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I've watched an experiment where they compress a book with a hydraulic press, and the book appears to stay relatively intact under that pressure. It is mentioned that the hydraulic press has a 100-ton pressing capacity. You can watch it from minute 4 here:
https://www.youtube.com/watch?v=AmFe7ECTGQI&t=240s

I've also read somewhere that stacking books under a bed is a potential life-saving precaution if the building were to collapse in an earthquake; as books can withstand immense pressure and can create a pocket of space beside the bed where you can lie down. I've even found a photo depicting it:

enter image description here

A book doesn't deform or break like other solid materials. Of course, there can be tough metals that can stay intact under pressure/loading but a piece of paper is something flimsy. Why are books tough under loading even though they're composed of fragile components? How can we explain the physics behind this phenomenon?

I've also thought that it might be related to chemistry and the structural components of paper like cellulose; but it is mainly the stack of paper that makes a book sturdy.

Another factor that came to my mind is tensile strength but I'm not sure how to explain it within this context. It could be that the tensile strength increases when pieces of paper or books stack up.

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  • $\begingroup$ A single piece of paper is quite strong in compression. Not so good in shear. $\endgroup$
    – Jon Custer
    Commented Oct 10, 2023 at 14:00
  • $\begingroup$ Are you asking why a thin sheet of paper can bend easily, but not be compressed? Or why things are incompressible in general? For example, paper is made from wood, and wood is not very compressible. A rubber eraser is not very compressible, but a kitchen sponge is. A block of steel is not compressible, but a steel spring is. $\endgroup$
    – mmesser314
    Commented Oct 10, 2023 at 15:32
  • $\begingroup$ It's not clear what you're asking about: Why don't solids rearrange and deform easily? What's the origin of stiffness? Why does cellulose form a solid? Why don't books buckle like a single sheet of paper? These are substantially different aspects. Please clarify. $\endgroup$ Commented Oct 10, 2023 at 17:57
  • $\begingroup$ It is a detailed question with visual materials. I'm not sure what is not that clear about it. I'm not a physics expert and asking in layman terms. A book doesn't break or deform like other solid materials. We know that some metals can be very sturdy also. A sheet of paper is not like a tough metal. It is something very fragile. But a stack of paper is very sturdy. I know that a hydraulic press won't do anything to a single sheet of paper but I gave the earthquake example where the pressure under rubble can be a bit more "complex". $\endgroup$
    – ermanen
    Commented Oct 10, 2023 at 18:54
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    $\begingroup$ Why was this closed as needs details or clarity? I think it's clear what you're asking. I don't have reopen votes privilege but I do have upvotes privilege so take that. $\endgroup$
    – CPlus
    Commented Oct 10, 2023 at 20:56

1 Answer 1

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A structure exhibits strength only by avoiding all possible easy failure modes.

A book loaded perpendicular to its pages doesn't buckle because lateral deformation would need to store a large amount of strain energy. (In contrast, a single page loaded lengthwise buckles easily because a large lateral deflection can arise with just a slight bending moment and slight stored strain energy. Even a book loaded parallel to the pages exhibits easy buckling because the pages can slide past each other as they laterally deflect. A book can shear easily as well, also because of this easy slippage.)

A book doesn't squash under uniaxial compression like a ductile metal because its molecular structure doesn't allow easy dislocation movement along slip systems in the manner of a polycrystal. In other words, the cellulose molecule isn't really susceptible to the atom-by-atom defect movement that occurs in an ordered lattice. Tearing pages is largely a matter of pulling the individual well-bonded molecules away from each other.

A book can resist crack propagation better than a single brittle block of wood because the crack comes to an end at the page surface and doesn't start up again easily at the next page. In this way, the pages act like laminations that provide toughness. (But books can be torn lengthwise because a crack runs through the length of each page.)

A book doesn't shatter because it's already mostly surface, when considering the individual pages. (Brittle failure is Nature's way of responding to stored strain energy by choosing as an alternative the energetic price of producing many new surfaces.)

Broadly, materials are strong and tough if most deformation or failure modes would consume energy, rather than release energy. Nature prefers lower-energy states.

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  • $\begingroup$ Thank you for the detailed answer. I'm guessing that cellulose has high tensile strength also due to its molecular structure. $\endgroup$
    – ermanen
    Commented Oct 10, 2023 at 20:28

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