So - what is the best way to measure strain on a composite material?! Clip-on extensometer? Strain gage?? Optical extensometry??
There are some pretty strong forces that dictate the choice of extensometry for tensile tests on composites: standards (many call for strain gages), history (your company data files and history), new technology (non-contacting, video, optical), and PAIN - just how painful is your current process and what is the payback associated with changing to something new.
One of the main challenges of marketing testing technology into the Composites world is balancing all these competing forces - especially when something new comes along, like the Instron AVE: Advanced Video Extensometer. On paper, the AVE has an accuracy of about 2.5 microns, theoretically insufficient for measuring the modulus of stiff composite materials. BUT, is it "good enough"?
We have done a lot of testing with carbon-fiber reinforced laminate (and tow) materials and found that the AVE provides very promising modulus results, that are consistent with historical data. The good news is that the AVE could potentially eliminate the need to apply strain gages to many QC samples - saving time, money, and hassle. We are currently investigating the possibility of using the AVE for fiber-reinforced materials and things look good so far. The challenge remains for dealing with existing standards, procedures, and customer expectations - but we are committed to the cause and will see how this effort pans out! If you (the reader) are testing composites and are interested in alternative methods for measuring strain, please be sure to contact us. The best way to determine if the AVE is suitable for your composite materials and applications is to run tests in our Applications Laboratory.
I will be sure to post links to applications reports that compare the output of tensile tests that were run on laminates with strain gage, clip-on, and AVE all at the same time - as soon as we clean it up for public consumption!
Comments and feedback welcome!
There are some pretty strong forces that dictate the choice of extensometry for tensile tests on composites: standards (many call for strain gages), history (your company data files and history), new technology (non-contacting, video, optical), and PAIN - just how painful is your current process and what is the payback associated with changing to something new.
One of the main challenges of marketing testing technology into the Composites world is balancing all these competing forces - especially when something new comes along, like the Instron AVE: Advanced Video Extensometer. On paper, the AVE has an accuracy of about 2.5 microns, theoretically insufficient for measuring the modulus of stiff composite materials. BUT, is it "good enough"?
We have done a lot of testing with carbon-fiber reinforced laminate (and tow) materials and found that the AVE provides very promising modulus results, that are consistent with historical data. The good news is that the AVE could potentially eliminate the need to apply strain gages to many QC samples - saving time, money, and hassle. We are currently investigating the possibility of using the AVE for fiber-reinforced materials and things look good so far. The challenge remains for dealing with existing standards, procedures, and customer expectations - but we are committed to the cause and will see how this effort pans out! If you (the reader) are testing composites and are interested in alternative methods for measuring strain, please be sure to contact us. The best way to determine if the AVE is suitable for your composite materials and applications is to run tests in our Applications Laboratory.
I will be sure to post links to applications reports that compare the output of tensile tests that were run on laminates with strain gage, clip-on, and AVE all at the same time - as soon as we clean it up for public consumption!
Comments and feedback welcome!
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