system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what's the difference between fiberglass, kevlar, and carbon fiber and what makes them so strong?
gpt
they all have the same basic idea, which is bonding lots of fibres together with some form of plastic to create a material which is much stronger than the individual components. Fibreglass is one of many different types of GRP (glass reinforced plastic). Take a fibreglass canoe. If it was just the plastic 'matrix' material, it would be quite weak and would break easily, but is great for moulding and will take impacts much better than glass, which tends to shatter. By  incorporating glass fibres, the material is made much stronger, but because the plastic is holding all the fibres together, the mixture doesn't shatter as easily as glass. 

It works with pretty much any fibre and plastic-like material. You even see the basic principle in steel reinforced concrete, where steel bars are incorporated into concrete to enhance its strength.