Can sand castles offer the best protection?

Sand has the potential to resist impact better than steel, according to a team of engineers from Singapore.

Sand has the potential to resist impact better than steel, according to a team of engineers from Singapore.

While sand has been often used in military fortifications, little was known about its energy absorption capabilities so the team from the National University of Singapore (NUS) conducted a number of tests where projectiles of various shapes and masses were fired against a silica sand block. They found that sand can absorb more than 85 per cent of the energy exerted against it.

“Our findings show that sand holds a strong potential as a receiving layer of a composite material subjected to impact,” said Assistant Professor Darren Chian Siau Chen from NUS Civil & Environmental Engineering.

Interestingly, they also found found that resistance offered by the sand block increases with the speed at which projectile travels. Different nose shapes and masses of projectiles were fired at a wide range of velocities. The impact also results in an extreme frictional force that could cause the projectile to break into pieces.

The team believes that the findings of their study may expand the applications of sand, which is presently used extensively in areas such as glass making, building construction and land reclamation.

“These unique characteristics of sand may open up exciting new applications in areas that impact our daily lives, as well as in defence," said Prof Chian.

"For instance, steel, which is one of the key materials used in the construction of armour systems, can be partially replaced with sand as a cost effective, environmentally friendly, and lightweight sacrificial layer, given its superior energy absorption performance. Given the possibility of hostile threats, sand could also be used as a complementary building material to steel to enhance protection of critical infrastructures and household shelters, given its projectile resisting function.”

The team will next conduct larger scale trials to further study the ability of sand to resist impact, as well as starting research into the energy absorption capabilities of similar materials, such as rock rubble.

[Asst Prof Darren Chian Siau Chen (seated) with fellow team members Asst Prof Anand Sarma (left) and Assoc Prof Vincent Tan. Photo: NUS]