What is the rear bumper foam called?

[MacQuinn]

The material inside the front bumper is not foam but a composite polyethylene material, also known as a foam buffer layer or low-speed buffer layer. The function of the low-speed buffer layer: As the name suggests, the low-speed buffer layer is a component that provides cushioning during low-speed collisions. This part can reduce the damage sustained by the vehicle in low-speed collisions. In some minor collisions, the low-speed buffer layer may even completely offset the damage to the vehicle. Materials of the low-speed buffer layer: The materials commonly used for low-speed buffer layers are generally polyethylene foam buffer layers, as well as non-metallic resin or engineering plastic buffer layers. Subaru and Honda mostly use metallic low-speed buffer layers.