Fiber-reinforced, composite, structural member exhibiting non-linear strain-to-failure and method of making same

1. A fiber-reinforced, organic matrix, composite structural member, comprising:

a plurality of layers of fiber-reinforced, organic matrix, composite material in which adjacent layers are bonded to one another, the plurality of layers having:

a first, innermost layer comprising reinforcing fibers oriented generally at 90 degrees with respect to a loading direction of the structural member;

a second layer disposed on the first layer, the second layer comprising reinforcing fibers oriented generally at ±25 degrees with respect to the loading direction of the structural member;

a third layer disposed on the second layer, the third layer comprising reinforcing fibers oriented generally at 90 degrees with respect to the loading direction of the structural member;

a fourth layer disposed on the third layer, the fourth layer comprising reinforcing fibers oriented generally at ±30 degrees with respect to the loading direction of the structural member;

a fifth layer disposed on the fourth layer, the fifth layer comprising reinforcing fibers oriented generally at 90 degrees with respect to the loading direction of the structural member; and

a sixth layer disposed on the fifth layer, the sixth layer comprising reinforcing fibers oriented generally at ±45 degrees with respect to the loading direction of the structural member;

wherein the structural member is configured to exhibit a non-linear stress-strain response when mechanically loaded to failure.

2. The structural member, according to claim 1 , wherein the fiber-reinforced, organic matrix, composite material comprises:

a plurality of one or more of carbon, graphite, glass, and aramid fibers.

3. The structural member, according to claim 1 , wherein the fiber-reinforced, organic matrix, composite material comprises:

a thermoplastic or thermosetting polymeric matrix.

4. The structural member, according to claim 3 , wherein the thermoplastic or thermosetting polymeric matrix comprises:

a poly-ether-ketone-ketone material.

5. The structural member, according to claim 1 , wherein the fiber reinforced, organic matrix, composite material comprises a plurality of reinforcing fibers and substantially all of the plurality of reinforcing fibers are misaligned with a loading direction of the structural member.

6. The structural member, according to claim 1 , wherein the plurality of layers comprises:

a plurality of layers comprising reinforcing fibers; and

a layer disposed between the plurality of layers comprising reinforcing fibers oriented generally at 90 degrees to a loading direction of the structural member.

7. The structural member, according to claim 1 , wherein the structural member has a tubular form.

8. A helicopter landing gear, comprising:

a pair of skids; and

one or more cross members extending between the pair of skids, the one or more cross members comprising:

a plurality of layers of fiber-reinforced, organic matrix, composite material in which adjacent layers are bonded to one another, the plurality of layers having:

a first, innermost layer comprising reinforcing fibers oriented generally at 90 degrees with respect to a loading direction of the structural member;

a second layer disposed on the first layer, the second layer comprising reinforcing fibers oriented generally at ±25 degrees with respect to the loading direction of the structural member;

a third layer disposed on the second layer, the third layer comprising reinforcing fibers oriented generally at 90 degrees with respect to the loading direction of the structural member;

a fourth layer disposed on the third layer, the fourth layer comprising reinforcing fibers oriented generally at ±30 degrees with respect to the loading direction of the structural member;

a fifth layer disposed on the fourth layer, the fifth layer comprising reinforcing fibers oriented generally at 90 degrees with respect to the loading direction of the structural member; and

a sixth layer disposed on the fifth layer, the sixth layer comprising reinforcing fibers oriented generally at ±45 degrees with respect to the loading direction of the structural member;

wherein the one or more cross members are configured to exhibit non-linear stress-strain responses when mechanically loaded to failure.

9. The helicopter landing gear, according to claim 8 , wherein the fiber-reinforced, organic matrix, composite material comprises:

a plurality of one or more of carbon, graphite, glass, and aramid fibers.

10. The helicopter landing gear, according to claim 8 , wherein the fiber-reinforced, organic matrix, composite material comprises:

a thermoplastic or thermosetting polymeric matrix.

11. The helicopter landing gear, according to claim 10 , wherein the thermoplastic or thermosetting polymeric matrix comprises:

a poly-ether-ketone-ketone material.

12. The helicopter landing gear, according to claim 8 , wherein the fiber reinforced, organic matrix, composite material comprises a plurality of reinforcing fibers and substantially all of the plurality of reinforcing fibers are misaligned with loading directions of the one or more cross members.

13. The helicopter landing gear, according to claim 8 , wherein the plurality of layers comprises:

a plurality of layers comprising reinforcing fibers; and

a layer disposed between the plurality of layers comprising reinforcing fibers oriented generally at 90 degrees to loading directions of the one or more cross members.

14. The helicopter landing gear, according to claim 8 , wherein the one or more cross members have tubular forms.