Materials for Extreme Environments

Modern cars use lightweight plastics to cushion travelers in high-speed crashes. Police use Kevlar vests to stop speeding bullets.

But the science behind those safety measures isn’t much use to researchers exploring which materials can best mitigate the damage from hypervelocity blasts.

The scorching heat caused by speeds exceeding Mach 5 radically alters how different materials tolerate collision.

“It’s one of the grand challenges,” said Dr. Thomas Lacy, professor in the J. Mike Walker ’66 Department of Mechanical Engineering at Texas A&M University. “The nature of material response is fundamentally different.”

Lacy is on a Texas A&M team that is tackling the problem along with a team of experts in engineering, polymer chemistry, materials science, mathematics and computational mechanics.

This challenge is a key research area for the university through its partnership with Army Futures Command (AFC). Its aim is to mitigate damage from extreme speed blasts and shock waves.

The research might lead to better-built vehicles and safer gear, such as helmets. It could help with construction of protective buildings and low-cost, portable structures that would be flown into endangered areas or be made from what’s readily available nearby.

The research also could improve the materials used to make hypersonic weapons, which have to tolerate weather and possibly other obstacles as they race toward targets.

“It’s really about the material that will withstand hypersonic flight,” said Gen. Mike Murray, AFC commanding general. “That’s the important part.”

Texas A&M will employ an agile methodology in computer modeling, experimentation, adjustment and repetition. The academic team will work closely with Army researchers and other experts in the field.

Much of the experimenting will occur at the Hypervelocity Impact Laboratory, established by Lacy in fall 2019 at the RELLIS Campus.

The lab features a two-stage light-gas gun (two stages of acceleration are needed to reach hypervelocity). The 45-foot gun accelerates 4- to 10-millimeter diameter spherical projectiles up to 8 kilometers per second, the equivalent of Mach 24 or 18,000 mph.

The gun will impact projectiles through a variety of target materials at various speeds and measure the resulting eruption of shrapnel and debris. It uses high-tech diagnostics, including laser intervelometers, high-speed imaging, and in future flash X-ray, ultra-high rate laser diagnostics system to characterize fracture of both projectile and target, study debris cloud expansion and perform three-dimensional fragmentation tracking.

Hypervelocity impact experiments will focus initially on thermoplastic polymer materials, which are plastics that soften when heated, as well as lightweight metals and geomaterials such as concrete. The team also will test layered combinations of various metals, ceramics, polymers and composites.

The entire field of study began out of NASA’s concerns for satellites and other spacecraft being smacked by out-of-this-world debris.

When the Earth’s gravity gets hold of even small pieces of dust in space, the pieces can accelerate to 10 to 70 kilometers per second.

“It’s absolutely devastating,” Lacy said.