Effects of a Powder Application Process on the Material Properties of Fiber-Reinforced Polymer Composites
Incorporating solid microparticle additives in fiber-reinforced polymer composites (FRPs) is critical for expanding the functionality and potential applications of FRPs. The typical FRP manufacturing processes used to inject or infuse particle-containing resins into dry fiber reinforcements often encounter difficulties due to increased viscosities and filtering of particles. To overcome these issues, a sieve-based powder application system, layer-by-layer (LbL) processing, had been previously conceptualized and prototyped at Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM). However, the viability of this process in comparison to an established method of FRP manufacturing, in this case one-step vacuum infusion, through evidence of commensurate FRP properties had yet to be confirmed. In this thesis, the effects of the manufacturing method, homogeneity of powder distribution, and concentration of aluminum oxide hydroxide solid microparticles in LbL processing were investigated by a comparison of physical and mechanical properties of cured FRPs. Following process parameter identification, basalt fiber-reinforced polybenzoxazines were produced via LbL processing with oven or autoclave-curing, as well as one-step-vacuum infusion. Cured FRP densities, thicknesses, theoretical fiber volume contents, morphologies, flexural strengths and moduli, and fracture strains were analyzed. On almost all FRP properties the manufacturing method had the most significant effect, with vacuum-infused and LbL autoclaved-cured samples demonstrating comparable properties. Powder homogeneity influenced only apparent interlaminar shear strength, and additive concentration most greatly affected fracture strain and modes of failure. These results suggest that LbL processing with autoclave curing provides a comparable and robust alternative to infusion of basalt-fiber reinforced polybenzoxazines through which solid particle additives can be incorporated.
Bremen, Univ., Master Thesis, 2020