2.3 Nanofillers 45 Epoxy resin Carbon fiber Nanostructured interlaminar interface Figure 2.11.Schematic illustration of interlaminar interface nanostructuring since the nanoparticles cause the pore structure in the concrete to be relatively fine,thereby reducing the porosity at the interface between the concrete and the steel rebars.In another example,the addition of carbon black (nanoparticles around 30nm in size)to the interlaminar interface of a continuous carbon fiber polymer-matrix composite (Figs.1.1 and 2.8)improves the through-thickness compressive modulus of the composite.Nanofillers are also useful for surface modification,such as the modification of the surface of a composite material for the purpose of increasing the wear resistance.Figure 2.11 illustrates both surface nanostructuring and interlaminar interface nanostructuring.In surface nanostructuring,the nanofiller is positioned on the surface rather than at the interlaminar interface. Nanofillers are attractive for use as secondary fillers in composites that contain primary fillers(e.g.,continuous carbon fibers)that serve as the load-bearing com- ponent in the composite.The secondary filler serves to enhance certain proper- ties other than the load-bearing ability.For example,it may enhance the vibration damping capacity due to the large amount of nanofiller-matrix interface area per unit volume;the slight slippage at these interfaces during vibration causes mechan- ical energy dissipation.The nanofiller can be mixed with the matrix(e.g.,the epoxy resin)prior to using the matrix in composite fabrication,though this approach suf- fers from increased viscosity of the resin (due to the presence of the nanofiller), which makes it more difficult for the resin to penetrate the small space between adjacent continuous fibers.Alternatively,the nanofiller is positioned at the inter- laminar interface between the laminae of continuous fibers(Figs.1.1 and 2.11). Review Questions 1.Describe the crystallographic texture of a carbon fiber. 2.From the viewpoint of the chemical bonding,explain why graphite is a good lubricant. 3.From the viewpoint ofchemical bonding,explain why diamond is mechanically very hard. 4.What are the three forms of carbon? 5.What is meant by turbostratic carbon?2.3 Nanofillers 45 Figure 2.11. Schematic illustration of interlaminar interface nanostructuring since the nanoparticles cause the pore structure in the concrete to be relatively fine, thereby reducing the porosity at the interface between the concrete and the steel rebars. In another example, the addition of carbon black (nanoparticles around 30nm in size) to the interlaminar interface of a continuous carbon fiber polymer-matrix composite (Figs. 1.1 and 2.8) improves the through-thickness compressive modulus of the composite. Nanofillers are also useful for surface modification, such as the modification of the surface of a composite material for the purpose of increasing the wear resistance. Figure 2.11 illustrates both surface nanostructuring and interlaminar interface nanostructuring. In surface nanostructuring, the nanofiller is positioned on the surface rather than at the interlaminar interface. Nanofillers are attractive for use as secondary fillers in composites that contain primary fillers (e.g., continuous carbon fibers) that serve as the load-bearing com￾ponent in the composite. The secondary filler serves to enhance certain proper￾ties other than the load-bearing ability. For example, it may enhance the vibration damping capacity due to the large amount of nanofiller–matrix interface area per unit volume; the slight slippage at these interfaces during vibration causes mechan￾ical energy dissipation. The nanofiller can be mixed with the matrix (e.g., the epoxy resin) prior to using the matrix in composite fabrication, though this approach suf￾fers from increased viscosity of the resin (due to the presence of the nanofiller), which makes it more difficult for the resin to penetrate the small space between adjacent continuous fibers. Alternatively, the nanofiller is positioned at the inter￾laminar interface between the laminae of continuous fibers (Figs. 1.1 and 2.11). Review Questions 1. Describe the crystallographic texture of a carbon fiber. 2. From the viewpoint of the chemical bonding, explain why graphite is a good lubricant. 3. Fromtheviewpointofchemicalbonding,explainwhydiamondismechanically very hard. 4. What are the three forms of carbon? 5. What is meant by turbostratic carbon?