IMPROVEMENTS IN OR RELATING TO INFUSION MOULDING

Abstract

The invention relates to a resin infusion process wherein a curable flowing fluid resin composition is supplied to form a curable matrix around a fibrous reinforcement material, wherein the curable flowing fluid resin composition comprises a resin component (1) and an activator component (2), and at least one property of the curable flowing fluid resin composition is monitored prior to supply.

Claims

1. A process for infusing resin into a fibrous reinforcement, comprising: infusing a curable flowing fluid resin composition into a fibrous reinforcement material, wherein the curable flowing fluid resin composition comprises a resin component and an activator component, and at least one property of the curable flowing fluid resin composition is monitored prior to infusion.

2. The resin infusion process according to claim 1, further comprising: a feedback loop whereby the monitoring is used to control the composition of the curable flowing fluid resin composition.

3. (canceled)

4. (canceled)

5. (canceled)

6. (canceled)

7. The resin infusion process according to claim 2, in which the curable flowing fluid composition and/or the resin component is liquid.

8. The resin infusion process according to claim 7, in which the property that is monitored is the viscosity of the curable flowing fluid resin composition.

9. The resin infusion process according to claim 7, in which the property that is monitored is the T.sub.g of the curable flowing fluid resin composition.

10. The resin infusion process according to claim 7, wherein at least one property of the curable flowing fluid resin composition is monitored at regular time intervals.

11. The resin infusion process according to claim 7, wherein the activator component of the curable flowing fluid resin composition is an amine based reactive compound and the resin component of the curable flowing fluid resin composition comprises an epoxy resin component.

12. The resin infusion process according to claim 11, wherein the ratio of amine to epoxy groups in the curable flowing fluid resin composition is monitored.

13. (canceled)

14. The resin infusion process according to claim 12, in which the property that is monitored is the chemical composition or stoichiometry of the curable flowing fluid resin composition.

15. The resin infusion process according to claim 14, wherein the chemical composition or stoichiometry of the curable flowing fluid resin composition is monitored by a near infrared spectrometer.

16. (canceled)

17. The resin infusion process according to claim 15, wherein the spectrometer is an FTIR or FT-NIR spectrometer.

18. The resin infusion process according to claim 17, wherein the chemical composition or stoichiometry of the curable flowing fluid resin composition is monitored as the curable flowing fluid resin composition passes through a measurement component.

19. The resin infusion process according to claim 18, wherein the measurement component comprises a conduit.

20. The resin infusion process according to claim 19, wherein the spectrometer is located outside the measurement component so that the curable flowing fluid resin composition does not contact any part of the spectrometer.

21. The resin infusion process according to claim 20, wherein the walls of the measurement component do not absorb in the regions used for the spectroscopic monitoring.

22. The resin infusion process according to claim 21, wherein the measurement component is at least partially formed from silicone, a perfluoroalkoxy material or glass.

23. The resin infusion process according to claim 22, wherein the internal diameter of the measurement component is selected to not interfere with the spectroscopic monitoring.

Description

[0036] The invention is illustrated but in no way limited to the accompanying drawings in which.

[0037] FIG. 1 is a schematic illustration of the process of this invention;

[0038] FIG. 2 is the schematic illustration according to FIG. 1 including a feedback loop for the adjustment of the resin composition;

[0039] FIG. 3 is an infrared plot according to Example 1;

[0040] FIG. 4 is a diagram showing the ratio of epoxy groups in relation to amine groups in a resin composition over time;

[0041] FIG. 5 is a diagram showing the percentage curative measured in a standard batch of curable resin over three test runs in accordance with Example 2; and

[0042] FIG. 6 is a diagram showing the percentage curative measured in two non-standard batches of curable resin in accordance with Example 3.

[0043] FIG. 1 shows three sources of components (1, 2 and 3) comprising a resin (1) an activator (2) and an accelerator (3) for the activator. The components are fed to a mixer (4) where they are mixed and pumped to a mould (5). A spectrometer (6) is provided to monitor the composition of the fluid resin being supplied to the mould.

[0044] In FIG. 2 the same numerals indicate the same components as in FIG. 1, with the addition of a feedback loop (7), which can adjust the feed of the components (1, 2 and 3) as required as indicated by the monitoring by the spectrometer.

[0045] The invention is further illustrated by the following Examples.

EXAMPLE 1

[0046] A fibre optic probe is introduced between the outlet of a two-component resin component mixing machine and the inlet of a mould as shown in FIG. 1. The machine is adapted to produce an infusion resin composition from multiple components. The mould may be for the production of an aerospace component.

[0047] The mixing machine was an Isojet two-component mixing machine and was used to mix a resin composition comprising component A, which is a mixture of epoxy resins and component B, which is a mixture of amine based activator components also commonly referred to as curatives.

[0048] The probe transfers a signal to an infra-red analyser that produces spectra that can be interpreted in real-time to give a measure of the composition of the resin mixture such as the amine to epoxy concentration ratio. The spectra may also be analysed to check for impurities or other chemical species.

[0049] The output of the infra-red analyser could be set as an alarm or to stop the mixing or injection processes if the mixture is not within predefined tolerances.

[0050] The mixing machine consists of two heated tanks for storing Part A and Part B components. An arrangement of gear pumps and flow meters feeds the two components to a static mixer in the desired ratio. As the components flow through the mix-head intimate mixing occurs and the resin composition is then ready for supply to a mould for infusion with fibre to produce a composite part. An ATR (attenuated total reflectance) probe was inserted into the path of the flowing resin after the static mixer and the signal from the probe transferred to a Fourrier transform infrared (FTIR) analyser by a fibre optic. The analyser and software record and interpret the spectra to give a ratio of amine to epoxy content of the mixture which can be determined from the relative area under the FTIR peaks associated with epoxide and amine function groups. The nominal correct ratio of epoxy to amine was selected to be 100 parts resin to 68.1 parts of amine. For simplicity the mix ratio is defined as the parts amine per 100 epoxy, in this case 68.1 by weight or 79.5 by volume.

[0051] The infrared spectral plot of such a mixture is shown in FIG. 3.

[0052] In order to illustrate the invention the ratio of amine to epoxy based components in the resin composition was varied, and the plot of mix ratio (% change from nominal of 68.1) calculated by the FTIR software, showing the change from nominal ratio as the resin composition is mixed at different ratios of the components, is shown in FIG. 4.

[0053] To maintain robust performance of the invention, it is necessary to maintain the mix ratio with 3% of nominal. These data show that the in-line FTIR probe and analyser can accurately track changes to 1% of nominal.

EXAMPLE 2

[0054] A calibration model was built by carrying out NIR spectroscopic analysis of a curable epoxy resin based system containing various known concentrations of amine curative. The epoxy resin was based on HexFlow RTM6, available from Hexcel Corporation, USA, but with the concentration of the curative altered by a known amount in some cases. The testing was carried out by passing the resin compositions through a 12 mm diameter glass tube that was 100 or 130 mm in length, with a wall thickness of 2.2 mm. The glass tube was then inserted into a suitable holder and then attached to a Clippir wet process analyser accessory (ACC127, available from ABB, USA) comprising an FT-NIR spectrometer probe. The spectrometer probe was connected to an FT-NIR single channel process analyser (TALYS ASP501, available from ABB, USA).

[0055] Once the calibration model had been built a batch of HexFlow RTM6 resin having a standard (nominal) concentration of curative was tested in 3 runs for up to 800 seconds. The measured deviation in the concentration of the curative compared to the nominal value in each run is shown in FIG. 5.

[0056] As shown in FIG. 5, the test method according to the present invention was able to measure the concentration of the curative with an accuracy of no more than plus or minus 0.5% of the actual value.

EXAMPLE 3

[0057] The method of Example 2 was repeated using resins that were not used to construct the model in Example 2. A first batch of HexFlow RTM6 having an adjusted concentration of curative of plus 2% of the normal value, and a second batch having an adjusted concentration of curative of minus 2% of the normal value were tested, as set out in Example 2. The results are shown in FIG. 6.

[0058] As shown in FIG. 6, the test method according to the present invention was able to accurately detect changes in the curative concentration of plus or minus 2% of the nominal concentration.