The Strength of Lego

Lego_1
Capped and Uncapped (2×1 brick) Lego specimens before compression tests

Had an absolute grand time crushing Legos with Hailey Todd and the virtual ventures summer camp at Carleton University this week. Thought Id pass on some of the results we observed. Unlike the previous study conducted for the BBC where only one Lego block type was tested, we really wanted to understand what happens with Lego under a realistic building configurations and loading scenarios. So we took typical Lego blocks of 1×1, 1×2, 1×3 and 1×4 brick sizes and tested them in a loading actuator with compressive displacement control (mm per minute).

What we observed was that as the size increased so too did the ability to carry load (see graph below). Though it was not proportional to the added stud-brick for each block. We did not cap the Legos because we wanted to see the full effect. Basically the failure mechanism is as follows, the test begins with load being applied and the Lego brick ‘stud’ is pushed into the block giving a flat loading surface along the top of the block, there is a small elastic phase and then we begin to crush the Lego block (its peak load). Later we did cap the Lego and saw some interesting differences in peak load and failure pattern (see below).

lego results
Elementary school students as part of the virtual ventures summer camp at Carleton crushed Lego to introduce them to how building materials behave under load. An unexpected non-proportional trend in load increase with brick area increase was observed.

We opted to use Lego as a teaching example as its a relatable building material to youths. I think its a gate way to show them just how strong materials are when you can relate them to the day to day lives, obviously we get them hooked there, and progress to crushing concrete and breaking steel much after.

Lego_2
After testing the 2×1 brick Lego. The uncapped Lego failed at 4.2 KN; whereas the capped lego failed at 3.7 KN. Both blocks terminated with the same deformation level in mm. Not the different failure mechanisms are because the load is applied differently throughout the lego.

How I play with Lego grown up

Research Institute by Lego
Research Institute by Lego

Last month the company Lego released their Research Institute set (conceived by geoscientist Ellen Kooijman to promote science careers for women). The set features a woman chemist, a woman astronomer, and a woman archaeologist. The set sold out on the first day (online and in-store).  I managed to pick up a set though to support the message of promoting women in sciences. The set is challenging and fun. However, I wish they would have included a woman fire engineer in the set (they did propose to include an electrical engineer in the concept stage of the set and arguably the chemist could be considered a chemical engineer). However,  I can modify and create. Maybe I will re-create a scene where one of my favorite engineers of all time, Margaret Law, performs fire experiments as she did in the 1960s at the Fire Research Station (future blog entry).

Vintage fire hall by Lego
Vintage fire hall by Lego

I find there are a lot of engineers and architects I come across (men and women) who are embracing Lego sets these days. Quite often when I go into offices, I always see the  Lego Architecture sets displayed on the book shelf’s of my colleagues.  These sets are great for stress relief after a hectic day. They are great to ponder things over. And they are visibly pleasing in the corner of an office. These sets are no longer merely childern’s toys, but something educational for all ages. I take things further though. Recently I purchased the 2200 plus piece vintage fire hall set (naturally – vintage and fire) and began assembling it (pictured) . As a scientist, I question;  ‘What makes my Lego fit together so well?’ So a while back I decided to investigate just that using a Scanning Electron Microscope.  You may remember this from a previous blog where I challenged the reader to identify several materials (concrete, a steel and a plastic- the ‘plastic’ being lego) as mystery Scanning Electron Microscope images. For the Lego, I wanted to measure out the precision of a Lego piece to the micro-metre and get an idea just how snug they connect (pictured below) and what was going on at the microscopic level of these tiny interlocking bricks.

Mystery #2
Lego at 800 x
Lego at 57x. The gray scale is typical of unprocessed SEM imaging
Lego at 57 x

The lettering was most interesting (the letter E is blown up and pictured left). But in general the indents on the piece were precise to the micro-metre. I have been told that the tolerance of Lego is actually up to 2 microns.

Now things I wonder next. Could having too many Lego in a home be a fuel load hazard for a fire?  Giving that Lego is said to be made of Acrylonitrile Butadiene Styrene (anything with sytrene can be nasty toxicity wise when heated) I think I would rather avoid doing any high temperature tests for now. Instead, I could look into the compressive strength of Lego answering how tall can I make lego….but that has been done.

I guess some toys we never grow out of….