Crash suitable adhesive

Adhesive curing starts from the outside and moves inwards. As the cured skin becomes thicker, the retention strength increases until it meets the requirements mandated by the FMVSS regulations. Due to the highly viscous nature of the adhesives, a thin cured skin is often sufficient to fulfill the needs. The principal characteristics of crash-suitable adhesives are strength and energy absorption (Fig. 73). 

Failure of a lap shear sample with a crash-suitable adhesive... 

The diagram of an impact peel test in Fig. 46.13 shows the difference of a crash-suitable adhesive in contrast with a very good structural automotive adhesive. 

For achieving passive safety, other elements are important besides the choice of adhesives. It is important to mention that the windshield is also designed to have crash-suitable behaviour. 

This section focuses on crash-suitable performance and safe-drive-away times for adhesive systems. These issues are significant for the design of mechanical proper-hes which ensures that the vehicle can be used as quickly as possible after repair. 

Crash resistance should ideally be dependent only on adhesive consistency and independent of reactivity. In an optimum situation, crash suitability would not depend on climate. 

Crash suitable direct glazing adhesives were formulated in several ways. The applications are ... 

The first peak of the curves is the initial peel resistance and the jagged curve gives the average value of the impact peel strength. Whereas the standard structural adhesive ends after 15 ms with an average peel force of 400 N, the crash-suitable one withstands for almost 20 ms... 

Vehicle repair techniques, overseen by the insurance industry, are also being developed for bonding sheet steel panels. Epoxides and polyurethanes are used, and the benefits of using adhesives include the need for access only to the outside surface of the repair area as well as overall cost and time savings. Crash and impact tests have confirmed the suitability of such repairs as well as highlighting, as with new build operations, the need for judicious use of tack welds or rivets. 

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