Having studied Metallurgy BITD of an engineering college background, its surprises me how this little known fact is ignored by MTB designers. Klein frames were notorious for cracking over here, particularly the later Trek ones, but yet there was little of this reported in the US. I have some graphs somewhere of the flex, Strength to destruction, and fatigue life of various materials, across a wide temperature range. Incidently Graphite n Glass fibres long with the majority of common bondings resins, also lose a lot of their strength and ability to flex at lower temperatures
Unlike steel and Titanium which lose little. The engineering requirements for a hard tail are totally different to a full suspension bike, may seem obvious, but many designers still apply similar designs to HT and FS frames. The main reason why Aluminium became popular was because the Taiwanese are brilliant at working it, and hopeless at working/welding steel.