Double strap joint

Nguyen, T.C., Bai, Y., Zhao, X.L., and Al-Mahaidi, R. (2011) Mechanical characterization of steel/CFRP double strap joints at elevated temperatures. Compos. Struct., 93, 1604-1612. 

Double-lap joint outer adherends, or double-strap joint straps... 

Single- and double-lap and single- and double-strap joints have stress concentrations at the ends of the overlap when loaded with in-plane loads. These are the most probable locations for the failure initiation. A t3rpical shear stress distribution is shown in Figure 5.27. 

P(l) This design procedure shall be applied only to tensile shear loaded single-and double-lap and single- and double-strap joints. 

For double-lap and double-strap joints calculate the maximum adhesive shear stress (for notations see Figure 5.38) ... 

P(3) In-plane shear loaded double-lap and double-strap joints shall be designed using the corresponding equations for tensile shear loaded joints and using the parameter conversions of Table 5.6. 

It is assumed that the method described for double-lap joints can be applied also to double-strap joints. 

A typical laminated joint is a butt joint on to which doublers are laminated, the result being a double-strap joint. The following features distinguish this laminated joint from the corresponding adhesively bonded double-strap joint ... 

Figure 4 also shows that maximum loading densities of single-lap and single-strap joints are very close to each other. This is also true for double-lap and double-strap joints, as can be seen in Table 6. These results indicate that lap and strap joints may be treated using similar design principles and design procedures. 

Double-lap and double-strap joints can be treated identically. 

Flexible Plastics and Elastomers. Thin or flexible polymeric substrates may be joined using a simple or modified lap joint. The double strap joint is best but also the most time-consuming to fabricate. The strap material should be made out of the same material as the parts to be joined, or at least have approximately equivalent strength, flexibility, and thickness. The adhesive should have the same degree of flexibility as the adher-ends. 

Figure 31. The single-strap joint (a), the double-strap joint (b), the tapered-strap joint (c), and the tapered-strap scarf joint (d).

The experimental validation presented later is for two geometrically identical wet lay-up CFRP/steel double-strap joints (refer to Fig. 10.10) with their measnred inner adherend s thickness (fi/steei) equal to 4.85 mm. Adhesive/matrix (i.e. Araldite 420 epoxy resin) is the same for both specimens however, they are fabricated with different CF plies (i.e. NM and UHM) and tested under different exposure temperatures (i.e. 0°C and 20 C), respectively. Figure 10.12 portrays the assumed thicknesses for the... 

For joint capacity predictions of the CFRP/steel double-strap joint model of Fig. 10.15, the precise manner in which the failure criteria are applied and the consequent stress predictions extracted can be summarized as follows (Al-Shawaf, 2010) ... 

Al-Shawaf A (2010), Characterization of bonding behaviour between wet lay-up carbon fibre reinforced polymer and steel plates in double-strap joints under extreme environmental temperatures , Doctorate PhD thesis. Monash University, Melbourne, Australia. 

Eqs. 2-6 have been formulated for one-sided bonded joints. For double-lap or double-strap joints, there needs to be some self-evident modifications. The easiest way to approach this is to say that t2 refers to one of the two splice straps and that t refers to halfihe inner adherend thickness, so that one is dealing with the load transferred through one bond layer. 

Composite repair configurations (a) singie strap joint (b) double strap Joint (c) scarf joint (d) step joint... 

For double lap and double strap joints, analytical analyses are attributed to those for asymmetric joints by using the variable transformation discussed in Luo and Tong (2002) for the host beam with the piezoelectric patches bonded on the top and bottom surfaces. The analysis for asymmetric joints will be presented in the next section. 

Single- and double-lap Joints, single- and double-strap Joints, peel Joints and cylindrical Joints... 

Recessed double strap joint Very good - expensive machining... 

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