I News
The high strength and complex geometry of the aircraft luggage compartment B bracket produced by TxV are attributed to the use of hybrid composite molding.
Typically, aerospace companies are willing to pay more for more suitable composite parts because they know that such efforts will pay off. Because of its light weight, it can reduce fuel consumption; because of its durability, it has a longer service life and reduces operating costs. This "full life cycle" perspective opens the door to many terminal application markets for composite materials. However, even with all the above advantages, its cost disadvantage is obvious. It is well known that under current conditions, the production cost of composite parts is much higher than that of metal materials.
However, this situation is quietly changing.
The new composite automated production technology launched by TxV Aero Composites in the United States is tilting the low-cost balance towards composite materials. This technology is called "hybrid composite molding process."
TxV Aero Composites is a joint venture between Tri-Mack Plastics Manufacturing and Victrex. Its hybrid composite molding process has been aimed at commercial-scale mass production since its launch. TxV has now partnered with SFS intec Aircraft Components of Germany (hereinafter referred to as SFS intec) to abandon the previously used aviation aluminum materials and redesign the composite aircraft luggage compartment bracket products, which have the ability to be mass-produced. The successful launch of this product shows the potential of hybrid composite molding process and Victrex's carbon fiber/PAEK unidirectional prepreg tape product named VICTREX AE 250 in many aviation fields. If the production of traditional metal parts is called a "subtractive process", then the production of composite parts can be called an "additive process".
From "subtractive" to "additive"
Machinists often jokingly call themselves "waste making machines" because a lot of debris and waste are generated in the process of processing metal sheets into metal parts. They are either recycled, processed, or immediately put back into production. But no matter which method is used, it cannot change the fact of waste, and it directly increases production costs. It is said that taking the aluminum bracket of the aircraft luggage compartment produced by SFS intec as an example, after a series of machining links, the scrap rate is as high as 60%-70%.
Because of such a high scrap rate, the cost of composite materials is lower than that of aluminum, whether it is a net shape or a near net shape bracket, only from the perspective of raw materials. "Although aluminum is cheaper, the high scrap rate gives composite materials an opportunity to compete from a cost perspective. Especially when the BTF ratio (buy-to-fly ratio) reaches 8:1 (the scrap rate is as high as 87.5%), most of the purchased aluminum is wasted." Jonathan Sourkes, account manager of TxV, said, "In addition, from the perspective of production cycle, composite materials are also very advantageous. It can shorten the production cycle from hours to minutes."
In addition, composite materials can also give parts complex geometric appearances to meet specific load capacities. This is a goal that cannot be achieved at low cost for traditional processes. Imagine that if chopped fibers are used as raw materials, supplemented by a fast process such as injection molding with less human intervention, the parts produced will have a low cost, but will not have sufficient load capacity; on the contrary, if continuous fibers are used as raw materials, supplemented by a slow process with frequent human intervention, the parts produced will have sufficient load capacity, but the cost will be very high.
Based on the existence of the above contradictions, the composites industry has invested huge resources in the intention to develop an automated production process that is both efficient and low-cost, while giving parts a higher load capacity to meet the specific needs of customers in the aerospace field. Against this background, after consultation between Victrex and Tri-Mack, TxV was officially established in 2017 with the mission of promoting the aviation application of PAEK-based composites.
Virtual prototyping: Without actually producing samples, TxV can repeatedly verify the placement and ply orientation until the load capacity meets the design requirements.
The hybrid composite molding process launched by TxV has two key advantages. First, the continuous fiber reinforcement of the part is automated; second, the high efficiency of the injection molding process is fully utilized to achieve complex geometries. It is important to emphasize that in achieving the above goals, TxV first produces laminates that meet the load requirements, and then performs composite molding to achieve its functionalization and give it the final geometry. Sascha Costabel, director of innovation at SFS intec, said: "The new process introduced by TxV is a good choice compared to the traditional process that requires a series of operations to achieve the high load capacity and complex geometry of the parts."
Sourkes said that TxV regards SFS as a partner of "... As a system accessory product..., SFS has a consistent interest in new technologies. They have an innovative spirit and a strong willingness to invest in new technologies." In addition, SFS intec maintains close contact with aviation customers and has "qualifications". This is very important for redesigned aviation parts.
The aircraft luggage compartment bracket, also known as the "B bracket", was selected as an aviation accessory product to be redesigned using composite materials because of its extremely challenging design and production. With the help of finite element analysis tools provided by Altair, the project team has repeatedly tested, verified and finally proved the success of the model through joint engineering design, product concept design and model design from the first sample. TxV said that the key to research and development lies in adhering to the concept of "design for production" and making full use of the advantages of continuous fiber automatic laying technology and short-cut fiber high-speed injection molding technology.
Production of B bracket
In the hybrid material composite molding process, multiple polymer raw materials of the same grade and different types with outstanding characteristics are used. For example, PAEK is used in conjunction with the continuous fiber reinforcement part, while PEEK is used in the composite molding peripheral part. Both PAEK and PEEK products are provided by Victrex and have excellent fatigue resistance, chemical corrosion resistance, pyrotechnic toxicity resistance, rapid prototyping and excellent weldability. Among them, VICTREX AE 250 is a low-melting PAEK material (LM PAEK), which has a melting point 40 degrees Celsius lower than PEEK. "When the molten PEEK flows over the surface of the LM PAEK composite material, the two will be better fused together."
The key raw materials used in the production of B bracket include: unidirectional carbon fiber/PAEK prepreg tape with a width of 2 inches (carbon fiber content 58%) under the brand name VICTREX AE 250 and short-fiber PEEK molding compound (carbon fiber content 30%) under the brand name VICTREX PEEK 150CA30. After these raw materials are fed into the mixed material composite molding production unit, they are gradually formed through the following steps:
The first step is to lay the carbon fiber/PAEK prepreg tape using the Fiberforge 2000 tape laying system provided by Dieffenbacher. "This is one of the fastest tape laying systems on the market," said Sourkes. It can be used in conjunction with a robot to load and lay prepreg tapes without interruption. The entire layup process has been carefully designed to minimize the porosity between the prepreg tapes. At the same time, each layer is re-tested before being laid. The above process is carried out in a strictly controlled environment, without interference from foreign debris and debris (FOD).
Step 1: The blank is produced using the Dieffenbacher Fiberforge 2000 automatic tape laying machine.
Second, after the layup is completed, the blank is sent to the automatic molding unit. First, a set of heated press plates are used to compact and remove internal pores; then a set of cold press plates are used to cool the blank. This "one cold and one hot" two-set press plate operation method is more efficient than simply using one set of press plates. "The direct benefit is that the production cycle of the parts can be reduced from hours to minutes." Sourkes said.
Step 2: The blank enters the automatic molding unit and is compacted and cooled by two sets of press plates, one hot and one cold.
In the third step, after compaction, the preform is formed and sent to the next work unit to complete the initial shape of the bracket.
Step 3: The initial shape of bracket B is completed
Step 4: The preform is cut with a water jet provided by Flow International to produce carbon fiber/PAEK inserts.
"Each project requires a trade-off in the size of the preform." Sourkes pointed out, "If calculated properly, 3-4 rectangular inserts can be cut out of a preform. This can effectively reduce waste, but it will increase the operation time of water jet cutting accordingly." Taking bracket B as an example, several small inserts can be cut out of a preform.
Step 4: Cut the blank with a water jet to cut out the carbon fiber/PAEK insert. Two such inserts are required on each bracket.
Step 5: Use a high-temperature injection molding machine provided by ENGEL for composite molding. The insert is placed in the injection molding machine cavity and injected with molten PEEK. Since the insert is made of PAEK LM, which has a low melting point, the surface part will be tightly bonded to the molten PEEK.
Step 5: Composite molding using an Engel high-temperature injection molding machine
In the sixth step, if necessary, the injection molded parts can be machined until they reach a net shape. "Although our goal is to achieve a near-net shape," Soukers explained, "in most cases, a small degree of machining is required to ensure that the actual geometric appearance of the product is accurate to the design." This part of the operation is usually completed using a water jet or on a CNC machining center.
Breakthrough
In the production of the B bracket, the mixed material composite molding process successfully controlled the production cycle to 3 minutes and the BTF value to 1.06:1 (the scrap rate was about 5.7%). "With this technology, raw materials are fully utilized, production efficiency is improved, we provide customers with high value-added thermoplastic composite parts, and reduce the design cost of metal parts." The production results show that the weight of the B bracket has dropped by 30%-40%, the production cost has been saved by 20%-30%, and its geometric appearance and various parameter performance have reached the level of existing metal parts. "If we are given an opportunity to completely redesign the component system, the weight reduction rate can reach 60%."
In addition, this carbon fiber/PAEK/PEEK luggage compartment bracket also effectively reduces the number of parts. Previously, the supporting base of the bracket was made of PEEK material and fixed to the bottom of the bracket by two rivets. Now, TxV and SFS have agreed to use the same composite molding process to directly composite a base at the bottom of the bracket.
There is no doubt that the success of the hybrid material composite molding process is inseparable from the technical support of the two shareholders behind TxV. Sourkes explained that after completing the development of PAEK materials and related processes, Victrex first looked for cooperation opportunities among existing partners. "However, companies that know how to mold plastics often don't have the ability to process continuous fibers, and companies that know how to process continuous fibers often know little about the injection molding process." Due to this constraint, Victrex and Tri-Mack have been working together on these two key technical points for many years before TxV and the Polyketone Composites Innovation Center were established.
When asked to compare the hybrid composite molding process with the traditional process, Soukes said that the traditional process could not repair the B bracket, especially from a cost perspective.
First flight
With the advantage of SFS intec's qualification, the two parties have applied for a separate airworthiness for this B bracket. "Because the B bracket needs to be installed overhead, it is easy to reach the rated load during use." Sourkes said, "Especially during takeoff and landing, the actual load will be greater." TxV and SFS hope that this part can be put on the plane in early 2020.
Once airworthiness is obtained, TxV will start mass production of the B bracket. Sourkes emphasized that TxV can use its own production line for production, and is willing to provide technical support to interested potential partners to use their production lines for production.
This B bracket product is expected to open up a wider market for similar composite products. According to forecasts, a civil aircraft will require thousands of brackets and other system accessories. Once composite materials are adopted, these products will help aircraft
Typically, aerospace companies are willing to pay more for more suitable composite parts because they know that such efforts will pay off. Because of its light weight, it can reduce fuel consumption; because of its durability, it has a longer service life and reduces operating costs. This "full life cycle" perspective opens the door to many terminal application markets for composite materials. However, even with all the above advantages, its cost disadvantage is obvious. It is well known that under current conditions, the production cost of composite parts is much higher than that of metal materials.
However, this situation is quietly changing.
The new composite automated production technology launched by TxV Aero Composites in the United States is tilting the low-cost balance towards composite materials. This technology is called "hybrid composite molding process."
TxV Aero Composites is a joint venture between Tri-Mack Plastics Manufacturing and Victrex. Its hybrid composite molding process has been aimed at commercial-scale mass production since its launch. TxV has now partnered with SFS intec Aircraft Components of Germany (hereinafter referred to as SFS intec) to abandon the previously used aviation aluminum materials and redesign the composite aircraft luggage compartment bracket products, which have the ability to be mass-produced. The successful launch of this product shows the potential of hybrid composite molding process and Victrex's carbon fiber/PAEK unidirectional prepreg tape product named VICTREX AE 250 in many aviation fields. If the production of traditional metal parts is called a "subtractive process", then the production of composite parts can be called an "additive process".
From "subtractive" to "additive"
Machinists often jokingly call themselves "waste making machines" because a lot of debris and waste are generated in the process of processing metal sheets into metal parts. They are either recycled, processed, or immediately put back into production. But no matter which method is used, it cannot change the fact of waste, and it directly increases production costs. It is said that taking the aluminum bracket of the aircraft luggage compartment produced by SFS intec as an example, after a series of machining links, the scrap rate is as high as 60%-70%.
Because of such a high scrap rate, the cost of composite materials is lower than that of aluminum, whether it is a net shape or a near net shape bracket, only from the perspective of raw materials. "Although aluminum is cheaper, the high scrap rate gives composite materials an opportunity to compete from a cost perspective. Especially when the BTF ratio (buy-to-fly ratio) reaches 8:1 (the scrap rate is as high as 87.5%), most of the purchased aluminum is wasted." Jonathan Sourkes, account manager of TxV, said, "In addition, from the perspective of production cycle, composite materials are also very advantageous. It can shorten the production cycle from hours to minutes."
In addition, composite materials can also give parts complex geometric appearances to meet specific load capacities. This is a goal that cannot be achieved at low cost for traditional processes. Imagine that if chopped fibers are used as raw materials, supplemented by a fast process such as injection molding with less human intervention, the parts produced will have a low cost, but will not have sufficient load capacity; on the contrary, if continuous fibers are used as raw materials, supplemented by a slow process with frequent human intervention, the parts produced will have sufficient load capacity, but the cost will be very high.
Based on the existence of the above contradictions, the composites industry has invested huge resources in the intention to develop an automated production process that is both efficient and low-cost, while giving parts a higher load capacity to meet the specific needs of customers in the aerospace field. Against this background, after consultation between Victrex and Tri-Mack, TxV was officially established in 2017 with the mission of promoting the aviation application of PAEK-based composites.
Virtual prototyping: Without actually producing samples, TxV can repeatedly verify the placement and ply orientation until the load capacity meets the design requirements.
The hybrid composite molding process launched by TxV has two key advantages. First, the continuous fiber reinforcement of the part is automated; second, the high efficiency of the injection molding process is fully utilized to achieve complex geometries. It is important to emphasize that in achieving the above goals, TxV first produces laminates that meet the load requirements, and then performs composite molding to achieve its functionalization and give it the final geometry. Sascha Costabel, director of innovation at SFS intec, said: "The new process introduced by TxV is a good choice compared to the traditional process that requires a series of operations to achieve the high load capacity and complex geometry of the parts."
Sourkes said that TxV regards SFS as a partner of "... As a system accessory product..., SFS has a consistent interest in new technologies. They have an innovative spirit and a strong willingness to invest in new technologies." In addition, SFS intec maintains close contact with aviation customers and has "qualifications". This is very important for redesigned aviation parts.
The aircraft luggage compartment bracket, also known as the "B bracket", was selected as an aviation accessory product to be redesigned using composite materials because of its extremely challenging design and production. With the help of finite element analysis tools provided by Altair, the project team has repeatedly tested, verified and finally proved the success of the model through joint engineering design, product concept design and model design from the first sample. TxV said that the key to research and development lies in adhering to the concept of "design for production" and making full use of the advantages of continuous fiber automatic laying technology and short-cut fiber high-speed injection molding technology.
Production of B bracket
In the hybrid material composite molding process, multiple polymer raw materials of the same grade and different types with outstanding characteristics are used. For example, PAEK is used in conjunction with the continuous fiber reinforcement part, while PEEK is used in the composite molding peripheral part. Both PAEK and PEEK products are provided by Victrex and have excellent fatigue resistance, chemical corrosion resistance, pyrotechnic toxicity resistance, rapid prototyping and excellent weldability. Among them, VICTREX AE 250 is a low-melting PAEK material (LM PAEK), which has a melting point 40 degrees Celsius lower than PEEK. "When the molten PEEK flows over the surface of the LM PAEK composite material, the two will be better fused together."
The key raw materials used in the production of B bracket include: unidirectional carbon fiber/PAEK prepreg tape with a width of 2 inches (carbon fiber content 58%) under the brand name VICTREX AE 250 and short-fiber PEEK molding compound (carbon fiber content 30%) under the brand name VICTREX PEEK 150CA30. After these raw materials are fed into the mixed material composite molding production unit, they are gradually formed through the following steps:
The first step is to lay the carbon fiber/PAEK prepreg tape using the Fiberforge 2000 tape laying system provided by Dieffenbacher. "This is one of the fastest tape laying systems on the market," said Sourkes. It can be used in conjunction with a robot to load and lay prepreg tapes without interruption. The entire layup process has been carefully designed to minimize the porosity between the prepreg tapes. At the same time, each layer is re-tested before being laid. The above process is carried out in a strictly controlled environment, without interference from foreign debris and debris (FOD).
Step 1: The blank is produced using the Dieffenbacher Fiberforge 2000 automatic tape laying machine.
Second, after the layup is completed, the blank is sent to the automatic molding unit. First, a set of heated press plates are used to compact and remove internal pores; then a set of cold press plates are used to cool the blank. This "one cold and one hot" two-set press plate operation method is more efficient than simply using one set of press plates. "The direct benefit is that the production cycle of the parts can be reduced from hours to minutes." Sourkes said.
Step 2: The blank enters the automatic molding unit and is compacted and cooled by two sets of press plates, one hot and one cold.
In the third step, after compaction, the preform is formed and sent to the next work unit to complete the initial shape of the bracket.
Step 3: The initial shape of bracket B is completed
Step 4: The preform is cut with a water jet provided by Flow International to produce carbon fiber/PAEK inserts.
"Each project requires a trade-off in the size of the preform." Sourkes pointed out, "If calculated properly, 3-4 rectangular inserts can be cut out of a preform. This can effectively reduce waste, but it will increase the operation time of water jet cutting accordingly." Taking bracket B as an example, several small inserts can be cut out of a preform.
Step 4: Cut the blank with a water jet to cut out the carbon fiber/PAEK insert. Two such inserts are required on each bracket.
Step 5: Use a high-temperature injection molding machine provided by ENGEL for composite molding. The insert is placed in the injection molding machine cavity and injected with molten PEEK. Since the insert is made of PAEK LM, which has a low melting point, the surface part will be tightly bonded to the molten PEEK.
Step 5: Composite molding using an Engel high-temperature injection molding machine
In the sixth step, if necessary, the injection molded parts can be machined until they reach a net shape. "Although our goal is to achieve a near-net shape," Soukers explained, "in most cases, a small degree of machining is required to ensure that the actual geometric appearance of the product is accurate to the design." This part of the operation is usually completed using a water jet or on a CNC machining center.
Breakthrough
In the production of the B bracket, the mixed material composite molding process successfully controlled the production cycle to 3 minutes and the BTF value to 1.06:1 (the scrap rate was about 5.7%). "With this technology, raw materials are fully utilized, production efficiency is improved, we provide customers with high value-added thermoplastic composite parts, and reduce the design cost of metal parts." The production results show that the weight of the B bracket has dropped by 30%-40%, the production cost has been saved by 20%-30%, and its geometric appearance and various parameter performance have reached the level of existing metal parts. "If we are given an opportunity to completely redesign the component system, the weight reduction rate can reach 60%."
In addition, this carbon fiber/PAEK/PEEK luggage compartment bracket also effectively reduces the number of parts. Previously, the supporting base of the bracket was made of PEEK material and fixed to the bottom of the bracket by two rivets. Now, TxV and SFS have agreed to use the same composite molding process to directly composite a base at the bottom of the bracket.
There is no doubt that the success of the hybrid material composite molding process is inseparable from the technical support of the two shareholders behind TxV. Sourkes explained that after completing the development of PAEK materials and related processes, Victrex first looked for cooperation opportunities among existing partners. "However, companies that know how to mold plastics often don't have the ability to process continuous fibers, and companies that know how to process continuous fibers often know little about the injection molding process." Due to this constraint, Victrex and Tri-Mack have been working together on these two key technical points for many years before TxV and the Polyketone Composites Innovation Center were established.
When asked to compare the hybrid composite molding process with the traditional process, Soukes said that the traditional process could not repair the B bracket, especially from a cost perspective.
First flight
With the advantage of SFS intec's qualification, the two parties have applied for a separate airworthiness for this B bracket. "Because the B bracket needs to be installed overhead, it is easy to reach the rated load during use." Sourkes said, "Especially during takeoff and landing, the actual load will be greater." TxV and SFS hope that this part can be put on the plane in early 2020.
Once airworthiness is obtained, TxV will start mass production of the B bracket. Sourkes emphasized that TxV can use its own production line for production, and is willing to provide technical support to interested potential partners to use their production lines for production.
This B bracket product is expected to open up a wider market for similar composite products. According to forecasts, a civil aircraft will require thousands of brackets and other system accessories. Once composite materials are adopted, these products will help aircraft
