A team of researchers from Khalifa University has developed an approach to model the behavior of woven fabrics under stress cycles. Modeling this allows manufacturers of aircraft components to choose the most appropriate materials.
The aerospace industry is continuously searching for materials that are lightweight but strong enough to resist the stresses and strains of flight. Advanced composite materials including 3D orthogonally woven fabrics (fibers woven at right angles) offer many unique features and benefits over other materials, but before they can be used, they need to be tested.
A team of researchers from Khalifa University has developed an approach to model the behavior of fiber-reinforced polymer composite (FRPC) fabrics under stress cycles. Woven fabrics will compress and relax in a particular way that depends on the architecture and properties of the fabric reinforcement used in the manufacturing process. Modeling this allows manufacturers of aircraft components to choose the most appropriate materials.
The team included Siddhesh Kulkarni, Masters Student; Dr. Rehan Umer, Associate Professor; Prof. Wesley Cantwell, Aerospace Engineering; Khalid Alhammadi, Undergraduate Student; and Dr. Kamran Khan, Associate Professor. Their results were published in Composites Part A: Applied Science and Manufacturing.
A composite material is a combination of materials designed to achieve specific structural or performance properties. FRPCs are one such type of composite used in aerospace applications. They are manufactured using liquid composite molding (LCM) processes, where a dry fabric reinforcement is kept between two molds and then compacted to a target thickness while a liquid resin is injected into the fabric.
FRPCs can enhance structural performance in an aircraft while reducing weight. Their high strength, load-bearing capability, high corrosion resistance, and enhanced durability makes FRPCs state-of-the-art materials in aerospace applications.
Fibers in such composites can be woven in either two or three dimensions, with 3D fabrics preferred for critical structural components, such as engine fan blades, as they offer higher stiffness and out-of-plane strength.
“Woven fabrics exhibit a viscoelastic response that depends on the fiber reinforcement,” Dr. Khan said. “This means that the fabric’s stress response will depend not only on the deformation, but also on the rate of deformation during compaction.
Furthermore, when the fabric is held at a constant thickness after compaction, it exhibits relaxation of stresses. Therefore, the rate-dependent viscoelastic compaction response also needs to be considered when modeling the fabric’s behavior under various stresses.”
The compaction behavior of fabric reinforcements demonstrates a unique, non-linear stress-deformation response curve. Using this knowledge, the team experimentally investigated the rate-dependent response of a 3D orthogonal woven fabric under different loads and developed a model to understand how the fabric would respond. Their model could also predict the fabric’s response to stress until the cycles of compaction and relaxation caused microstructural changes, which the team found became extensive after four rounds of testing.
“This work is a continuation of a project that focused on introducing 3D reinforcements in Aerospace composites such as the fan blade of an aircraft engine,” Dr. Khan said. “There are issues related to processing thick 3D preforms to achieve high fiber content and better resin permeability. The modeling work helps to predict mold clamping forces hence identifying strategies to inject resin in an LCM mold.”
14 March 2023