Bonded stiffeners

Construction. Polymeric materials such as adhesives, sealants, and composites have been used considerably in the last several decades for the construction, repair, and rehabilitation of our transportation infrastructures. Even though most processes were experimental until recently, they have evolved to the point where many are now standardized and well accepted. Table 1.6 hsts several common applications for advanced polymeric materials (as well as the polymeric resins that are most commonly employed). In the construction or repair of roads and bridges, epoxy adhesives have primarily been used for bonding concrete and for bonding stiffening members or repair structures to degrading concrete facilities. 

Polarity and hydrogen-bonding stiffen the polymer molecule, improving mechanical properties and especially resistance to hot water. This improvement is useful in household products, autos, and appliances. 

Figure 16.36 shows the applicafion of EMIS for the detection of 20 mm long delamination on a 2 mm thick L-section bonded stiffener [82] PWAS a2, which is placed in a zone proximal to the delamination, displays new resonances associated with disbond vibration at 350 and 510 kHz. In the same time, these new resonances are not present in the spectmm measured by the witness PWAS transducers al and a3, which were placed on the same stiffener but some 70 mm away on either side of the disbond. The fact that the al and a3 spectra are almost identical confirms the consistency of the EMIS method. 

The performance of curtain walling wall panels fabricated with bonded and with bolted channel section stiffeners was compared. Under simulated wind pressure, the bonded stiffeners accommodated gross panel deformations representing several times the design requirements. 

Harvey, W.J. and Vardy, A.E. Bonded Stiffeners for Steel Bridges, Proceedings of the 27th Conference on Adhesion and Adhesives, City University, London, March 1989. 

When thin members are bonded to thicker sheets, operating loads generally tend to peel the thin member from its base, as shown in Fig. 9.23. The subsequent illustrations show what can be done to decrease peeling tendencies in simple joints. Often thin sheets of a material are made more rigid by bonding stiffening members to the sheet. 

PU, polyester or epoxy adhesives and sealants for naval construction (bonding deck to hull in yatchs, bonding stiffeners to hull in larger ships). 

The frequency of lattice vibration shift from the bulk value of 7.1 to 11.6 THz, implying bond stiffening. 

The main structural component of the SR.N4 (British Hovercraft Corporation) according to Powis (1973) is a large sandwich panel 40 m long, 23 m wide and about 1 m thick. The top and bottom skins of this sandwich panel are made of 2 5 mx 1 25 mx 37 mm sandwich panels which are bolted to an egg-box structure made from aluminium shear web with bonded stiffeners. The skin panels are of 6 4 mm and 3 2 mm cell aluminium honeycomb made from foil 0-05-0-076 mm thick. The higher density core is used in the more highly stressed areas. The superstructure of the craft is composed of two vertical beams running fore and aft, which are fabricated from this aluminium sheet with bonded stiffeners. The roof is one unsupported span between... 

For small boats (up to 24 m long) design and scantling rules have been assembled in a recent set of ISO (International Standards Organisation) documents. Part 6 of this set is entitled Small Craft-Hull construction and Scantlings - Structural arrangements and details (ISO 12215-6 2008), and includes a section on bonding. Bonded stiffener, bulkhead, and deck-hull assemblies are considered, Fig. 48.1. 

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