Tech Briefs

Basalt fabrics have ballistic properties for potential use in body armor.

Basalt rock is a black or gray fine-grained rock in the family of igneous rocks, formed by cooling of molten lava. It is commonly found in the Earth’s crust, is abundant throughout the world, and can be easily mined. Basalt rock possesses certain qualities similar to thermoplastics and metals, i.e., it melts when heated to specific temperatures (1100 to 1300 °C), and can be drawn into flexible fibers, a process similar to the manufacture of S-2 and E-glass fibers.

Three weave styles of Basalt Fabric were investigated (left to right): The 8-harness satin weave, a plain weave, and a 2/2 twill weave. Basalt fabrics tend to be brownish in color due to the high iron content.
Along with the two obvious uses as toughening and insulation material, it is claimed that the fibers are naturally resistant to ultraviolet (UV) and high-energy electromagnetic radiation, maintain their properties in cold temperatures, and provide excellent acid resistance. The fibers are produced in a continuous process, similar to that for making glass fibers. The basalt material is initially fed into a heating furnace, followed by gravity feed through a bushing, and finally gathered into a single strand of continuous filament basalt fiber. The material is then quenched with a water-based sizing and packaged for sale.

There are certain things about basalt that make it attractive and economically comparable with production of glass fibers. Part of the process in the production of high-quality glass fibers involves addition of ingredients such as aluminum and other minerals needed to create the desired chemical and physical properties of the final product. Additional steps and ingredients will always increase production cost. Since natural basalt already contains these ingredients, these steps are eliminated from the manufacturing process.

Since basalt fabrics are fairly new for Army applications and currently in limited use, selection of different types and weights of fabric were considered for this study. The main goal is to obtain different products and perform the evaluation assuming that a lighter fabric or style may be better suited for smaller threats.

The raw material was purchased from Martintek U.S.A., Hexcel Corp., BGF Industries, and Sudaglass Fiber Technology. All of these vendors use basalt filaments manufactured and supplied by Kamenny Vek. These fabrics were infused with SC-15 epoxy resin at the Army Research Laboratory (ARL). Composite plates were fabricated at two areal densities, and the average fiber volume was 45%. There were three different weave styles: the 8-harness satin weave, a plain weave, and a 2/2 twill weave.

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