A new design approach for manufacturing carbon fibers with optimized orientation and thickness achieves weight reduction in fiber reinforced plastics. Carbon fibers, due to their superior strength and lightness, are popular in aerospace engineering applications. Carbon fibers are stronger, stiffer, and lighter than steel. Carbon fibers are usually combined with plastics to form carbon fiber reinforced plastic (CFRP), which is well-known for its tensile strength, rigidity, and high strength-to-weight ratio. Owing to its high demand, researchers have carried out several studies to improve the strength of CFRPs, and most of these have focused on a particular technique called "fiber-steered design," which optimizes fiber orientation to enhance strength.
Now, researchers from Tokyo University of Science have adopted a new design method that optimizes both fiber thickness and orientation, achieving weight reduction in reinforced plastic and opening doors to lighter aircrafts and automobiles. "Fiber-steered design only optimizes orientation and keeps the thickness of the fibers fixed, preventing full utilization of the mechanical properties of CFRP. A weight reduction approach, which allows optimization of fiber thickness as well, has been rarely considered," explains Dr. Ryosuke Matsuzaki from Tokyo University of Science (TUS), Japan, whose research is focused on composite materials.
Against this backdrop, Dr. Matsuzaki-along with his colleagues at TUS, Yuto Mori and Naoya Kumekawa-proposed a new design method for optimizing the fiber orientation and thickness simultaneously depending on the 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 Structures.
Their method consisted of three steps: the preparatory, iterative, and modification processes. In the preparatory process, an initial analysis was performed using the finite element method (FEM) to determine the number of layers, enabling a qualitative weight evaluation by a linear lamination model and a fiber-steered design with a thickness variation model. The iterative process was used to determine the fiber orientation by the principal stress direction and iteratively calculate the thickness using "maximum stress theory". Finally, the modification process was used to make modifications accounting for manufacturability by first creating a reference "base fiber bundle" in a region requiring strength improvement and then determining the final orientation and thickness by arranging the fiber bundles such that they spread on both sides of the reference bundle.
The method of simultaneous optimization led to a weight reduction greater than 5% while enabling higher load transfer efficiency than that achieved with fiber orientation alone.
The researchers are excited by these results and look forward to the future implementation of their method for further weight reduction of conventional CFRP parts.
Source : Tokyo University of Science
Title of original paper: Variable thickness design for composite materials using curvilinear fiber paths
Journal: Composite Structures