STEP students examining the vacuum bag layup of the carbon fiber composite sandwich panel that they assembled.
STEP students examining the vacuum bag layup of the carbon fiber composite sandwich panel that they assembled.

When students new to the Wilson College of Textiles are asked what kind of products are made with textiles, their immediate answers typically include “clothes,” “protective gear,” or “medical products.” The idea of making a snowboard, a ski boat, or even an airplane almost never crosses their minds. Dr. Philip Bradford, an assistant professor in TECS and an engineering project group leader for STEP, is on a mission to change that. He has spent the last two summers developing a STEP curriculum that introduces STEP students to fiber reinforced composite materials. “After the five day program, students leave with not only an appreciation of all the consumer goods made from fiber reinforced composite materials but also an understanding of a few of the industrial processes used to produce them,” explained Bradford . “I designed this program so that students work with a few different fabrication methods and get to take samples of the composites they made home with them.” A total of 19 students over two weeks participated in the composites sessions.

A fiber reinforced composite is a material made up of two main components, high performance fibers and a resin matrix. The fibers give the composite its strength. However, textile fabrics are typically very flexible. To make a ridged composite structure, a resin matrix is added to the fibers or fabrics. The resin bonds all of the fibers together and after it is cured to a solid, gives the composite its shape. Students in the program were instructed through four fabrication methods that increased in complexity each day.

The first day consisted of a method called Wet-Layup. This is the most simple of the fabrication methods where liquid resin was brushed onto fiberglass fabrics, molded and then allowed to cure over night. The second day students used Roll Wrapping to create carbon fiber tubes. This is the same process used commercially to make millions of golf club shafts, hockey sticks, and fishing rods every year. The Vacuum Assisted Resin Transfer Molding (VARTM) process was used on the third day to make a fiberglass composite panel. VARTM is used commercially to make thousands of boat hulls and wind turbine blades. Finally, on the fourth day carbon fiber composite sandwich panels were produced by Vacuum Bagging resin impregnated carbon fiber fabrics, the same process used to produce the highest performance composites for the aerospace industry.

Photos from the composite fabrication methods used throughout the week including: (top left) wetting of fiberglass fabric with epoxy resin for wet-Layup, (top right) wrapping shrink tape on their roll wrapped carbon fiber tube, (bottom left) tracking the flow of liquid resin through their fiberglass fabrics during VARTM and (bottom right) showing off the finished carbon fiber composite sandwich panel made using vacuum bagging.
Photos from the composite fabrication methods used throughout the week including: (top left) wetting of fiberglass fabric with epoxy resin for wet-Layup, (top right) wrapping shrink tape on their roll wrapped carbon fiber tube, (bottom left) tracking the flow of liquid resin through their fiberglass fabrics during VARTM and (bottom right) showing off the finished carbon fiber composite sandwich panel made using vacuum bagging.

Students were also introduced to mechanical testing of materials. Unlike metals or plastics, whose properties are generally uniform throughout a given part, composites’ properties depend on the directions the fibers are oriented. In addition to composites fabrication, students learned about the concepts of stress, strain and stiffness, and how they can change in composite parts due to the fiber architecture. The composite panel that they made using VARTM was cut into strips and tested in tension until fracture. Based on the dimensions of the test strips, the students calculated the strength and strain to failure for the composites.

STEP students watch as their fiberglass composite test strip is tested in tension to failure.
STEP students watch as their fiberglass composite test strip is tested in tension to failure.

The field of composites is a rapidly growing industry.  Under Dr. Bradford’s guidance, the STEP students not only got to experience working with fiber reinforced composite materials in hands-on labs, they also learned just how important textile engineers are in supporting this industry through applying their knowledge of fiber production, textile processing, quality improvement, and mechanics of materials.