In 2012, CEO of Tesla and SpaceX, Elon Musk, proposed the Hyperloop, a new form of transportation that could be sustainably self-powered and twice as fast as a plane. Here, Benjamin Stafford, materials science specialist at Matmatch, explains the design considerations for engineers developing the next generation of transportation systems and the following materials:
- carbon fiber
Humankind has come a long way since the days of travelling on foot. The 20th century, in particular, saw a significant number of developments and improvements to land and air transportation. Now, talk of walking from London to Edinburgh would seem ridiculous with the various methods of transport available.
Today, automotive and aviation manufacturers are under increasing pressure to reduce harmful emissions and meet global targets to tackle climate change. In addition to creating faster and more efficient transportation modes, like those we’re seeing with the advances in the electrification of both cars and planes, governments have another issue to address.
Our roads, airports and ports are congested. Countries like Mexico, Thailand and Indonesia currently rank as having cities with the highest traffic-related congestion but there are few ideas on how to reduce it. Well, that was the case before Musk’s revelation of the Hyperloop.
What is the Hyperloop?
Hyperloop is an ultra-high-speed transportation ecosystem, made up of a system of tubes that pods can travel through free of air resistance and friction. The Hyperloop works by replicating high altitudes in a low-pressure environment inside the tube system by removing most of the air with vacuum pumps, which drastically reduces the drag forces.
Due to the ultra-low aerodynamic drag, the pods can glide at airline speeds for long distances, providing rapid transit across densely populated regions. In the US for example, a Hyperloop could enable travel from New York to Washington DC in less than 30 minutes. It’s estimated that the Hyperloop’s pods will be able to travel at around 600 miles per hour, carrying up to 16 passengers.
Member of the Delft University of Technology’s Hyperloop team, Mark Geuze, described the Hyperloop as “being able to connect cities, making it more efficient than a plane, but as convenient as a train”. While projects like Virgin Hyperloop One Systems and Hyperloop Transportation Technologies (HTT) are working to make Musk’s concept a reality, there are still some elements of design that need refining.
For the Hyperloop to be two to three times faster than existing high-speed rail and magnetic levitation trains, and ten to fifteen times faster than traditional rail, design and mechanical engineers are looking to materials used in the aerospace industry for inspiration.
This is because the Hyperloop needs to be constructed with robust materials that are light and able to withstand extreme conditions, particularly at low pressures, like those used in the aircraft.
Carbon fiber in Hyperloop
While most of the modern aircraft are made from aluminium, composite materials such as carbon fiber are becoming increasingly popular.
Composite materials include some of the most advanced engineering materials today and Matmatch has over 100 composites listed on its site. The addition of high strength fibres to a polymer matrix can greatly improve mechanical properties, such as the tensile strength and temperature resistance.
This year’s Hyperloop competition took place on 21 July in Los Angeles, USA. At this competition, students from all over the world competed for the fastest, best pod system.
The student team of Technical University of Munich (TUM) presented the new Hyperloop pod prototype made from carbon and for the third time in a row took the first place. In 2018, the special capsule from Munich flew through the 1,200 metres test tube at a velocity of 467 km/h, leaving the competition in the dust.
This year was once again all about maximum speed. “The pod has to be especially light, but at the same time extremely stable to withstand loads of the high speeds in the tube,” explains Paloma García Guillen, Structure Team Lead in the TUM team.
All properties that are typical features of carbon fiber. “Thanks to the support from SGL Carbon, we were able to test out different material variants.” Ultimately, the team opted for a pre-impregnated woven carbon fiber material, a so-called prepreg.
Based on the design and material optimizations, the carbon component of the current pod weights around 10% less than the previous model (5.6 kilograms compared to 6.1 kilograms).
In addition, the mounts for the shell are now built completely out of carbon, instead of the previous plastic solution, cutting the weight in half from 1.5 kilograms to just 700 grams.
Vibranium for Hyperloop pods
In the development of its Hyperloop pods, HTT has developed a new type of carbon fibre composite withd embedded sensors that is eight times stronger than aluminium and ten times stronger than steel alternatives and transmits critical information regarding temperature, stability, integrity and more, wirelessly and instantly. It is also much lighter in weight—roughly five times less than steel and 1.5 times less than aluminum—reducing energy output to propel the capsule. The material, named “vibranium” (inspired by Marvel’s fictional metal), has been designed to be a skin type material to protect the Hyperloop pods.
The pods are constructed with two layers of vibranium, one for the exterior and one for the interior of the pod, with an array of sensors sandwiched between the two composite material layers. These sensors can monitor the pod’s stability, temperature and integrity in real-time to maximise passenger safety.
As if selecting the materials for the Hyperloop’s pods wasn’t complex enough, designers will also have to consider the tubes when this new mode of transportation becomes a reality. Luckily, designers can compare materials for complex projects like the Hyperloop by using Matmatch’s online database, allowing them to easily make an informed decision to develop an effective product.
Steel and concrete for the Hyperloop structure and tubes
The tubes for Hyperloop need to be strong, stiff, durable and airtight. Currently, the preliminary design for the tubes is made in steel, however alternative tube design in concrete is also considered (ultra-high-performance steel fibre reinforced concrete (UHPFRC).
The Hyperloop system by HTT consists of large tubes made of steel and concrete. These tubes will primarily be built on pylons, with some ground level and underground segments as needed.
The elevated system results in lower the cost of land acquisition make it impervious to weather conditions, resilient to earthquakes, eliminates the possibility of collision with road traffic, and will provide eco-opportunities.
The Hyperloop design report by MIT Hyperloop Team for the SpaceX Hyperloop
Competition 2015-2017 mentions the use of steel 1018 steel.
However, recently composite materials have been proven to be a great alternative to conventional metal in several industries, most noticeable in aerospace applications and rapidly emerging in civil structures.
Composite materials have various structural advantages compared to steel. For example, composites are relatively lightweight compared to steel. This means that hyperloop tubes can be lighter and still meet the structural requirements.
Furthermore, the composite tubes will have to become thicker than steel tubes. Increased wall thickness has the structural benefit of being less prone to buckling mechanisms. Lastly, due to the lower sensitivity to temperature changes, the composite tubes will also have fewer problems regarding heat expansion.
Aside from the structural advantages, composite tubes also provide interesting production methods. For instance, the continuous filament winding process offers great potential for the production of hyperloop tubes.
With this method, large tube sections can be produced at once, leaving the structure with less connecting elements. Furthermore, this winding process offers the possibility to function as a pop-up factory. This would enable the composite tubes to be produced on-site which will remove the logistical challenge of moving large tubes to their locations.
Lastly, composite tubes have several financial advantages. Even though the price for composites is higher than that from steel, composites have the potential of lowering the cost of investment.
This is mainly due to the lower amount of material that is required. Furthermore, the opportunity to produce the composite tubes on site can allow for cost reduction in the logistics process.
While the Hyperloop certainly offers a faster, safer and more efficient mode of transport, it will be a few years before we will be able to use these underground systems as part of our daily commute. In the meantime, we can expect modern aircraft to become even more advanced, thanks to better materials selection.
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