Method for optimizing the mass of a composite panel

1. A process for making a composite panel, said panel being composed of a plurality of uniform thickness zones, each uniform thickness zone being defined by a vertical arrangement of plies having different orientation angles, said arrangement being defined by a determined number of plies, a positioning order of the plies having a given orientation angle with respect to the others in the vertical arrangement, and the proportion of plies having a given orientation angle with respect to all the plies composing the vertical arrangement, said process comprising:

a first step of defining a lay-up table describing an optimal arrangement of plies taking into account mass constraints as well as structural constraints imposed to the panel;

a second stage comprising producing the panel, including arranging the panel to include different plies with different orientation angles in accordance with the optimal arrangement described in the table lay-up, so as to realize said plurality of zones of uniform thickness;

the first step further comprising the steps of:

defining a lay-up table, said table defining a vertical arrangement of the plies for each uniform thickness zone;

starting from said lay-up table, building a function describing the physical properties of each zone of the composite panel as a function of the total thickness of each zone;

adjusting the total thickness for each zone using a discrete variables iteration process, to minimize the mass of the panel,

said adjustment of the total thickness for each uniform thickness zone resulting in a modification of the number of plies for each of said uniform thickness zones using the corresponding lay-up table.

2. The process according to claim 1 , wherein defining the lay-up table includes building the table by determining idealistic proportions of plies having a given orientation angle with respect to the total thickness for each uniform thickness zone of the panel using a discrete variables iteration process, so as to minimize the total mass of the panel.

3. The process according to claim 2 , further comprising upon completion of building the table:

defining a function giving the proportion of plies having a given orientation angle as a function of the total thickness for each uniform thickness zone; and

determining the optimum total thickness using a discrete variables iteration process, so as to minimize the total mass of the panel.

4. The process according to claim 3 , wherein the derivative of the said function is positive so as to impart ply continuity between two adjacent uniform thickness zones.

5. The process according to claim 1 , comprising, prior to building a function describing the physical properties of each zone of the composite panel:

adjusting the positioning order of the plies having a given orientation angle different from the others in the arrangement for each uniform thickness zone using a discrete variables iteration process, the aim of the process being reached when the buckling resistance corresponds to a predefined threshold value.

6. The process according to claim 1 , the lay-up table is a pre-existing lay-up table for building the function describing the physical properties of each zone of the composite panel.

7. The process according to claim 1 , wherein upon completion of building a function describing the physical properties of each zone of the composite panel, determining the exact number of plies for each uniform thickness zone of the panel using a discrete variables iteration process, the aim of the process being reached when the mass of the panel is minimum.

8. The process according to claim 1 , wherein all the plies composing the vertical arrangement have the same thickness.

9. The process according to claim 1 , wherein the said composite panel is a plane or curved panel.

10. The process according to claim 1 , wherein the plies are unidirectional pre-impregnated plies.

11. The process according to claim 1 , wherein the plies are woven plies.