Fiber medicine

A new design approach for manufacturing carbon fibers with optimized orientation and thickness reduces the weight of fiber-reinforced plastics

Carbon is vital for the existence of all living organisms, as it forms the basis of all organic molecules which, in turn, form the basis of all living things. While that alone is impressive enough, it has recently found surprisingly new applications in disciplines such as aerospace and civil engineering with the development of carbon fibers which are stronger, stiffer and lighter than steel. As a result, carbon fibers have taken over from steel in high-performance products like airplanes, racing cars, and sports equipment.

Carbon fibers are usually combined with other materials to form a composite. One such composite material is carbon fiber reinforced plastic (CFRP), which is well known for its tensile strength, stiffness and high strength-to-weight ratio. Due to its high demand, researchers have conducted several studies to improve the strength of CFRPs, and most of them have focused on a particular technique called “fiber direction design”, which optimizes fiber orientation to improve resistance.

However, the fiber-driven design approach is not without its drawbacks. “The fiber-oriented design only optimizes the orientation and keeps the fiber thickness fixed, preventing full utilization of the mechanical properties of CFRP. A weight reduction approach, which also optimizes fiber thickness, has rarely been considered,” says Dr. Ryosuke Matsuzaki of Tokyo University of Science (TUS), Japan, whose research focuses on on composite materials.

In this context, Dr. Matsuzaki – together with his TUS colleagues, Yuto Mori and Naoya Kumekawa – proposed a novel design method to simultaneously optimize fiber orientation and thickness as a function of location in the composite structure, which allowed them to reduce the weight of the CFRP compared to that of a constant-thickness linear lamination model without compromising its strength. Their findings can be read in a new study published in Composite works.

Their method included three stages: the preparatory, iterative and modification processes. In the preparatory process, an initial analysis was carried out using the finite element method (FEM) to determine the number of layers, allowing a qualitative evaluation of the weight by a linear stratification model and a fiber driven design with a thickness variation model. The iterative process was used to determine fiber orientation by principal stress direction and iteratively calculate thickness using “maximum stress theory”. Finally, the modification process was used to make modifications with manufacturability in mind by first creating a reference “base fiber bundle” in a region needing strength improvement, then determining the orientation and the final thicknesses by arranging the fiber bundles so that they extend on both sides of the reference batch.

The simultaneous optimization method led to a weight reduction of more than 5% while allowing greater load transfer efficiency than obtained with fiber orientation alone.

The researchers are excited about these results and look forward to future implementation of their method to further reduce the weight of conventional CFRP parts. “Our design method goes beyond the conventional wisdom of composite design, making aircraft and automobiles lighter, which can help conserve energy and reduce CO2 emissions,” observes Dr. Matsuzaki.

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Materials provided by Tokyo University of Science. Note: Content may be edited for style and length.