MATERIALS SCIENCE: An Inside View of Weaving

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Science  24 Aug 2007:
Vol. 317, Issue 5841, pp. 1010d-1011d
DOI: 10.1126/science.317.5841.1010d

Fiber-reinforced composites (FRCs) are finding increasing use as structural materials because they offer good performance at low weights. The mechanical properties of any given FRC depend on many variables, including the distribution and orientation of the fibers within the matrix material. However, for most composites, nondestructive visualization of the fibers' response to stresses is precluded either by the opacity of the matrix material or by insufficient contrast between the fibers and the matrix.

Davies et al. surmount this challenge by probing an FRC through diffraction of a high-flux, microfocused x-ray beam from a synchrotron source. The sample comprised woven poly(p-phenylene phthalamide) (PPTA) fiber mats embedded in an epoxy matrix. A hole drilled into the center of the specimens modeled the rivet holes typically used to attach composite panels in aeronautical applications. The diffraction data clearly resolved the interleaved pattern of the woven fibers. Damage to the fibers was localized near the hole, and the tilt angle increased for fibers parallel to the strain direction as the stresses were transferred to neighboring fibers away from the hole. Because PPTA forms oriented fibers, the authors were able to determine changes in orientation of the yarn and could thus observe reorientation of the horizontal fibers caused by stress transfer. — MSL

Appl. Phys. Lett. 91, 044102 (2007).

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