A team of researchers from Purdue University, Cornell University and Case Western Reserve University is drawing inspiration from bones to make stronger, more resilient 3D printed structures for buildings, aircraft and more. The researchers have recreated a specific beam structure found within natural bone that provides strength and lifelong wear resistance using 3D technologies.
In construction, beams are used to support structures from the inside, providing long-lasting load bearing capabilities. It turns out, our bones function similarly. By creating bone-inspired beam structures using 3D printing, the research team believes it can produce lightweight 3D printed materials which could have applications in building, aircraft and other structures.
“Bone is a building. It has these columns that carry most of the load and beams connecting the columns,” said Pablo Zavattieri, a professor in Purdue’s Lyles School of Civil Engineering. “We can learn from these materials to create more robust 3D printed materials for buildings and other structures.”
Natural bone owes most of its strength and durability to a porous structure known as trabeculae, which is made up of interconnected vertical plate-like struts and horizontal rod-like struts, which function similarly to columns and beams. Bones with a higher density trabeculae are stronger and more resilient, while less dense bone (caused by aging or disease) become more fragile.
In their study, the researchers discovered that the horizontal struts in bone were primarily responsible for fatigue resistance, while the vertical structs were more related to stiffness and strength. This understanding varies from commonly held beliefs about trabeluae.
“When people age, they lose these horizontal struts first, increasing the likelihood that the bone will break from multiple cyclic loads,” explained Christopher Hernandez, a professor of mechanical, aerospace and biomedical engineering.
From body to buildings
The research is not only relevant to our understanding of the body, however, as it could be applied to the construction industry. As 3D printing in construction continues to gradually advance, 3D printed internal structures could play an important role in producing strong and resilient homes.
By integrating a bone-inspired architectural structure into the cement as it is printed, construction features such as walls can be optimized.
To test the theory of trabeluae’s horizontal struts, Zavattieri’s lab designed 3D printed polymer structures with trabeculae-inspired geometries. Simulations of these structures demonstrated how crucial the horizontal beams were in fatigue resistance.
Adwait Trikanad, a co-author on this work and civil engineering Ph.D. student at Purdue, said: “When we ran simulations of the bone microstructure under cyclic loading, we were able to see that the strains would get concentrated in these horizontal struts, and by increasing the thickness of these horizontal struts, we were able to mitigate some of the observed strains.”
Physical tests were then conducted on the 3D printed polymer structures, which reinforced the simulation’s findings. Moreover, the researchers determined that the thicker the horizontal struts, the longer the polymer samples would last—all without adding substantial mass. A beam increased by about 30% reportedly resulted in a material that could last 100 times longer.
“When something is lightweight, we can use less of it,” Zavattieri explained. “To create a stronger material without making it heavier would mean 3D printed structures could be built in place and then transported. These insights on human bone could be an enabler for bringing more architected materials into the construction industry.”