Stock material or miscellaneous articles – Structurally defined web or sheet – Honeycomb-like
Patent
1996-03-22
1999-01-05
Smith, Jeffrey T.
Stock material or miscellaneous articles
Structurally defined web or sheet
Honeycomb-like
264257, 264261, 2642711, 2642791, 428116, B32B 312
Patent
active
058559841
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a composite article and a method of moulding composite articles from fibre reinforced synthetic curable resins.
The composite access covers described in our European patent number 0147050 have an internal structure which is very efficient and leads to high load bearing qualities for the weight of material used. The design of this structure is based on the concept of employing two plates which are separated by webs. A structure of this type provides a high value of second moment of area, in relation to the quantity of material used, and the greater this value the stiffer the structure will be and the greater its load bearing capacity. Within the structure the reinforcing fibres are arranged in an optimised manner. That is, the fibres are arranged so as to correspond with the direction of the anticipated stresses which will occur within the structure when subjected to load.
Our European patent numbers 0365579 and 0408639 describe methods which enable the complex three dimensional structure of these access covers to be injected with a matrix resin in a very effective and speedy manner even when high fibre volume fractions are employed. In order to obtain the necessary strength to weight ratio in load bearing composite articles of this type, it is necessary to employ very high fibre volume fractions. The access covers referred to above have fibre volume fractions ranging from 43-50%. Normally such high fibre volume fractions are very difficult to inject in commercially acceptable moulding times, which limited the size of composite article which could be moulded prior to the process of our above mentioned European patents.
Access covers and other load bearing composite articles made as described above are excellent high load bearing structures capable of competing with the hitherto used alternatives fabricated from metal. However, when the load requirements are less severe, for example an access cover for pedestrian areas, it is desirable to reduce the cost of production. A significant proportion of the expense in the structures referred to above is contributed by the polyurethane foam cores used to create the three dimensional structure. It would therefore be an advantage, in respect of medium duty structures, to eliminate the polyurethane cores while still retaining the structural benefits of a high fibre volume fraction.
The invention seeks to provide a composite article, and method of making the same, improved in the above respects.
According to the present invention there is provided a method of moulding a composite article by injecting a plastics material resin into fibres within a mould characterised in that a continuous web of fibres is laid in a mould in such a fashion that a honeycomb structure is produced without the web crossing itself.
The term "honeycomb" is used herein to refer to spaces being enclosed by the web where it touches itself but should not be construed as being limited to such spaces being hexagonal or even being regular in nature.
The invention extends to a composite article produced by the method described above.
In a preferred form of the method of the invention the honeycomb is laminated to a plate during moulding by providing a flat sheet of fibres contiguous with the honeycomb structure and injecting the whole simultaneously. If desired, a honeycomb structure can be provided on either side of the plate. Alternatively, if required, a plate may be provided on either side of the honeycomb structure but in this case it is necessary to use foam inserts to prevent seepage of the resin into the interstices of the honeycomb and in this case the cost advantage over the structure described in European patent number 0 147 050 is not as great. Nevertheless there are certain circumstances in which such a structure is desirable and it remains within the ambit of the present invention.
The fibrous web forming the honeycomb is, as referred to above, preferably continuous throughout the article being moulded. Discontinuities in the web lead to weak spots in the moulded
REFERENCES:
patent: 4090002 (1978-05-01), Rosenblum
3-D Composites Limited
Aylward D.
Smith Jeffrey T.
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