Final Report Summary - COSPI (Composite Stiffened Panels Infusion)
Executive Summary:
The CoSPI project aims at developing and manufacturing flat stiffened skin composite panel using infusion process. This kind of process often leads to the reduction of manufacturing costs while lessening the environmental impact of the production. Three different processes have been studied: cold infusion, Liquid Resin Infusion and Resin Film infusion. The major development efforts have been on the impact behaviour. This behaviour is a critical issue for parts obtained by infusion and has to be acceptable for primary structure parts. Several parameters have been studied such as the resins, the preform type, the curing in an oven or an autoclave, in order to optimise the triptych process-composite preform-resin. Thus a trade-off study have been carried out in order to choose the best infusion process in terms of mechanical behaviour, costs and environmental impact. Minimize waste is a key issue in composite processes. These wastes have been identified and quantified during the project.
Three partners are part of this project: UBO a French university, CC a Swiss SME and FMC a French SME. UBO has a wide experience of infusion
processes and has already been part of projects on this topic. FMC and CC are two SMEs specialised in high technology composite parts manufacturing.
The trade-off study led to the conclusion that out-of-autoclave Liquid Resin Infusion process with powdered preforms was the the best compormise to optimise the triptych process-composite preform-resin. This process have been compared to well known prepregs resins cured in autoclave. The mechanical results on static and impact tests have shown that out-of-autoclave LRI process can meet the standards required for primary structure parts. Thus final demonstrators were manufactured using this process and the selected resin (PRISM EP2400 by Cytec). Those demonstrators are blade and J stiffened panels representing a fuselage section. Their dimensions are 1200x750mm with 5 stiffeners.
Project Context and Objectives:
WP2 Trade-off study:
The objectives are to carry out a trade-off between Resin Film Infusion (RFI) and Liquid Infusion (LI) in terms of feasibility, ecological impact, costs and mechanical characteristics.
Two main tasks will be conducted in this Work Package:
• Manufacture the coupons
• Test their mechanical behaviour
The influence of several parameters will be studied in order to optimise the triptych process-composite preform-resin. These parameters are 6 processes (cold infusion, LRI, RFI with or without using an autoclave), 8 resins and 2 different ways to obtain the preforms (stitched or powdered). First, one resin will be chosen for each infusion technique (cold infusion, LRI, RFI). Then stiffened coupons will be manufactured and tested in order to make the final choice for this trade-off study.
Task 3.3 Two panels manufacturing and inspection using selected material and process (UBO, To+16 - To +23)
Finally, the two required panels will be manufactured according to the geometric specifications provided. The manufactured panels will then be inspected using Non Destructive Testing techniques in order to validate the chosen parameters.
Task 2.1 Feasibility study and coupons manufacturing plan (UBO, To – To+1)
Feasibility study and coupons manufacturing plan. 44 coupons need to be manufactured and this work will be split between FMC and CC. All the processes which require an autoclave will be done at FMC in France. The others will be manufactured at CC in Switzerland. UBO will be in charge of the work plan and will supply the manufacturers with the same resins and consumables.
Task 2.2 Study of the process parameters and selection of composite and resin materials (CC,
To+1 – To+2)
Many parameters need to be adjusted in order to optimise the infusion processes. CC will be in charge of this task, and will, in particular, choose the temperatures for the infusion, the exact resin quantities, etc. The parameters of the autoclave for the processes involved will be chosen by FMC.
Task 2.3 Flat Coupons manufacturing (CC, To+2 – To+3)
RFI and LI coupons will be manufactured by CC with previously defined parameters (16 coupons) Autoclave-treated RFI and LI coupons will be manufactured by FMC (16 coupons)
WP3 Stiffened panels manufacturing
The objective is to manufacture two flat stiffened skin composite panels reinforced with J and blade section stringers by using the results carried out by WP2.
Task 3.1 Study and manufacturing of dry composite preform to reduce manufacturing waste (UBO, To+9 – To+12)
At the beginning of this WP, the process and the materials are chosen. Thus, the efforts will be on the design of the preforms in order to minimise waste.
Task 3.2 Optimisation of the selected infusion process parameters (UBO, To+12 – To+16)
Task 3.3 Two panels manufacturing and inspection using selected material and process (UBO, To+16 - To +23)
Project Results:
Overview of the mechanical tests:
Traction ASTM D3039 on:
- UD 0°
- UD 90°
- Quasi-isotropic lay-up
Filled-Hole Tension test (ASTM D672)
Compression ASTM D695 test on:
- UD 0°
- UD 90°
- Quasi-isotropic lay up
Open Hole Compression test (ASTM D6484)
Compression After Impact test (ASTM D7137)
These tests have been performed on each couple resin/process. Moreover, each couple has been cured either in an oven or in an autoclave. Thus 16 couples have been tested.
Conclusions of the tests
The tests realized represent 880 coupons. Many data have been generated and the first conclusions will focus on the choice of the resin for each process: RFI, LRI and cold infusion.
Resin Film Infusion
The panels manufactured by Resin Film Infusion show an important difference on the mechanical behaviour between those cured in an oven and those cured in an autoclave with additional pressure. With the tested resins, poor results are obtained when the curing is performed in an oven under atmospheric pressure. On the contrary, panels cured in an autoclave showed high mechanical properties. These panels could be considered as a reference because the RFI process in autoclave could be assimilated as prepreg process. The products are similar and the curing methods are also very close.
Concerning the choice between the two tested resin films (M21 and M36), their behaviour is different depending on the test considered. The results on M36 show stiffer coupons in traction and compression. The shear modulus is also higher with M36 resin. Concerning the ultimate stress, the results are close for the two resins with a better result for the M21 on traction 90° tests.
Finally, the compression after impact test revealed that the M21 resin has a better impact resistance with a significantly higher residual compression stress.
Thus, as good impact behaviour is sought in this study, the M21 resin film cured in an autoclave has been chosen for the remainder of the study.
Liquid Resin Infusion
The choice of the resin for this process is quite easy even if 3 resins have been tested. The Prism EP2400 resin from Cytec shows higher results than the other two resins in all the tests. For this process, results have shown that the autoclave do not improve the mechanical behaviour of the panels. The performances can even decrease for some tests with the Cytec resin.
Cold infusion
As for Liquid Resin Infusion process, one of the three resins tested with cold infusion process presents a better mechanical behaviour. This resin is the resoltech HTG160. The curing in an autoclave of this resin do not bring significant changes on the test results whereas epolam resin results are improved by this curing method.
Finally Resoltech HTG 160 resin has been chosen for stiffened panels manufactured by cold infusion. Nevertheless, this resin is difficult to infuse as it is very viscous at room temperature.
Overall comparison
RFI panels cured in autoclave can be seen as reference for mechanical properties as the products used and the process is similar to autoclave prepreg panels. Thus the 2 selected resins for LRI and cold infusion can be compared to M21 panels cured in an autoclave. We observed that the results obtained with Prism EP2400 resin from Cytec are really closed to the reference results. Resoltech HTG160 present also interesting mechanical results but they are slightly below RFI M21 cured in autoclave and LRI Cytec. This is especially the case for traction test on UD 90°. Moreover, even if cold infusion is less a less energy consuming process, Resoltech HTG160 is difficult to infuse due to its low viscosity. Thus, more infusion products should be used to infuse large parts and the risk of having dry spots is higher.
For final panels manufacturing, powdered performs have been retained instead of knitted performs. As discussed in the report D2.3 they are obtained by pressing the fabrics between two angles in a vacuum bag.
The final panels are manufactured by Liquid Resin Infusion using the Cytec Prism EP2400 resin. The infusion strategy retained for infusing the stiffened panels is from below with microporous membrane as for the final blade stiffened panel. The infusion strategy has been detailed in Deliverable D2.3.
Potential Impact:
Dissemination activities have been conducted during the project.
Some results have been presented during two conferences on composite materials:
JNC18, Nantes, France
ICCM19, Montreal, Canada
List of Websites:
Contact details:
Dr. Thomas Bonnemains
IUT de BREST/LBMS
rue de Kergoat - CS 93837
29238 BREST CEDEX 3
The CoSPI project aims at developing and manufacturing flat stiffened skin composite panel using infusion process. This kind of process often leads to the reduction of manufacturing costs while lessening the environmental impact of the production. Three different processes have been studied: cold infusion, Liquid Resin Infusion and Resin Film infusion. The major development efforts have been on the impact behaviour. This behaviour is a critical issue for parts obtained by infusion and has to be acceptable for primary structure parts. Several parameters have been studied such as the resins, the preform type, the curing in an oven or an autoclave, in order to optimise the triptych process-composite preform-resin. Thus a trade-off study have been carried out in order to choose the best infusion process in terms of mechanical behaviour, costs and environmental impact. Minimize waste is a key issue in composite processes. These wastes have been identified and quantified during the project.
Three partners are part of this project: UBO a French university, CC a Swiss SME and FMC a French SME. UBO has a wide experience of infusion
processes and has already been part of projects on this topic. FMC and CC are two SMEs specialised in high technology composite parts manufacturing.
The trade-off study led to the conclusion that out-of-autoclave Liquid Resin Infusion process with powdered preforms was the the best compormise to optimise the triptych process-composite preform-resin. This process have been compared to well known prepregs resins cured in autoclave. The mechanical results on static and impact tests have shown that out-of-autoclave LRI process can meet the standards required for primary structure parts. Thus final demonstrators were manufactured using this process and the selected resin (PRISM EP2400 by Cytec). Those demonstrators are blade and J stiffened panels representing a fuselage section. Their dimensions are 1200x750mm with 5 stiffeners.
Project Context and Objectives:
WP2 Trade-off study:
The objectives are to carry out a trade-off between Resin Film Infusion (RFI) and Liquid Infusion (LI) in terms of feasibility, ecological impact, costs and mechanical characteristics.
Two main tasks will be conducted in this Work Package:
• Manufacture the coupons
• Test their mechanical behaviour
The influence of several parameters will be studied in order to optimise the triptych process-composite preform-resin. These parameters are 6 processes (cold infusion, LRI, RFI with or without using an autoclave), 8 resins and 2 different ways to obtain the preforms (stitched or powdered). First, one resin will be chosen for each infusion technique (cold infusion, LRI, RFI). Then stiffened coupons will be manufactured and tested in order to make the final choice for this trade-off study.
Task 3.3 Two panels manufacturing and inspection using selected material and process (UBO, To+16 - To +23)
Finally, the two required panels will be manufactured according to the geometric specifications provided. The manufactured panels will then be inspected using Non Destructive Testing techniques in order to validate the chosen parameters.
Task 2.1 Feasibility study and coupons manufacturing plan (UBO, To – To+1)
Feasibility study and coupons manufacturing plan. 44 coupons need to be manufactured and this work will be split between FMC and CC. All the processes which require an autoclave will be done at FMC in France. The others will be manufactured at CC in Switzerland. UBO will be in charge of the work plan and will supply the manufacturers with the same resins and consumables.
Task 2.2 Study of the process parameters and selection of composite and resin materials (CC,
To+1 – To+2)
Many parameters need to be adjusted in order to optimise the infusion processes. CC will be in charge of this task, and will, in particular, choose the temperatures for the infusion, the exact resin quantities, etc. The parameters of the autoclave for the processes involved will be chosen by FMC.
Task 2.3 Flat Coupons manufacturing (CC, To+2 – To+3)
RFI and LI coupons will be manufactured by CC with previously defined parameters (16 coupons) Autoclave-treated RFI and LI coupons will be manufactured by FMC (16 coupons)
WP3 Stiffened panels manufacturing
The objective is to manufacture two flat stiffened skin composite panels reinforced with J and blade section stringers by using the results carried out by WP2.
Task 3.1 Study and manufacturing of dry composite preform to reduce manufacturing waste (UBO, To+9 – To+12)
At the beginning of this WP, the process and the materials are chosen. Thus, the efforts will be on the design of the preforms in order to minimise waste.
Task 3.2 Optimisation of the selected infusion process parameters (UBO, To+12 – To+16)
Task 3.3 Two panels manufacturing and inspection using selected material and process (UBO, To+16 - To +23)
Project Results:
Overview of the mechanical tests:
Traction ASTM D3039 on:
- UD 0°
- UD 90°
- Quasi-isotropic lay-up
Filled-Hole Tension test (ASTM D672)
Compression ASTM D695 test on:
- UD 0°
- UD 90°
- Quasi-isotropic lay up
Open Hole Compression test (ASTM D6484)
Compression After Impact test (ASTM D7137)
These tests have been performed on each couple resin/process. Moreover, each couple has been cured either in an oven or in an autoclave. Thus 16 couples have been tested.
Conclusions of the tests
The tests realized represent 880 coupons. Many data have been generated and the first conclusions will focus on the choice of the resin for each process: RFI, LRI and cold infusion.
Resin Film Infusion
The panels manufactured by Resin Film Infusion show an important difference on the mechanical behaviour between those cured in an oven and those cured in an autoclave with additional pressure. With the tested resins, poor results are obtained when the curing is performed in an oven under atmospheric pressure. On the contrary, panels cured in an autoclave showed high mechanical properties. These panels could be considered as a reference because the RFI process in autoclave could be assimilated as prepreg process. The products are similar and the curing methods are also very close.
Concerning the choice between the two tested resin films (M21 and M36), their behaviour is different depending on the test considered. The results on M36 show stiffer coupons in traction and compression. The shear modulus is also higher with M36 resin. Concerning the ultimate stress, the results are close for the two resins with a better result for the M21 on traction 90° tests.
Finally, the compression after impact test revealed that the M21 resin has a better impact resistance with a significantly higher residual compression stress.
Thus, as good impact behaviour is sought in this study, the M21 resin film cured in an autoclave has been chosen for the remainder of the study.
Liquid Resin Infusion
The choice of the resin for this process is quite easy even if 3 resins have been tested. The Prism EP2400 resin from Cytec shows higher results than the other two resins in all the tests. For this process, results have shown that the autoclave do not improve the mechanical behaviour of the panels. The performances can even decrease for some tests with the Cytec resin.
Cold infusion
As for Liquid Resin Infusion process, one of the three resins tested with cold infusion process presents a better mechanical behaviour. This resin is the resoltech HTG160. The curing in an autoclave of this resin do not bring significant changes on the test results whereas epolam resin results are improved by this curing method.
Finally Resoltech HTG 160 resin has been chosen for stiffened panels manufactured by cold infusion. Nevertheless, this resin is difficult to infuse as it is very viscous at room temperature.
Overall comparison
RFI panels cured in autoclave can be seen as reference for mechanical properties as the products used and the process is similar to autoclave prepreg panels. Thus the 2 selected resins for LRI and cold infusion can be compared to M21 panels cured in an autoclave. We observed that the results obtained with Prism EP2400 resin from Cytec are really closed to the reference results. Resoltech HTG160 present also interesting mechanical results but they are slightly below RFI M21 cured in autoclave and LRI Cytec. This is especially the case for traction test on UD 90°. Moreover, even if cold infusion is less a less energy consuming process, Resoltech HTG160 is difficult to infuse due to its low viscosity. Thus, more infusion products should be used to infuse large parts and the risk of having dry spots is higher.
For final panels manufacturing, powdered performs have been retained instead of knitted performs. As discussed in the report D2.3 they are obtained by pressing the fabrics between two angles in a vacuum bag.
The final panels are manufactured by Liquid Resin Infusion using the Cytec Prism EP2400 resin. The infusion strategy retained for infusing the stiffened panels is from below with microporous membrane as for the final blade stiffened panel. The infusion strategy has been detailed in Deliverable D2.3.
Potential Impact:
Dissemination activities have been conducted during the project.
Some results have been presented during two conferences on composite materials:
JNC18, Nantes, France
ICCM19, Montreal, Canada
List of Websites:
Contact details:
Dr. Thomas Bonnemains
IUT de BREST/LBMS
rue de Kergoat - CS 93837
29238 BREST CEDEX 3