Method for making a structural part of a composite material having a calibrated thickness and structural part thus obtained
View Patent ↗The disclosed embodiments offer a solution for controlling the thickness of a finished structural composite part when precise tolerances must be complied with for the quality of the assembly and in order to ease the assembly operations of this part. In order to implement the method according to the disclosed embodiments, an additional layer of plies made out of a non-structural composite material, called calibrating plies, is applied onto the structural plies of the structural part, at least in an area where the thickness must be maintained within close tolerances and, after the composite material has been cured, the calibrating plies are machined in order to obtain the thickness required for the finished part. The thickness of the calibrating plies applied is determined according to the possible thicknesses of structural plies, taking into account the manufacturing spreads so that the machining operation for the calibrating plies does not affect the structural plies.
1. A method for producing a structural part from structural plies comprising fibres in a cured resin, said structural plies being capable of resisting strain, the method compromising:
determining a minimum structural thickness value and a maximum structural thickness value for a predetermined thickness area of the structural part;
determining a normal thickness value Enom for the predetermined thickness area of the structural part, wherein the normal thickness value is greater than the maximum structural thickness value;
applying the structural plies to achieve, upon curing the resin, a structural thickness Es for the structural part, wherein the structural thickness Es is between the minimum structural thickness value and the maximum structural thickness values;
applying one or more non-structural calibrating plies, not required for strain resistance, to at least one side of the structural plies to achieve a thickness ΔE of the one or more non-structural calibrating plies at least equal to the nominal thickness value Enom for the predetermined thickness area of the structural part minus the minimum structural thickness value;
connecting the structural plies and non-structural calibrating plies; and
calibrating a cured thickness of the structural part by machining the non-structural calibrating plies so that the cured thickness of said structural part in the predetermined thickness area is within upper and lower tolerances for the nominal thickness value Enom.
2. A method according to claim 1 , wherein the minimum structural thickness value is determined from a minimum thickness of each of the structural plies.
3. A method according to claim 1 , wherein the maximum structural thickness value is determined from a maximum thickness of each of the structural plies.
4. A method according to claim 1 , wherein the non-structural calibrating plies are produced with a composite material including fibres in a resin compatible with the resin of structural composite material.
5. A method according to claim 1 , wherein the resin of the structural plies is chosen from the resins cured by polymerisation.
6. A method according to claim 1 , wherein at least one non-structural calibrating ply is applied on each of the sides of structural plies in at least the predetermined thickness area.
7. A method according to claim 1 , wherein at least one visual ply is applied between the structural plies on the non-structural calibrating plies, or between the non-structural calibrating plies, said visual ply comprising characteristics visually distinguishing the at least one visual ply from the non-structural calibrating plies and from the structural plies upon machining the non-structural calibrating plies.