I am trying compare metals, mostly stainless steels, with plastics and
I've noted that modulus of elasticity often appears on metal data
sheets and flexural modulus often appears on plastics data sheets. Is
it acceptable to compare values for flex mod with those for elastic
mod, or is that like comparing apples and oranges?

Thanks,
Leigh

It's more like comparing two varieties of apples.

Elastic modulus is a fundamental material property of both metals and plastics
and can be estimated by either tension, flexural or other mechanical tests.

Values derived from flexural and tensile testing can be compared legitimately
and this may be useful for a broad brush examination of possible material
selections for a design. However, for more exact comparisions, it is desirable
to use the same method. That is "Granny Smith to Granny Smith".

RT

You can compare mechanical properties of steel with plastics, for design
purposes, but you also need to know and consider the conditions at which the
various properties were determined, which can vary quite a lot! Also,
mechanical properties of plastics are much more affected by "environmental
factors", like humidity, temperature, chemicals etc., than metals are.
Within the normal temperature range plastics are used in, e.g. -50°C -
+250°C, the modulus and strength of plastics change dramatically, whereas
steel is virtually unchanged ....