<p class="MsoNormal" style="text-align: justify">Due to their high strength in conjunction with low weight we observe an ongoing trend to use short fiber reinforced plastic parts in technical systems. Fiber volume content, fiber length and the fiber orientation defines the key mechanical materials properties, such as strength an E-modulus. Whereas fiber length and average fiber volume content can be controlled within the manufacturing process, it turns out that the fiber orientation can significantly differ from optimal fiber alignment at critical areas in vicinity of holes, edges or welding seams because of the complex resin flow during the filling process. The fiber orientation then does not only result in lower strength but also experiences lower local shear modulus distribution. Provided the components density is well known the shear moduli can be calculated by measuring the fiber orientation and the shear wave velocity. In this work we set up a special probe with two perpendicular shear elements generating shear waves with two perpendicular polarizations. In doing so the polarization angle can be controlled electronically. The fiber orientations can be determined by rotating the polarization plane stepwise from 0 to 360° and measuring phase and amplitude of the backwall reflection. In our experiments we measured the shear modulus of a unidirectional reinforced GFRP of 3.1 GPa (fiber volume content 52.5%). Comparing with the findings of the destructive testing we found a fairly nice deviation of less than 10&nbsp;%. &nbsp;The method was also used to determine the critical stage of the degradation process in cyclic loading test of GFRP specimen.</p>

Materials Characterization of Fiber Reinforced Plastic Using Polarized Shear Waves

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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