The term “flexible” is not correct since flexibility implies deformation under a relatively low load, and what is being measured here is the deformation at which failure occurs, not the deformation at a particular load; nor is the term “resilient” correct, since resilience refers to elastic deformation (i.e. it will reverse itself if the load is released) whereas the transverse deformation measured by BS EN 12002:2002 could well be plastic (i.e. permanent)
This particular S2 adhesive may be thought of as being less flexible as it takes a bigger force to distort it. It is possible for an S2 adhesive to require a substantially higher load to achieve a given degree of deformation than an S1 adhesive.
The terms and differences you’re making in your statement are quite correct when addressing the mechanical properties of materials and adhesives. Let’s break down your points:
Flexibility: You correctly pointed out that flexibility usually means deformation under a relatively low load. In materials tests, flexibility often refers to the ability of a material to deform elastically (bend or stretch) under a load but return to its original shape when the load is lifted. The word “flexible” is not acceptable when describing materials or adhesives that deform plastically (permanently) rather than elastically.
Resilience: Resilience indeed refers to the ability of a material to bend elastically and then return to its original shape when the load is removed. This trait is important for materials that experience cyclic loading or need to keep their basic form. If a material experiences plastic deformation and does not return to its original shape, it’s not called robust.Flexibility and Deformation
In the context you gave, the difference between S1 and S2 adhesives based on the load needed for deformation is a valid way to describe their behavior. S2 adhesives would require a higher load to deform to a certain amount, which means they have a more stiff or less flexible behavior compared to S1 adhesives. However, it’s important to note that these terms are relative and should be used with an understanding of the specific setting and testing standards (such as BS EN 12002:2002 in your case).
In summary, the words “flexible” and “resilient” have specific meanings in the context of material science and mechanical testing, and your description of their suitability in describing the behavior of S1 and S2 adhesives is correct Flexibility and Deformation