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Impact Tests


The mechanical properties of adhesives and the joints strength require specific tests. Indeed, since polymers are, in general, sensitive to the strain rate they undergo, different phenomena can be induced when a load is applied abruptly. Under such a condition, usually the adhesive tends to react to the deformation with higher stress and lesser ductility, which cause higher resisting loads but lower absorbed energy. This is why the common standard impact tests for adhesives, involving bonded blocks or strips, aim at measuring the energy required to break the bond.

However, since this result is not sufficient to characterize an adhesive, other types of tests have been introduced to obtain a deeper insight. Different types of specimens (samples of bulk adhesive, lap joint, butt joint, double cantilever beam) and test rigs (pendulum, falling weight, hydraulic actuator) have been adopted in many works to measure the properties of interest. The fracture energy, typical