If you have been heavily influenced by 3D printing or are just a fan of the many innovations brought forth today, chances are you have also become far more knowledgeable about materials science than you ever imagined. While in the beginning 3D printing was greatly ruled by thermoplastics such as ABS and PLA, the list of materials today is expansive—with some being wildly alternative from chocolate to hemp—and the choices just continue to grow.
Metamaterials allow researchers to create on an even more elevated level, and continued strides may change the face of how numerous applications are manufactured in the future. Recent work by Beijing researchers, discussed in ‘Deformation mechanism of innovative 3D chiral metamaterials,’ explores the importance of man-made materials that can be microstructured to include properties not available naturally. They also examine deformation mechanisms, to include:
- Uniform spatial rotation deformation
- Tensile-shearing directed
- Tensile-expansion directed
- Deformation mechanisms of 3D chiral metamaterials
- Deformation mechanism competition between varying types
The chiral metamaterials explored by the team of researchers offers strong potential for designing with a variety of strengths and densities, sound metamaterials, electromagnetic metamaterials, optical metamaterials, and more. The research paper goes into detail regarding the expanding qualities of auxetic metamaterials, along with their ‘enhanced’ mechanical properties.
“Auxetic materials can be applied for designing innovative multifunctional structures, such as: body armor, packing material, knee and elbow pads, robust shock absorbing material and sponge mops. According to the geometrical relations of auxetic unit cell, there are mainly three types of auxetic materials: reentrant materials, rigid square rotation materials and chiral structures,” state the researchers.
A chiral structure is one that cannot be separated into two identical halves. A good example is that of a DNA strand. The researchers point out that other natural chiral materials are that of flower petals and stems that climb in a twisted fashion, as well as ‘tendrils and twisted leaves.’
“Because of their lack of mirror symmetry, chiral metamaterials have recently enabled several remarkable phenomena, such as negative refractive index, superchiral light, and use as broadband circular polarizers or detectors,” state the researchers.
With 3D printing, chiral structures can be fabricated with even greater functionality in applications such as electronics. In the scope of this research study, the team focused on chiral- chiral- antichiral, and chiral- antichiral- antichiral metamaterials. Type A and Type B were 3D printed on an SLS 3D printer at BMF Material Technology, Inc. in Guang Dong Province of China.
The nylon was evaluated before compression tests began:
“Totally, 5 uniaxial tensile samples are fabricated, and uniaxial tensile experiments are performed on an Instron®5985 machine at a displacement rate of 1 mm/min. Finally, the average elastic modulus of the 5 as-fabricated tensile samples is:Es = 1021.00 MPa, where the deviation of modulus is: ±0.75 MPa, and the average ultimate strain of the material is εmax = 0.16,” stated the researchers.
The researchers then employed compression tests, noting:
- Loading force
- Displacement images
- Deformation images
Axial strain and compression stress were created as the researchers worked to minimize friction. Beyond that, they continued to simulate deformation and then compare all the results.
“With the progress of micro- and nano- manufacturing techniques, the proposed 3D chiral metamaterials show promising performances for future industrial applications, such as: nano chiral metallic glass with extensive hardening and large ductility, sound absorption and vibration attenuation metamaterials, morphing structures, optical chiral metamaterials, shape memory actuators and biomechanical devices,” concluded the researchers.
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