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From its inception, (Santa Cruz, Calif., U.S.) has established itself as one of the front-runners in the advanced air mobility (AAM) market and shows no signs of slowing down. In January 2025, Joby announced it had successfully completed static load testing of the tail structure for its electric vertical takeoff and landing (eVTOL) aircraft and had conducted its first Federal Aviation Administration (FAA) testing under Type Inspection Authorization (TIA), a certification process for an aircraft to begin commercial passenger operations. Joby claims that it is the first eVTOL manufacturer to complete three of five stages of TIA. In March 2025, Joby also announced a partnership with U.K. airline Virgin Atlantic to launch its air taxi service in the U.K.

Joby makes extensive use of composites for its eVTOL aicraft. As it prepares for commercial operations, Joby has explored how to scale its manufacturing. In collaboration with materials supplier Toray Advanced Composites (Morgan Hill, Calif., U.S.), A&P Technology (Cincinnati, Ohio, U.S.) and the (NIAR, Wichita, Kan., U.S.), Joby recently conducted a time study seeking to optimize aircraft part design for high production rates, while meeting cost and sustainability targets. The project involved production of a partial wing spar and studying the manufacturing time and cost differences between two material solutions: A&P’s TX-45 continuous +/-45° braided reinforcement and Toray’s TC380/T800HB 6K traditional 0°/90° woven fabric prepreg.

Initial material iterations and testing

Joby’s current layup method involves cutting Toray TC380 0°/90° 2×2 twill woven prepreg on the bias to achieve plies with 45° orientation. Joby and Toray are working to qualify this material (NCAMP Material Specification NMS 380). In the meantime, Joby saw an opportunity for potential material savings by replacing the woven reinforcement with a braided reinforcement from A&P Technology. According to Chantel Camardese, product manager, thermosets for Toray, the alternate approach uses the same fiber and weave pattern, but is produced on a 45° bias, which aids in drapability and minimizes the need for splicing.

Joby had an interest in A&P Technology’s braided material from early on. According to Joby’s composites rapid development lead Rory Giffen, his team first began working with +/- 45° braided 2×2 twill on the company’s prototype aircraft. The team was looking for continuous +/-45° plies that would simplify ply cutting as well as reduce the overall ply count. They initially experimented with A&P’s Bimax material — which included stabilizing yarns called axials. However, the axials restricted the material’s drapability and ultimately caused Joby to rule Bimax out due to the complex shape of its aircraft.

A&P Technology took this feedback and, after continued iteration, developed TX-45, a pure 45° fabric without axials and in 2023 approached Giffen’s team to run initial trials. While both Bimax and TX-45 enable more efficient processing, TX-45 is more drapable over long, high aspect ratio parts. The TX-45 material was tested using the fuselage skin lamination mold from Joby’s prototype aircraft — the same conditions that raised Giffen’s initial concerns over drapability. After a successful trial, subsequent meetings were scheduled to evaluate TX-45 for adoption in Joby’s production aircraft.

“Right away we were really interested in the TX-45,” says Aurelien Stamper, composites and airframe manufacturing engineering lead, Joby Aviation. “Unfortunately, at the time, we didn’t have the bandwidth to do the trial in-house.” This led Joby and A&P to approach NIAR about performing trials at its facilities in Wichita, Kansas. From there, the layup study was developed.

The scope of the project was to compare prepreg reinforced with traditional woven 0°/90° 2×2 twill to prepreg reinforced with A&P Technology’s TX-45 braided +/-45° 2×2 twill. The study could prove a single batch equivalency between the two approaches and enable Joby to include TC380/T800HB 6K 2×2 twill TX-45 into its qualified products list (QPL), a list of products that have been tested and proven to meet specific quality and performance standards.

Why braid?

Braided reinforcements offer an advantage over a traditional woven prepreg layup by offering long, continuous lengths of off-axis orientation. A bias +/-45° architecture is optimal for various torsion dominated parts, particularly those with high aspect ratios including aerospace parts such as wings, spars and stringers. Additionally, +/-45° plies comprise 50% of a quasi-isotropic layup of woven material (0°, +45°, -45°, 90°). Based on this, A&P Technology set out to prove that TX-45 can provide a more efficient and higher performing material for the +/-45° plies because there would be no splices or waste associated with ply rotation and kitting multiple short pieces.

“There is a lot of waste material when you’re trying to make 0°/90°s and 45°s in the same nested cutting operation,” says Stamper. “To reduce this, we were looking at nesting the 0°/90° and 45° plies separately, even though it would be less efficient. But with the TX-45 material, we saw a huge potential for scrap savings while still being able to nest the plies together.”

Stamper says that Joby wanted to select a part that promised the most benefit during both ply cutting and layup. It also needed a part that was large and and complex enough to provide an accurate representation of the time savings and material savings possible.

“We wanted to make sure we picked a part that was long enough to see the benefit from going beyond the current control width and be able to cut it lengthwise on the table,” says Stamper.

Joby decided on a 40-foot-long section wing spar — roughly a third of the full-size spar. Joby also designed and fabricated the tooling, which it shipped to NIAR along with the TX-45 material provided by A&P. “We looked at many different parts,” says Stamper. “The spar section has a tapered U-channel, which is a bit complex.”

 

Hand layup comparison

One of the goals of the TX-45 time study was to compare the efficiency of ply cutting and kitting, as well as the waste material generated. Engineers were provided with 2D cut files of Joby’s wing section and asked to extract prepreg plies from the TX-45 braided material and Toray TC380 2×2 twill woven 0°/90° prepreg for the layup exercise.

Joby’s AFP senior manufacturing engineer Robin Johnston, the engineer responsible for developing the required cut files and instructions that were used for this trial, supported the trial in person at NIAR. Eight plies, each 12 feet in length, were extracted from the TX-45 material. The TC380 woven material stack of the same sequence of eight plies was made, with each layer consisting of four to five splices in each ply. Material cutting, kitting and hand layup times were recorded to compare efficiency between the two material types during fabrication of the demonstration part.

For consistency purposes, four trained staff personnel were involved in both approaches and the process was monitored to capture the layup time of each ply, robustness of the process and final part quality. The contoured geometry of the part dictated that each ply had to begin from the center of the tool and drape down to the inner and outer radii.

The technicians reported that the initial ply that directly contacts the mold was challenging to lay down on both trials, due to the low tackiness of the mold surface. Application of heat was helpful in securing this first ply.

During the study, braided material showed more flexibility (drapability and conformability) when stretching, compared to the woven material, and generated significantly fewer wrinkles which can contribute to part defects. In addition, the study revealed that it was more challenging to even out wrinkles with the woven twill material and required extra time spent on carefully laying up each section to ensure an effective overlap. The quality and evenness of the final part was much higher on the TX-45 braided wing section.

Splicing requirements for the woven material also presented a challenge. When laying up the 12-foot section with traditional prepreg, each spliced piece had to be carefully guided to match the splice requirements and maintain centerline to even drape lengths on either side.

With the TX-45 material, the splicing requirement was eliminated. Because of this, the ply cutting task was simpler and the expertise required to operate the Gerber (Tolland, Conn., U.S.) cutters was reduced. Simpler ply extraction and kitting significantly reduced the chance of errors during cutting, which also translates into reduced waste during manufacturing.

In fact, minimizing waste was a large part of the motivation behind Joby’s time study. It revealed that the amount of waste collected during the woven twill material cutting was significantly higher than the TX-45 material, largely due to the splicing requirement for the woven material. Although the splices were nested to minimize waste, there was still an uneven number of splice sections with angled shapes that contributed toward scrap sections.

Meanwhile, A&P’s TX-45 material showed significantly lower waste collection. NIAR engineers were able to carefully nest the plies during cutting to gain maximum advantage of the roll and ended up with approximately 25% waste when extracting plies. By contrast, cutting and kitting traditional 0°/90° woven fabric prepreg can yield up to 40% waste. 

Overall, the team noticed a significant reduction in labor to complete the part laid up with TX-45 braided material, compared to the part laid up with the traditional prepreg. In addition, Joby reported that the amount of skill required to complete the fabrication task was lower with TX-45, suggesting simplified layup for production efforts.

 

The quest for simplicity and efficiency

Ultimately, the time study conducted by the partners suggested an approximate 40% reduction in waste and labor through the use of TX-45. Hand layup of the braided TX-45 was simplified, required less technician effort in less time, and produced a better part. The final layup comprised eight uninterrupted plies of TX-45, while the traditional 0°/90° prepreg required 32 splices to achieve the same length and thickness.

Mechanical testing performed by Toray in tandem showed a strong level of equivalency between prepreg produced with the TX-45 braided fabric and prepreg using more traditional 0°/90° twill weave fabric.

“We were really impressed with the quality of the TX-45 braided fabric,” says Russell Kirkman, materials science engineer compositesfor Toray. “It was really easy to prepreg, and the quality of our prepreg came out really good. The initial mechanical testing we did to screen the material for equivalency to the traditional woven twill material was closely in line. So we were really happy with the results. Ultimately, the goal is to have this be a form, fit and function alternative to the standard twill, and everything that we’ve done in the prescreening is pointing towards that being a possibility.”

According to Joby advanced development staff engineer, John Gerigius, there are many advantages to further exploring use of the TX-45 braided material, including reduction in cycle times, reduced weight in parts and a reduction in the number of splices needed, which translates to a reduced number of inspection points — all leading to increases in production efficiency. “This truly should be an industry standard,” he says.

“There were a lot of benefits all around,” Stamper adds, “If we look at the entire global urban mobility industry, it’s only possible if we reduce the overall cost of the aircraft. Being able to bring part cost down by X factor because we’re wasting less material and doing it by using a material like TX-45 that is simple to use — these are huge gains that don’t require a lot of difficulty to get there.”