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Wave speed propagation measurements on highly attenuative heated materials

Physics Procedia

Moore, David G.; Ober, Curtis C.; Rodacy, Philip J.; Nelson, C.L.

Ultrasonic wave propagation decreases as a material is heated. Two factors that can characterize material properties are changes in wave speed and energy loss from interactions within the media. Relatively small variations in velocity and attenuation can detect significant differences in microstructures. This paper discusses an overview of experimental techniques that document the changes within a highly attenuative material as it is either being heated or cooled from 25°C to 90°C. The experimental set-up utilizes ultrasonic probes in a through-transmission configuration. The waveforms are recorded and analyzed during thermal experiments. To complement the ultrasonic data, a Discontinuous-Galerkin Model (DGM) was also created which uses unstructured meshes and documents how waves travel in these anisotropic media. This numerical method solves particle motion travel using partial differential equations and outputs a wave trace per unit time. Both experimental and analytical data are compared and presented.

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TYPE Conference Poster YEAR 2015
ScopusOSTIDOI

Validation of carbon-fiber laminate simulations with low velocity impact experiments

CAMX 2014 - Composites and Advanced Materials Expo: Combined Strength. Unsurpassed Innovation.

English, Shawn A.; Nelson, Stacy M.; Krafcik, Karen L.; Moore, David G.; Kernen, Burke L.; Briggs, Timothy B.

Presented is a model verification and validation effort using low velocity impact (LVI) of carbon fiber reinforced polymer laminate experiments. The flat cylindrical indenter impacts the laminate with enough energy to produce delamination, matrix cracks and fiber breaks. Included in the experimental efforts are ultrasonic scans of the damage for qualitative validation of the models. However, the primary metrics of validation will be the force time history measured through the instrumented indenter and initial and final velocities. The simulations, which are run on in-house software, will consist of all physics and material parameters of importance as determined by a sensitivity analysis conducted on the full LVI simulation. The orthotropic damage and failure constitutive model used for the lamina is described in detail and material properties are measured, estimated from micromechanics or optimized through calibration. For all simulations of interest, the mesh and material behavior is verified through extensive convergence studies. An ensemble of simulations incorporating model parameter uncertainties is used to predict a response distribution which is then compared to experimental output. The result is a quantifiable confidence in material characterization and model physics when simulating this phenomenon in structures of interest.

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TYPE Conference Poster YEAR 2014
ScopusOSTI
Results 76–100 of 108
Results 76–100 of 108