I'm doing a project and wondering if i can use young's module to calculate the elasticity of a material.young's module can only be used for isotropic materials which means the same in all directions, but i'm not sure if plastic is....thanks!
Aircraft-grade aluminum (such as 7075 T651) has substantially smaller tensile strength and elastic modulus than carbon fiber composite (but only along the fiber direction).
You can still use Young's modulus in anisotropic materials, but you will need to know its value along the specific direction you apply the force. Anyway, most usual plastics are isotropic, because they are made by pouring the melted plastic into shapes and letting it solidify. Most plastics don't have a distinct fiber-like structure (like wood does). Even if they are made of strands of molecules (polymers), the anisotropic quality is usually confined to microscopic dimensions, while macroscopically plastics behave in an isotropic way. In tables with Young's modulus values you will also find plastics, which means that they have a sufficiently small anisotropy so that a single Young's modulus value be listed. Everyday use plastics, such as polyethylene, polystyrene, acrylic, etc., don't show any perceivable anisotropy when we use them, unlike wood for instance (that's why it is common to see ply-wood, made of cross-grained layers, but not ply-plastic). Sure enough, you will have anisotropy problems in materials like carbon fiber-reinforced plastics.
