The strength of the 3mm aluminum plate depends on the specific aluminum alloy material and its manufacturing process. Different aluminum alloy materials and different manufacturing processes will have different effects on the strength of aluminum plates.

Generally speaking, aluminum is a lightweight metal, but its strength and hardness can be improved by adding alloying elements and heat treatment. For example, aluminum alloy 7075-T6 is a common high-strength aluminum alloy, and its tensile strength can reach 570 MPa, while the tensile strength of pure aluminum is only about 60 MPa.

In addition, the strength of the aluminum plate is also affected by its surface treatment and use environment. For example, if an aluminum sheet is exposed to moisture or a corrosive environment, its strength may decrease.

Therefore, answering this question requires more specific information, such as the type of aluminum alloy and the specific application environment.