11 April 2013 The influence of multi-mode failures in composites on the characteristics of elastic waves
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Based on the micromechanical approaches, high frequency elastic waves are generated in carbon fiber/polymer composites due to three main damage sources as fiber breakage, matrix crack or delamination. The occurrence of damage mode depends on the ratios of energy release rates. Simultaneous generation of damage modes such as multiple fiber breakage called as fiber fragmentation influences the characteristics of propagating elastic waves which are used for detecting, locating and understanding damage modes for acoustic emission method. Understanding the wave characteristics via experimental methods is difficult as the control of damage mode sequence is a challenge. In this paper, wave propagations due to single or multiple fiber breakages positioned at various locations along the laminate and through thickness in different composite lay-ups are studied using dynamic finite element models. Fiber breakage is defined as a point load with the rise time of 1 μsec. The load amplitude is identified using stress-strain curve of carbon fiber. The amplitude of matrix cracking is defined as crack opening displacement as a boundary load to the finite element model. The positions and amplitudes of damage modes are varied to understand the characteristics of waveform signatures. Each lamina is defined as a different plate and orthotropic material properties are entered as input to the model. The paper shows that multi-mode simultaneous damage in composites causes complex waveform generation, which makes pattern recognition based on amplitude and frequency real time a challenging task.
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Lu Zhang, Lu Zhang, Didem Ozevin, Didem Ozevin, "The influence of multi-mode failures in composites on the characteristics of elastic waves", Proc. SPIE 8694, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2013, 869402 (11 April 2013); doi: 10.1117/12.2009244; https://doi.org/10.1117/12.2009244

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