3.3 Section "E" variants FEA results**

presented in **Figure 7**.

*Sustainable and Efficient Hydroforming of Aerospace Composite Structures DOI: http://dx.doi.org/10.5772/intechopen.81505*

these sections, however, the stress on the composite winding is well above its limit in all sections, and thus, the angled contact interface would've been of little use for these configurations as they were proposed. The results for these sections are presented in **Figure 7**.
