Material And Structure Affect Performance - 3D Printing Technology Application Of Winter Olympic Snowmobile Helmet

Material and structure affect performance - 3D printing technology application of winter Olympic snowmobile helmet

Snowmobiles are one of the fastest and most entertaining events in the Winter Olympics. The outcome is often within milliseconds, so the hardware requirements are very strict. The snowmobile helmet research and development team led by Li Nan, an associate professor at the School of Education (Normal College) of Dongguan University of Technology, participated in the research and development of the snowmobile helmet, which has been used in the training of the national team's Winter Olympics. The team uses 3D reverse modeling and lattice structure 3D printing technology, and collects athletes' data to customize one-to-one snowmobile helmets to meet the actual needs of each athlete. This carefully "intelligent" helmet has the characteristics of personalization, weight reduction, safety and so on. In this issue, the 3D printing technology reference introduces the application of 3D printing technology in the material and structure of this snowmobile helmet.

Choice of materials and structures

According to relevant requirements, the helmet requires all accessories and materials to be China's own.

In the use of materials, the outer layer of this self-developed snowmobile helmet is made of China Aerospace T800 carbon fiber material with high strength and excellent crash resistance. T800 carbon fiber is a new type of high-strength, high-modulus fiber with a carbon content of more than 95%. Because the material is carbonized and graphitized, it has the advantages of low density and high strength. According to relevant information, the density of carbon fiber material is lower than that of aluminum, but its strength is greater than that of steel.

The inner material buffer layer of the helmet adopts a 3D printing lattice structure. The microstructure of the material plays a huge role in its ability to absorb shock. The 3D printing technology reference has learned that the research team has gone through tens of thousands of calculations from the selection of the lattice to the matching of the helmet shell and material properties, and finally determined the optimal one. Lattice structure and materials. Using 3D printing (SLS technology) and TPU powder materials, the lattice structure of the snowmobile helmet buffer layer is designed and developed, which is better than the traditional EPS foam material, and its impact resistance is improved by about 40%, which can resist the helmet when it encounters a collision. Various impact forces, better protection of the athlete's head.

According to the 3D printing technology reference, the helmet made of carbon fiber and TPU lattice structure weighs only about 1.1 kg, which is 500 grams less than the helmet used by the national team before, effectively reducing the weight for athletes. At present, this snowmobile helmet has passed GB and ECE certification, meeting the requirements of the FIS competition helmet, and has been delivered to the national snow team.



3D printing lattice buffer structures using TPU




The lattice structure generally refers to a space truss composed of rods, plates and other micro-elements that are repeatedly arranged according to certain rules. It has the characteristics of low bulk density, large specific surface area, and high specific mechanical properties. The sandwich structure using it as the core material produces huge plastic deformation due to the dynamic instability of the structure under impact load and converts it into heat energy, which can absorb most of the impact energy, so it has excellent buffer energy absorption and impact resistance. , so as to play a protective function.



3D printing has a natural advantage in fabricating lattice structures that can achieve virtually any void accuracy, void fraction, void shape, void size, pore distribution, and interconnectivity. Based on this, the 3D printed lattice structure can make protective sports equipment, which brings new impetus to the transformation and upgrading of helmets, armors and other protective equipment.
Furthermore, the material of manufacture determines the properties and applications of the lattice. TPU has excellent bearing capacity, impact resistance and shock absorption performance, and maintains good physical properties such as elasticity and flexibility even at -35 °C. It is widely used in medical and health, electronic appliances, industry, sports and other fields. At the same time, TPU is also the main elastomer material suitable for 3D printing.

Based on the above factors, the snowmobile helmet team chose TPU as the lattice structure material.

Lattice structure greatly affects buffer performance

In the design of the lattice structure, the size and density of the cell structure and the direction of the cell structure will affect the printability and performance of the lattice structure.

The size and density of a cell structure refer to the size of a single cell and the number of cells in a space. The size of the cell itself is determined by its nodes and the beam width and length connecting the nodes. Larger cells are easier to print and are stronger; smaller cells are relatively more uniform, but are limited by the size of the printing process feature. Usually, the lattice structure does not need support by default. In this regard, it is necessary to pay attention to the design limits in the design process, such as the width of the beam, the inclination angle of the beam, etc.; on the other hand, it is also necessary to pay attention to the placement angle and choose the most ideal The parts are self-supporting in the orientation, reducing processing costs as much as possible and reducing post-processing work. For SLS technology, however, powder materials typically act as a support for the part, thereby reducing the effect of cell structure orientation on printing.

As the Winter Olympics project is still in progress, the performance data of snowmobile helmets, 3D printing technology reference is currently not available. However, some foreign researchers have previously tested the buffering effect of various types of lattice structures on the impact of PA11 printed by HP MJF process and TPU materials printed by laser sintering process. The dynamic impact test uses a 5kg circular metal object dropped onto the test object from a height of 1m, and the test equipment can measure the total impact force absorbed by the sample. From the test process, it can be found that the protection effects of different structures on the impact of the lattice are very different, so researchers can choose the best structure. Funded by the European Union's H2020 Framework Program, the test project includes the study of several techniques for generating lattice structures and the testing of these structures for personal protection in sports such as rock climbing, cycling, skating, etc. helmet.

In order to implement the requirements of "preparing for the Beijing Winter Olympics and Winter Paralympics" and accelerate the "Science and Technology Winter Olympics (2022) Action Plan", in 2019, the Ministry of Science and Technology released the national key research and development plan "Science and Technology Winter Olympics" key special project 2020 Annual project implementation plan. The Science and Technology Olympics will make full use of modern information technology and scientific and technological means, and under the principle of "faster, more convenient, more accurate and safer", so that sports competitions and auxiliary activities can be carried out smoothly.

Compared to traditional foam helmets, 3D printing's leading manufacturing process has inherent custom adaptability and has an independent safety test score that outperforms traditional foam helmets. Assembling the individual components of the helmet, including the printed internal structure and outer shell, the helmet can be printed on demand for improved protection and wearing comfort on the field.

The "Science and Technology Winter Olympics" is a highlight of the Beijing Winter Olympics. Under the guidance of the concept of the "Science and Technology Olympics", countless scientific and technological workers have started the "Olympic Science and Technology Long-distance Run". A stage for self-reliance and self-reliance of horizontal technology. As a new technology that has developed rapidly in recent years, 3D printing has also played a major role in the preparations for the Winter Olympics.