Pre-strained composite test coupons
First Claim
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1. 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;
inner ply layers having first fibers and a first matrix material associated with the first fibers, the first fibers oriented in a first direction; and
outer ply layers having second fibers and a second matrix material associated with the second fibers, the outer ply layers including outermost ply layers and 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 of the first fibers;
removing the first tensile load after the first tensile load causes cracking along the second direction and between the second fibers of each of the outermost ply layers;
after removing the first tensile load, 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 of the first fibers;
receiving, from the testing device, strain values of the test coupon during tensile loading of the test coupon; and
determining one or more modulus values associated with a first contribution corresponding to the inner ply layers based on the strain values and based on a nominal thickness of a ply area associated with the inner ply layers, the first contribution independent of a second contribution of the outer ply layers.
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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.
29 Citations
18 Claims
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1. A method comprising:
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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; inner ply layers having first fibers and a first matrix material associated with the first fibers, the first fibers oriented in a first direction; and outer ply layers having second fibers and a second matrix material associated with the second fibers, the outer ply layers including outermost ply layers and 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 of the first fibers; removing the first tensile load after the first tensile load causes cracking along the second direction and between the second fibers of each of the outermost ply layers; after removing the first tensile load, 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 of the first fibers; receiving, from the testing device, strain values of the test coupon during tensile loading of the test coupon; and determining one or more modulus values associated with a first contribution corresponding to the inner ply layers based on the strain values and based on a nominal thickness of a ply area associated with the inner ply layers, the first contribution independent of a second contribution of the outer ply layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A system comprising:
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a processor; and 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; inner ply layers having first fibers and a first matrix material associated with the first fibers, the first fibers oriented in a first direction; and outer ply layers having second fibers and a second matrix material associated with the second fibers, the outer ply layers including outermost ply layers and 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 of the first fibers; removing the first tensile load after the first tensile load causes cracking along the second direction and between the second fibers of each of the outermost ply layers, the removing including causing a magnitude of the first tensile load to be zero; after removing the first tensile load, 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 of the first fibers; 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 a first contribution corresponding to the inner ply layers based on the strain values and based on a nominal thickness of a ply area associated with the inner ply layers, the first contribution independent of a second contribution associated with the outer ply layers. - View Dependent Claims (15, 16, 17)
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18. A system comprising:
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a processor; and 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; inner ply layers having first fibers and a first matrix material associated with the first fibers, the first fibers oriented in a first direction; and outer ply layers having second fibers and a second matrix material associated with the second fibers, the outer ply layers including outermost ply layers and 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 of the first fibers; removing the first tensile load after the first tensile load causes cracking along the second direction and between the second fibers of each of the outermost ply layers, the removing including causing a magnitude of the first tensile load to be zero; after removing the first tensile load, 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 of the first fibers; and calculating one or more tensile strength values associated with a first contribution corresponding to the inner ply layers based on a nominal thickness of a ply area associated with the inner ply layers, the first contribution independent of a second contribution associated with the outer ply layers.
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Specification