Is it true that ice cubes mixed with cotton cannot be broken even with a hammer?

Winter is coming, and as the temperature gradually drops, the day when ice forms everywhere is approaching.

Speaking of ice, I believe many of you have had the experience of looking at the beautiful ice surface that has just been frozen and suddenly having the urge to smash it hard.

This is what happens when you misjudge the thickness of the ice (GIF from SOOGIF)

However, there is a kind of ice that "cannot be broken no matter how hard you hit it". The legend about it has been circulating on the Internet for many years. Even the British Navy during World War II had the idea of ​​using similar materials.

Yes, it's this white ice cube.

Behind this material lies the knowledge of structural reinforcement technology which is quite common in materials science.

Today, let us share with you some stories and related knowledge about these "adulterated ice"!

Is it true that ice mixed with cotton cannot be broken?

There is a story circulating on the Internet: Although ordinary ice is hard, it can always be broken with enough force. However, if cotton is added to the water before freezing, the ice will become like reinforced concrete and cannot be broken no matter what.

Is this really the case? Let's analyze what happened here from a scientific perspective!

First, we take ordinary water ice, which is common in daily life, as the research object. Ice is a hard material. When the temperature is low enough, it has a certain structural strength. According to the data of the China Meteorological Administration, the tensile strength of ice is about 1.2~1.5Mpa , and the compressive strength is between 3.5~4.5Mpa . It can be seen that this is a brittle material with stronger compressive strength than tensile strength.

Referring to the common glass in our lives, the characteristic of brittle materials is that they are relatively hard , but when subjected to external stress impact, the local deformation can easily exceed its tensile strength , thus being destroyed.

There is some flexibility, but not much (GIF from SOOGIF)

Now let's look back. Cotton, as a common material, has almost no compression resistance, but it has strong tensile strength. A ball of cotton can be pulled into a long cotton thread without breaking. In this case, can the characteristics of cotton and ice complement each other?

Adding cotton to ice is a type of fiber-reinforced composite material in materials science. When ice with cotton is impacted by external forces, the mesh structure of the cotton can effectively conduct stress along the fibers , thereby reducing the amplitude of local deformation and preventing the ice from breaking.

In addition, when cracks appear in the ice, the cotton fibers can also act as a skeleton to prevent the extension of the cracks , thereby increasing the toughness of the ice. On the contrary, when ice without cotton is hit with the same force, it is more likely to crack and break due to the lack of support from this mesh structure.

However, since most of the netizens did not give a definite ratio of ice to cotton during the test, it is difficult for us to discuss the strength of this material here. Fortunately, there was a crazy plan in history that used a very similar material, from which we can also roughly understand how much the fiber skeleton can improve the performance of the material.

Churchill did it too!

World War II British Ice Carrier Plan!

In the 1930s, the idea of ​​using ice to build ships became popular, and the cold of the North Atlantic also provided realistic conditions for the existence of ice ships. However, as we mentioned above, due to the poor tensile properties of ice, the overall reliability of ships made of ice is at a desperate level.

However, with the advancement of materials science, American scientists Hermann Mark and Walter Hornstein discovered that mixing 14% sawdust with water and freezing it can significantly increase the tensile strength of ice. At the right temperature, its compressive strength can reach 7.584Mpa and its tensile strength can reach 4.826Mpa .

Pikerite's raw materials and a finished product

This material was named Pykrete . Its density is not much different from that of ordinary ice, but it has good machinability, very low thermal conductivity, low cost and a structural strength that is even close to that of concrete at the time.

Due to the good performance of Pyrite, in 1942, when Britain was besieged by Nazi Germany's unrestricted submarine warfare and was at its wits' end, General Mountbatten and the then British Prime Minister Churchill proposed a plan to build a warship with this material. The goal of this plan was to build a super ice aircraft carrier named Habakkuk .

In the design, the Habakkuk had a total length of 610 meters, and some records even said it was 1,200 meters long. It had a total weight of 2.2 million tons , was equipped with 26 engines, and had a maximum speed of 7 knots. It could carry 200 fighters and 100 bombers. Even the modern Nimitz-class aircraft carrier is less than 1/4 of its size, making it a true war behemoth.

The planned aircraft carrier is incredibly huge

In May 1943, engineers used Pykrite to build a 20-meter-long experimental model on Lake Patricia in Canada. With the blessing of various insulation methods, this big, white (maybe not so white) ice block spent the whole summer smoothly.

This gave Churchill great encouragement. At the Anglo-American joint operations conference in August 1943, General Mountbatten vigorously promoted their ice carrier plan.

According to unofficial records, he placed a piece of ice and a pikeret of the same size side by side in the conference room, and without warning, he fired a shot at each of the two pieces of ice. The ordinary ice was shattered as expected, but the pikeret actually deflected the bullet , so everyone could see a pistol bullet flying around in the conference room full of senior Allied officers, and almost injured the US Navy Admiral Ernest King who was present.

A shot-shot piece of Pykret

Fortunately, the battle-hardened generals present were not thrown off by this incident. The leaders of the allied countries were amazed at the excellent performance of this material, so the construction of Habakkuk was officially put on the agenda.

However, in a series of subsequent tests, engineers found that Parkrite could only remain rigid below minus 15 degrees Celsius , but the waste heat emitted by the aircraft carrier's 26 engines during operation was enough to melt the entire ice block. Therefore, only by installing 16 additional ice plants inside the aircraft carrier could the temperature be barely kept stable.

In addition, since the entire aircraft carrier is made of ice, ordinary watertight design is completely ineffective, and the cabin will be very dangerous when facing a torpedo attack. In order to solve this problem, the thickness of Habakkuk's bulkhead reached an astonishing 40 feet, about 12 meters , which can physically withstand the explosion of German torpedoes without damage. This makes the already huge aircraft carrier design even larger, and the larger overall design puts forward new requirements for the internal structure...

Add more water to the noodles, add more noodles to the water, and finally change the basin

In this way, in the process of adding more flour and more water, other technologies have advanced to overcome the problems that Habakkuk originally designed to solve. Finally, in December 1943, the project was rejected by the Joint Chiefs of Staff, and this crazy plan came to an end.

Fiber-reinforced composites

Although the "Habakkuk" aircraft carrier plan was ultimately not realized, through this plan, we can intuitively see the significant improvement of fiber on the performance of composite materials. Just adding a proper amount of sawdust to ice can make it have certain potential for military use. This qualitative leap is amazing.

In fact, composite materials made by combining the strengths of different materials have been widely used in our lives. Composite materials are multiphase materials made by combining two or more materials (such as metals, ceramics or polymer materials ) through a composite process. These materials complement each other in performance and produce a synergistic effect, making the comprehensive performance of composite materials better than that of a single material, thus meeting various needs.

The history of composite materials can be traced back to ancient times. Clay reinforced with rice straw or wheat straw, which has been used since ancient times, and reinforced concrete, which has been used for hundreds of years, are both made of two materials. At almost the same time when Parkrite appeared, glass fiber reinforced plastic (commonly known as FRP ) was already used in the aviation industry.

The first aircraft to use fiber-reinforced plastics, the Fairchild F-46

Among composite materials, fiber-reinforced materials are the most widely used and have the largest usage. They are characterized by low specific gravity, high specific strength and specific modulus . For example, the specific strength and specific modulus of carbon fiber and epoxy resin composite materials are several times greater than those of steel and aluminum alloys. They also have excellent chemical stability, friction reduction, wear resistance, self-lubrication, heat resistance, fatigue resistance, creep resistance, noise reduction, electrical insulation and other properties.

Another characteristic of fiber-reinforced materials is anisotropy , so the fiber arrangement can be designed according to the strength requirements of different parts of the part, which is very attractive for certain highly customized needs.

The fifth-generation fighter jets use a lot of composite materials to improve flight performance. The picture shows the Su-57 produced by the Sukhoi Design Bureau and the J-20 produced by AVIC Chengfei.

At present, fiber-reinforced composite materials are widely used in high-tech fields such as aerospace, automobile, chemical industry, and machinery equipment manufacturing . They are also used as building materials or raw materials for certain sports equipment .

At this point, some of you may ask: "Since composite materials are so powerful, why haven't they completely replaced traditional materials?"

In fact, everything in the world has its two sides. Although composite materials have many amazing advantages, they are not perfect , and they also have some disadvantages that cannot be ignored.

First, the high performance of composite materials is often accompanied by high costs . The cost of matrix materials such as high-performance fibers, resins, and ceramics is not low in itself, and the processing of these materials requires special processes and equipment, which further increases the cost of using composite materials. Therefore, despite the excellent performance of composite materials, in some areas, high costs are still an insurmountable threshold.

Secondly, the interface problem of composite materials is also a major challenge. In composite materials, the interface strength between the fiber and the matrix directly affects the performance of the material . However, in long-term use, the interface of some materials may gradually fail due to fatigue damage, resulting in a decrease in overall performance. In addition, the complex structure of composite materials makes performance prediction more difficult, which puts higher requirements on design and application.

What is even more troubling is that the recycling of composite materials is still a problem. Due to the close bonding of fibers to the matrix, recycling composite materials is more complicated than traditional materials. If not recycled properly, some composite materials may even cause harm to the environment, such as composite materials containing asbestos fibers. These problems make the sustainable development of composite materials face challenges.

Nevertheless, we do not need to be too pessimistic. With the continuous advancement of technology , many shortcomings of composite materials are gradually being solved. For example, the development of new environmentally friendly resins, more efficient recycling technologies, and more accurate performance prediction models are paving the way for the application of composite materials. We have reason to believe that composite materials in the future will be more mature, more environmentally friendly, and shine in more fields.

References

[1]https://en.wikipedia.org/wiki/Pykrete

[2]【“This one is really a heavyweight!” Habakuk, a giant aircraft carrier built of ice! [Fengfan said]】 https://www.bilibili.com/video/BV1dC411p7xj

[3] Anonymous. Britain's "Ice Carrier" Plan during World War II[J]. Science Grand View Garden, 2012, (05): 40-41

[4] Shi Mu. The aborted story of the ice-made aircraft carrier[J]. Big Science (Science Mysteries), 2011, (05): 30-32.

[5] Wu Minghua. “Ice Carrier” Mountbatten’s Maritime Delusion[j]. See the World, 2010, (08): 60-61.

[6] World War II Fantasy: Detailed Explanation and Debunking of Ice Carriers https://weibo.com/ttarticle/p/show?id=2309404231996204304322

[7]https://baike.baidu.com/item/%E5%A4%8D%E5%90%88%E6%9D%90%E6%96%99

[8]https://en.wikipedia.org/wiki/Fibre-reinforced_plastic

[9]https://en.wikipedia.org/wiki/Carbon-fiber_reinforced_polymer

Planning and production

Source: Institute of Physics, Chinese Academy of Sciences (id: cas-iop)

Editor: Wang Mengru

Proofread by Xu Lailinlin