Influence of various forms of polypropylene matrix (fiber, powder and film states) on the flexural strength of carbon-polypropylene composites

An investigation into the flexural properties of unidirectional composites (UDC) produced from blending of carbon fiber and polypropylene (PP) matrix in varying forms of fiber, powder and film are reported. Dr. Ernst Fehrer (DREF) friction spun hybrid yarns were manufactured from PP fibers and carbon tows, and were consolidated to yield UDC-D. PP powder was layered on carbon tows by electrostatic spray coating and were consolidated to form UDC-P. A third laminate, UDC-F was manufactured by the consolidation of PP films stacked between carbon tows. The fiber volume fraction was similar to 50% in all the three UDCs. Better mechanical properties of UDC-P were observed in 3-point bending and short beam tests. Analysis by micro-computed tomography, and scanning electron microscopy indicate better impregnation of PP powder in UDC-P despite higher viscosity of PP powder than PP fiber, and thereby higher interlaminar strength. This is the first work reported on comparison of laminates from powder coating versus DREF and film stacking.