MIT 3D Prints Tough, Bone-Like Composite

A team at MIT has 3D printed bone-like composite materials on the Objet Connex500 multi-material printer.

The test setup includes an Instron 5582 Universal Testing Machine with an Instron 100 kN static load cell. Shown here, a sample of the bone-like material is clamped in place before being stretched to make it fracture.   (Source: M.J. Buehler/MIT)But this wasn’t just any old multi-material model using the Objet polymers. They were samples printed to test a computational model the engineers had created, based on three different bone-like, biological composite structures they designed.

The structure of mineralized materials such as bone itself, as well as the structure of seashells and certain marine sponges, combines soft materials with stiff materials in complex arrangements that have superior fracture mechanical properties. We’ve covered similar materials before, such as the entirely new family of composites invented by ETH-Zurich materials scientists that mimic the way an abalone shell’s structure aligns strong, stiff elements within a softer matrix.

Another composite modeled after a biological original is the complex fish scale architecture we told you about that could be mimicked to provide flexible composites with a hard ceramic surface for applications like body armor or prosthetic devices. That architecture’s very hard exterior protects a tough, flexible internal structure that helps the scales of the Amazonian Arapaima gigas fish resist razor-sharp piranha teeth.

But using a 3D printer to print out test samples for verifying the models is a new idea. The MIT team, led by professor of civil and environmental engineering Markus Buehler, designed three different synthetic composite materials that emulate bone, bio-calcite, and a rotated bone-like geometry. All of them take advantage of the combination of stiff and soft materials typically found in composite structures, but their topologies vary. One of the project’s main objectives is to show that it’s possible to design materials that have specifically tailored fracture mechanical properties, using computational models, and then make those materials using 3D printing.

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