Abstract：A one-dimensional collision model for a large-mass structure protected by high porosity, close-celled aluminum foam subjected to low velocity impact is established and validated with drop hammer tests. Based on the proposed model, the concept of critical impact velocity is introduced, which is dependent upon the mass ratio of the collision system as well as foam porosity. Both the minimum acceleration and critical acceleration of the protected structure are obtained under different impact conditions. It is demonstrated that closed-celled aluminum foams are suitable for protecting large-mass structures subjected to low velocity impact. When the initial impact velocity is lower than the critical one, the stress imposed by the foam on the structure will not exceed the plateau stress of the foam, with the corresponding acceleration of the structure significantly reduced if the foam porosity is relatively high. On the other hand, when the initial velocity exceeds the critical one, due to foam densification, the imposed stress increases sharply (about 5~15 times of foam plateau stress): correspondingly, the acceleration of the structure increases rapidly (even up to 1000g). The influence of impact mass ratio, porosity and geometrical dimensions of foam protection on the critical velocity and acceleration is systematically explored.
2011, Vol. 32 
