Abstract: An improved security door is provided that is a composite of multiple layers. The layers include a first hard layer, a second hard layer, a reinforcing layer disposed between and connecting the first and second hard layers, and a carbonizing layer provided adjacent the reinforcing layer. Other layers, either singularly or in combination, can be included to make the security door further resistant to penetration by various tools. The other layers can include a clogging layer, a mobile layer, a resilient layer, and further reinforcement layers.