PRE-STRAINED COMPOSITE TEST COUPONS

• US 20160349160A1
• Filed: 06/01/2015
• Published: 12/01/2016
• Est. Priority Date: 06/01/2015
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Tucker, Samuel J., Esposito, Jack J.
• Granted Patent: US 10,190,954 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B29C 66/721 Fibre-reinforced materials B29C66/729 takes precedence
• CPC Class Codes: B29C 66/7212 characterised by the composition of the fibres
• CPC Class Codes: B29C 70/202 arranged in parallel planes or structures of fibres crossing at substantial angles, e.g. cross-moulding compound [XMC] B29C70/207 takes precedence
• CPC Class Codes: B29C 70/207 arranged in parallel planes of fibres crossing at substantial angles
• CPC Class Codes: B29C 70/228 the structure being stacked in parallel layers with fibres of adjacent layers crossing at substantial angles
• CPC Class Codes: G01N 2203/0017 Tensile
• CPC Class Codes: G01N 2203/006 Crack, flaws, fracture or rupture
• CPC Class Codes: G01N 2203/0062 Crack or flaws
• CPC Class Codes: G01N 2203/0073 Fatigue
• CPC Class Codes: G01N 2203/0075 Strain-stress relations or elastic constants
• CPC Class Codes: G01N 2203/0091 Peeling or tearing
• CPC Class Codes: G01N 2203/0096 Fibre-matrix interaction in composites
• CPC Class Codes: G01N 2203/0208 Specific programs of loading, e.g. incremental loading or pre-loading
• CPC Class Codes: G01N 2203/0252 Monoaxial, i.e. the forces being applied along a single axis of the specimen
• CPC Class Codes: G01N 2203/028 One dimensional, e.g. filaments, wires, ropes or cables
• CPC Class Codes: G01N 2203/0282 Two dimensional, e.g. tapes, webs, sheets, strips, disks or membranes
• CPC Class Codes: G01N 2203/0298 Manufacturing or preparing specimens
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 3/08 by applying steady tensile or compressive forces G01N3/28 takes precedence
• CPC Class Codes: G01N 3/18 : Performing tests at high or low temperatures

Abstract

A composite test coupon includes a plurality of plies. The plurality of plies include first ply layers and second ply layers. The first ply layers have first fibers and a substantially uniform matrix material associated with the first fibers. The second ply layers have second fibers and a pre-stressed matrix material associated with the second fibers. The first fibers are oriented in a first direction, and the second fibers are oriented in a second direction that is different from the first direction. The pre-stressed matrix material includes stress induced cracks between the second fibers of each of the second ply layers.

Claims

1. A composite test coupon comprising:

a plurality of plies including;

first ply layers having first fibers and a substantially uniform matrix material associated with the first fibers, the first fibers oriented in a first direction; and

second ply layers having second fibers and a pre-stressed matrix material associated with the second fibers, the second fibers oriented in a second direction that is different from the first direction, wherein the pre-stressed matrix material includes stress induced cracks between the second fibers of each of the second ply layers.

2. The composite test coupon of claim 1, wherein the plurality of plies includes:

a first set of plies associated with the first ply layers, the first set of plies including a first number of plies; and

a second set of plies associated with the second ply layers, the second set of plies including a second number of plies.

3. The composite test coupon of claim 2, wherein the first number of plies is the same as the second number of plies.

4. The composite test coupon of claim 2, wherein the first number of plies includes at least two plies, and wherein the second number of plies includes at least two plies.

5. The composite test coupon of claim 4, wherein the first number of plies includes four plies, and wherein the second number of plies includes four plies.

6. The composite test coupon of claim 2, wherein an arrangement of the plurality of plies includes:

a first ply of the second set of plies;

a second ply of the first set of plies, the second ply disposed adjacent to the first ply;

a third ply of the first set of plies, the third ply disposed adjacent to the second ply; and

a fourth ply of the second set of plies, the fourth ply disposed adjacent to the third ply.

7. The composite test coupon of claim 2, wherein an arrangement of the plurality of plies includes:

a first ply of the second set of plies;

a second ply of the first set of plies, the second ply disposed adjacent to the first ply;

a third ply of the second set of plies, the third ply disposed adjacent to the second ply;

a fourth ply of the first set of plies, the fourth ply disposed adjacent to the third ply;

a fifth ply of the first set of plies, the fifth ply disposed adjacent to the fourth ply;

a sixth ply of the second set of plies, the sixth ply disposed adjacent to the fifth ply;

a seventh ply of the first set of plies, the seventh ply disposed adjacent to the sixth ply; and

an eighth ply of the second set of plies, the eighth ply disposed adjacent to the seventh ply.

8. The composite test coupon of claim 1, wherein the first ply layers and the second ply layers have substantially similar material compositions.

9. A method comprising:

inserting a test coupon of a composite material having a plurality of layers into a testing device that has a first element to secure the test coupon and a second element to secure the test coupon, wherein the plurality of layers of the test coupon are arranged in a cross-ply layup including;

first ply layers having first fibers and a first matrix material associated with the first fibers, the first fibers oriented in a first direction; and

second ply layers having second fibers and a second matrix material associated with the second fibers, the second fibers oriented in a second direction that is different than the first direction;

performing a first loading operation on the test coupon, wherein the first loading operation includes applying a first tensile load oriented in the first direction, the first tensile load corresponding to a threshold load that is less than a failure load; and

after performing the first loading operation, performing a second loading operation on the test coupon, wherein the second loading operation includes increasing tensile loading of the test coupon to the failure load.

10. The method of claim 9, further comprising measuring strain values of the test coupon during tensile loading of the test coupon to the failure load.

11. The method of claim 10, further comprising calculating one or more modulus values associated with the first ply layers based on the measured strain values.

12. The method of claim 9, wherein the test coupon does not include adhesive tabs for securing the test coupon to the first element and the second element of the testing device.

13. The method of claim 9, wherein the first loading operation and the second loading operation are performed above a temperature threshold, above a humidity threshold, or a combination thereof.

14. The method of claim 9, further comprising, prior to performing the first loading operation, using the testing device to determine the failure load using a sacrificial test coupon that is substantially similar to the test coupon.

15. The method of claim 9, wherein the threshold load is in a range of about 85 percent to about 99 percent of the failure load.

16. The method of claim 9, wherein the first element of the testing device includes a first friction pad to secure a first end of the test coupon, and wherein the second element of the testing device includes a second friction pad to secure a second end of the test coupon.

17. A system comprising:

a processor;

a memory in communication with the processor, the memory including instructions executable by the processor to perform operations including;

communicating with a testing device that is configured to perform load testing operations on a test coupon of a composite material having a plurality of layers, wherein the plurality of layers of the test coupon are arranged in a cross-ply layup including;

first ply layers having first fibers and a first matrix material associated with the first fibers, the first fibers oriented in a first direction; and

second ply layers having second fibers and a second matrix material associated with the second fibers, the second fibers oriented in a second direction that is different than the first direction;

sending a first set of instructions to the testing device to perform a first loading operation on the test coupon, wherein the first loading operation includes applying a first tensile load oriented in the first direction, the first tensile load corresponding to a threshold load that is less than a failure load; and

sending a second set of instructions to the testing device to perform a second loading operation on the test coupon, wherein the second loading operation includes increasing tensile loading of the test coupon to the failure load.

18. The system of claim 17, wherein the operations further include:

receiving, from the testing device, strain values of the test coupon during tensile loading of the test coupon to the failure load; and

calculating one or more modulus values associated with the first ply layers based on the measured strain values.

19. The system of claim 18, wherein the one or more modulus values are determined based on nominal thickness values associated with the first ply layers of the plurality of layers of the test coupon.

20. The system of claim 17, wherein the operations further include:

prior to performing the first loading operation, sending a third set of instructions to the testing device to perform a failure load testing operation on a sacrificial test coupon that is substantially similar to the test coupon; and

calculating the threshold load based on information received from the testing device that is associated with the failure load testing operation on the sacrificial test coupon.