LF Technology - unique epoxy foil
What is LF Technology?
The LETOXIT® Foil Technology (LF Technology) is our unique patented technology, which allows dry way of laminate production based on the impregnation of reinforcement with LETOXIT® foil resin at increased temperature and pressure.
Prepregs are materials used for years, but they are very expensive and many prepreg types are necessary, if composite structure should be optimised well. RTM is a relatively cheap method, big parts can be manufactured. The main problem is impregnation of the reinforcement. Therefore only special types of the reinforcement have to be used and the result is relatively low reinforcement content in a final composite part. In recent years, technology called RFI – Resin Film infusion appeared. The production cycle is performed usually in the autoclave under increased temperature and pressure, where the fibre infiltration and the composite consolidation occur in a single step process. Typically, the RFI element consists of a thermoset resin film placed between one side of a metal tool and a dry textile fibre preform. Problems with conventional RFI appear if sandwich structures are manufactured; honeycombs are filled with resin and foam prevents from impregnation of the sandwich skin in opposite site of the resin layer.
LF Technology SCHEME
Concerning these disadvantages of conventional processes and a need of universal low cost technology, 5M s.r.o. developed and patented a very efficient technique of production of sophisticated and relatively cheap composite structures, which is called Letoxit Foil Technology (LF Technology).
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LF TECHNOLOGY is epoxy resin in the form of flexible foil, which softens at increased temperature and it is able to impregnate originally dry reinforcement and cure in one step. |
During manipulation, production and curing doesnt release any hazard vapours and foil is very friendly to use.
LF Technology allows the application of various types and numbers of layers at different places of the construction.
The products made by the LF Technology are comparable with products made by the prepreg technology. In comparison with prepregs has LF Technology big advantage in variability, i.e. in production can be used dry fabric as required (the same like in usual hand lay-up) and that saves money, because there is no need to store huge amount of prepregs in freezer.
Advantages:
- substite for prepregs with better logistics conditions - reinforcement you can choose, in freezer store only resin
- variability of reinforcement
- dry way of lamination
- 3x faster production compare with liquid resins
- impregnation and curing in one step
- great ratio resin/reinforcement (40:60)
- very nice and smooth surface
- no hazard vapours
- very friendly to use
- accurate defined composite structure in everyposition in the final product
Practical information about application and working with LF Technology you can find in this article, which was issued in magazine Czech aerospace processing (covered by Aeronatical research and test institute)
Technical data
| Possible reinforcement |
|
| Area weight | 120 g/m2 - 840 g/m2 |
| Curing temperature |
|
| Required vaccum | 0,075 - 0,09 MPa |
| Roll width |
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| Possible core material |
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Whole product range covers many types with different characteristics, for example there are types with high temperature resistance (250°C), or fulfils FAR 25 and FAR 23 standards, or type developed specially for lamination of carbon fabrics.
LETOXIT® Foil
| TYPE | RESIN | CURING TEMP. | CURING TIME |
Max. Tg |
DESCRIPTION |
| LFX 023 | epoxy | 120°C | 60 min. | 100°C | basic type |
| LFX 035 | epoxy | 120°C | 60 min. | 125°C | low viscosity, for carbon fabrics |
| LFX 038 | halogenated epoxy | 120°C | 60 min. | 135°C | self extinguishing (FAR 23) |
| LFX 040 | modificated kyanoester | 120°C | 60 min. | 250°C | high Tg |
| LFX 044 | modificated epoxy | 120°C | 60 min. | 105°C | high impact strength |
| LFX 054 | epoxy | 120°C | 60 min. | 155°C | higher Tg, low viscosity |
| LFX 055 | epoxy | 120°C | 60 min. | 155°C | higher Tg, low stickiness |
| LFX 056 | epoxy | 120°C | 60 min. | 125°C | self extinguishing (FAR 25) |
| LFX 060 | epoxy | 80°C | 240 min. | 125°C | curing at 80°C, low viscosity (for carbon) |
|
NEW! LFX 062 |
phenolic | 120°C | 45 min. | 103°C | self extinguishing (DIN 5510-2) |
| LFX 162 | epoxy | 80°C | 240 min. | 100°C | low curing temp., higher stickiness |
LF Technology - technical data
Application
LF Technology is suitable for any composite structure, where balanced weight and mechanical properties ratio are required. Typical applications are tin shell structures with high reinforcement volume, locally added reinforcements and/or with different required local properties (for example reinforcement orientation) because these structures cannot be manufactured by conventional technologies without highadded cost of material and work. The conventional composite structures, originally made by RTM, VARTM, Hand-lay up, are possible, of course. but due to lower requirements on mechanical properties on parts made by these conventional technologies, economy of LF technology (RFI) must be taken into account.
Potential applications are:
- Automotive – car bodies, covers, hoods
- Transportation – hoods, side panels, doors, racks
- Aerospace – covers, doors and all types of panels
- Building – tables, eye-catchers
- Medical – orthosis and prosthesis
Sample 1:
First application was an engine hood of ultralight aeroplane prototype CHS 701SP (producer Czech Aircraft Works), originally composite part made by hand-lay up from unsaturated polyester resin. 40% weight decrease was achieved using LF Technology This weight decrease appears and the same stiffness remains due to use of local reinforcement with Nomex honeycombs in the top of the hood. Foam was applied in the upper part. Other important benefit was higher thermal stability. Good surface of the part was achieved although gelcoat was not applied.
Sample 2:
Equipment for VIP cabin of aircraft M101T EXPEDITION, producer MYASISHCHEV - refreshment box made from LF Technology and Nomex honeycom core
Sample 3:
Box for transport of people infected by highly infectious diseases made by LF Technology using Letoxit LFX 038 and Nomex honeycomb core
Download
LF Technology - leaflet (672 kB)
LF Technology - technical data (409 kB)
LF Technology - article in Czech aerospace proceedings (1,2 MB)
LF Technology - FAR 23 declaration for LFX 038 (147 kB)
LF Technology - Innovation of the year 2005 (only in Czech) (264 kB)
LF Technology - article in Composite solutions magazine (1,1 MB)






21.12.2011


