Originally Posted by
vettracer
...well sure. Your lacrosse stick was made from thermoplastic. When cold, it got close to the glass transition temperature causing a large change in material properties.
Carbon bicycles are made from thermoset polymers which are already well below their glass transition temperature even in Phoenix in the middle of summer. They do not go through a significant change in material properties in freezing weather. Carbon composites routinely operate at temperatures below -40 in aircraft.
Originally Posted by
vettracer
CroMo Steel is good down to about -50C. Aluminum and Titanium don't have embrittlement problems at survivable temperatures for humans.
Originally Posted by
vettracer
Here is an example of the impact strength of CroMo steel at low temperatures. These steels are susceptable to low temperature embrittlement though the exact shape of the curve will vary by alloy composition. Other steel alloys with nickle alloy like some stainless grades do not show the embrittlement phenomena.
Another real, live materials scientist/engineer on this thread, cool.
DBTT, ductile-brittle transition temperature...this is bringing back memories from my undergrad classes.
For others on this thread, the sudden-onset ductile-brittle transition is an interesting property of some metals/alloys. Essentially, the material undergoes a sudden transition from ductile to brittle at a certain temperature. This change from ductile to brittle also means there is a sudden, large drop in the toughness of the material.
It was largely an unknown phenomenon up until about the 1940s. It was actually a major problem with the so-called "Liberty ships" that sailed in the northern Atlantic Ocean during WWII. The metal alloys behaved perfectly at ambient temperatures when tested during construction, but would undergo a sudden, substantial transition from ductile to brittle at a certain temperature, the DBTT. The problem in those days was that the DBTT was higher than the temperatures of north-Atlantic waters, so these ships suddenly became very brittle when they sailed out into cold water, leading to catastrophic failures. This is one of the issues that lead to much of the study of metallurgy (and later materials science) as we know it today.
Nowadays, we know and understand a lot more about the behavior of materials, so to a competent engineer, things like service temperature are well accounted for.