Strength enhancement of aluminium foams and honeycombs by entrapped air under dynamic loadings

• Compressive tests were conducted on aluminium foams at intermediate strain rates from 1 to 200 s−1.
• The strain rate effect on aluminium foams and honeycombs were reviewed and compared with data from various sources.
• The strength enhancement of aluminium foams and honeycombs were extensively studied and analysed.
• Possible reasons of the strength enhancement of aluminium foams and honeycombs under dynamic loadings were discussed.

The strength enhancement of cellular metals including aluminium foams and honeycombs under dynamic compression is experimentally studied in the present paper, with a focus on the intermediate strain rate from 1 to 200 s−1. Previously data in this range are very limited due to the difficulty in the experimental techniques. The plateau stress in relation to the strain rate of these materials is discussed based on experimental results and compared with data from literature. It has been found that the studied cellular metals are sensitive to the strain rate in plateau stress but not in densification strain. The causes of the strength enhancement are then discussed with a focus on the contribution of the entrapped air during compression. The results show that the pressure change of the entrapped air during dynamic compression is a direct source of strain hardening for aluminium honeycombs whereas it has less influence on the strain hardening of aluminium foams.