You are probably sick of chocolate by now (or maybe not), but I’m sure many of us have had more than our fair share over the last few days. In all that while though you might not have thought much about how great a material chocolate is!
A lot of engineering goes into chocolate, with many steps that have to be done just right in the production process to get anything like the tasty treats we’ve been enjoying. This is all necessary as the behaviour of chocolate can change dramatically with different processing.
For example, if you extrude it under the right conditions you can make it flexible enough to tie knots in, or, of you get the wrong structure, it will melt in your hand and not in your mouth… Indeed, chocolate even changes with time; if you’ve ever been foolish enough to leave it around for more than a few weeks, you might see a whitish layer appear at the surface. This is in fact fats, or possibly sugars, that are separating out as the chocolate structure evolves. Clever stuff indeed.
For me however, the really great thing about chocolate is how good an analogy it is for many of the more structural engineering materials, and one that is generally pretty safe to work with for demonstrations. We have been doing a chocolate impact testing demo for outreach for many years, and have adapted this for the undergraduate degrees across the Faculty of Engineering to demonstrate experiment planning and lab safety, and also for our own students to design and test composites (including other foodstuffs in the mix, not making it any tastier, but making it harder to break).
In addition, chocolate responds to heat treatment with changes in microstructure and properties, can be cast, welded, forged etc, just like many of the materials we spend more time studying.
So apologies for the bad pun in the title of this post, but I think chocolate is cracking (even if it is not used for eggs).
Dr Russell Goodall
Undergraduate Admissions Tutor