Fiber Waviness and Other Mesostructures in Filament Wound Materials

Glass-epoxy filament windings were made with circular and hexagonal sections. They were sectioned and examined for fiber angular deviations and packing anomalies. Results were compared with those from a carbon-epoxy commercially wound circular section tube. In addition, flat regions from the hexagonal section tubes were tested using the short beam shear test. It was found that in-plane waviness was usually much more serious than out-of-plane, especially with the commercial tube. Winding pressure appears to be very important when tubes are not consolidated after winding. Thus the hexagonal sections had very high void contents (here the winding pressure is negligible) and the unsupported hexagonal section windings had relatively low fiber volume fractions. The apparent shear strength was reduced by the voids, but did not correlate with any other mesostructural parameter, nor with fiber volume fraction.