This application claims the benefit of the European patent application No. 13382509.1 filed on Dec. 13, 2013, the entire disclosures of which are incorporated herein by way of reference.
This invention relates to methods of manufacturing partially cured composite components and also to methods of manufacturing composite structures using partially cured composite components.
Composites are made up from individual laminas bonded together at a certain temperature in a single consolidated laminate. Each layer is composed of a mixture of fibers and resin. The resin flows within and between the laminas before getting to its curing temperature.
Composite laminates are used extensively in the aeronautical industry as well as in other industries.
In conventional manufacturing processes, the components of a composite structure are manufactured independently and subsequently joined or assembled to reach the final structure.
Three types of techniques are available to get a final composite structure without using rivets as joining elements of its components: co-curing un-cured components, co-bonding cured components with un-cured components and bonding cured components between them (secondary bonding).
The co-curing technique is the best from a structural point of view but requires a complicate tooling for handling the assembly of un-cured components.
A known approach to solve this problem is using partially cured composite components because they can be better handled than fully un-cured components. In a known method to produce panels with two curing areas a composite layup is placed in a two chamber mold between four semi-rigid membranes and then, while vacuum is applied to the layup, temperature and pressure is exerted to the layup by fluids introduced into the chambers (see www.quickstep.com.au/ for further information).
A disadvantage of that method for, particularly, manufacturing partially cured large composite components is the complexity and cost of the tooling required.
The present invention is directed to the solution of said drawback.
An object of the present invention is to provide an efficient method for manufacturing a partially cured composite component intended to be joined with other component or components to form a composite structure.
Another object of the present invention is to provide a method for manufacturing a composite structure with partially cured components manufactured by the above method.
The method of manufacturing a partially cured composite component according to the invention comprises:
A suitable combination of heat conductive and insulating elements taking into account the geometry of the composite component being manufactured and the desired curing degree of different portions of the same allows the application of a predetermined cycle of pressure and heat to the mold to achieve the desired result. In particular, the dimension of the transition portions between the cured and un-cured portions can be properly controlled.
Advantageously, the heat conductive and insulating elements are rigid elements. This facilitates the preparation of the mold and the control of the transmission of heat to the different portions of the composite layup.
Advantageously, pressure is applied on two opposite faces of the mold by mechanical pressure elements such as pressure plates. The aforementioned mold structure allows configuring the mold with two opposite faces adapted to the shape of the pressure elements being used.
Advantageously, heat is applied to the mold in one direction, for example by applying it on one side of the mold. This simplifies the tooling required. Depending on the component being manufactured, heat can be applied to the whole mold or only to an element of the mold.
The method of manufacturing a composite structure according to the invention comprises:
This method is particularly applicable for the manufacture of, for example, skins of aircraft lifting surfaces reinforced with T-shaped or omega-shaped stringers, being the first layup the skin layup, the second layups the stringer layups and the un-cured portions of the stringers their feet and a portion of their webs.
Other characteristics and advantages of the present invention will be clear from the following detailed description of embodiments illustrative of its object in relation to the attached figures.
In relation to the curing degree of a portion of a composite component, in this specification an un-cured portion shall be understood as a portion with a curing degree lower than 20%, a cured portion as a portion with a curing degree higher than 80% and a partially cured portion as a portion with a curing degree between 20-80%.
In reference to
In a first step, a composite layup 11 is disposed in a mold formed by steel boxes 21 and mica plates 23.
In a second step, heat and pressure are applied on the mold using a heated upper pressure plate 13 and a lower pressure plate 15.
Steel boxes 21, used as heat conductive elements, and mica plates 23, used as heat insulating elements, are arranged so that the heat comes from the heated upper pressure plate 13 to the central portion of the layup 11 through the upper steel box 21 as shown by the straight arrows of
This arrangement allows controlling the application of heat to the layup 11 so that its central portion, disposed between the upper steel box 21 and the lower mica plate 23, is cured and the side portions, disposed between the upper mica plates 23 and the lower steel boxes 21, remain un-cured except in some portions close to the central portion where they are partially cured.
In reference to
In a first step, a T-shaped composite layup 11 is disposed in a mold formed by steel boxes 21 and mica plates 23 with the web in the lower part and the foot in the upper part.
In a second step, heat and pressure are applied on the mold using the heated lower pressure plate 13 and the upper pressure plate 15.
Steel boxes 21, used as heat conductive elements, and mica plates 23, used as heat insulating elements, are arranged so that the heat comes from the heated lower pressure plate 13 to a first portion of the web of the layup 11 through the lower steel boxes 21, as indicated by the straight arrows in
In reference to
In a first step, an omega-shaped composite layup 11 is disposed in a mold formed by a steel box 22, equipped with heating elements for acting as a self-heated module, steel boxes 21, used as heat conductive elements, and mica plates 23, used as heat insulating elements.
In a second step, pressure is applied on the mold by means of two pressure plates 15 and the self-heated module 22 is activated for the application of heat.
The self-heated module 22 and the mica plates 23 are arranged so that heat reaches the head of the omega-shaped layup 11 as indicated by the straight arrows in
Method of manufacturing of a structure with composite components partially cured
In an embodiment to manufacture, for example, a skin reinforced with T-shaped stringers of an aircraft lifting surface, the method of the invention comprises:
Although the present invention has been described in connection with various embodiments, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made, and are within the scope of the invention.
Number | Date | Country | Kind |
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13382509.1 | Dec 2013 | EP | regional |