Other Bonding Geometries of Interest: L – and E-types

U-type and T-type bonding geometries can be considered as baseline geom­etries which can be used for the derivation of conclusions for other geometries; for example, L – and E-type bonding geometries. The L-type bonding geometry can be interpreted as a modification of a U-type bonding geometry by eliminat­ing one of the two side regions. Figure 19 presents experimental results for this bonding geometry, confirming close relationship between U-type and L-type bonding geometries. The mechanical characteristics are very similar; thus, a similar test campaign with degraded bonding was not taken into account. In the view of durability, L-type bonding geometries are assumed to be less favor­able than U-type bonding geometries as one of the two exposed surfaces of the bonding geometry is located at the highly loaded front region. Depending on whether this side of the bonding is exposed to environmental attack, the highly loaded front region might fail faster due to these conditions. In this case, the size of the side region will determine the actual load capacity.

Figure 20 shows the stress levels for front and side regions in the usual way, confirming the above-mentioned statements. While the stress distribution with respect to the side region is qualitatively in good agreement with the side region of the U-type bonding geometry, the stress distribution in the front region and especially at the exposed surface shows similarities with the front region of the T-type bonding geometry.

Thus, it can be concluded that the exposed surface at the front region (label C) is the weak point of the L-type bonding with respect to durability in case both surfaces are exposed in the same way to the environment. Otherwise, it is recommended, if possible, to place the side region of the L-type bonding geom­etry towards the more aggressive environment in order to shield the highly loaded front region.

The E-type bonding geometry can be considered as an extension of the


FIG. 20—Maximum principal stress distribution in L-type bonding, Lf=30mm (1 N/mm2=1 MPa).

U-type bonding geometry by adding the inner flange or alternatively as an ex­tension of a T-type bonding geometry by adding two outside flanges. For the E-type bonding geometry, no experimental tests were performed. Nevertheless, it can be hypothesized that the mechanical behavior is similar to a superposi­tion of U-type bonding and T-type bonding. In terms of durability aspects, the E-type bonding geometry is assumed to correspond to U-type bonding geom­etries. These assumptions are supported by Fig. 21 showing the stress distribu­tions for the E-type bonding geometry. The stress distribution obtained with respect to the outer side region is in qualitative agreement with that of the U-type bonding geometry, while the inner flange loading is in qualitative agree­ment with the corresponding behavior of the T-type bonding geometry.