It’s easy to get excited about the visible breakthroughs in 3D printing – the 3D printed medical devices, the architecture, the art. What we don’t think about as often are the seemingly mundane and unseen applications that 3D printing is also changing – but they’re just as important. Foams, or cellular solids, are hidden everywhere around us – in our walls, our cars, our electronics. They’re a major component in insulation, shock absorbers, and flotation devices. Foams are great, frankly, and material scientists at Lawrence Livermore National Laboratory may have found a way to make them even better through additive manufacturing.
Traditional foam manufacturing processes result in foams with non-uniform consistency, with the cells making up the material greatly varying in size, shape, and connectivity. They still serve their purposes, but the scientists in LLNL’s additive manufacturing lab have found that 3D printing can smooth out those issues and create uniform foam structures. Sounds great – let’s use that instead! Not so fast – like anything else, the new foams have to be subjected to a number of tests before they can be marketed. Mostly, the scientists needed to assess the long-term mechanical stability of the foams – how well and how long will they hold up, especially when subjected to repeated stress like in shock-absorbing cushions?
Turns out they hold up pretty well. The research team conducted a series of accelerated aging experiments in which both the 3D printed foam and traditionally manufactured foam were subjected to high temperatures and constant compression to approximate the amount of stress the foams would withstand over a course of several years. The foams were monitored over the course of a year or, in some cases, longer. At the end of the test period, the researchers discovered that the 3D printed foam held up, mechanically and structurally, for longer than the traditional foam.
To determine why the 3D printed foam was so much more resilient, the scientists X-rayed both materials and found that the traditional, or stochastic, foam showed more widely dispersed stress fractures than the 3D printed foam – unsurprising, considering the stochastic foam’s varied consistency. The traditional foam’s most extreme areas of stress were also much higher than those of the 3D printed foam.
“3D printing of foams offers tremendous flexibility in creating programmable architectures, customizable shapes and tunable mechanical response,” said Amitesh Maiti, a computational physicist at LLNL and the lead author of the foam study. “Now that our work strongly indicates superior long-term stability and performance of the printed material, there is no reason not to consider replacing traditional foam with appropriately designed 3D-printed foam in specific future applications.”
The full research paper, which you can read here, states that the work is not nearly finished, however.
“Finally, we would like to point out that that the results presented here compares the aging of a stochastic foam with that of an AM foam of a very specific architecture,” the paper concludes. “We acknowledge that there may be better performing AM designs, including other optimal 3D designs that we are yet to explore. Identifying and testing such novel micro-architectural designs is an area of future work.”