## 3 Composite Laminates Toughened by Nano-Particles  
Over the past decades, considerable research efforts have been devoted to disperse nanoparticles into polymeric composites in order to enhance their toughness [53]. As illustrated in Figure 10, a brittle  
Figure 9: Decreased damage parameter caused by various nanofibers. polymer (\(G_{\text{IC}}\) less than 200 J/m\({}^{2}\)) has more improvement in the fracture toughness of composite, compared with a tough polymer [54]. For the brittle polymer, the increased toughness in the composite was attributed to the fiber breakage and pullout that generally accompany composite crack growth. The low transfer efficiency of resin fracture toughness into delamination fracture toughness, for very ductile resins, is the result of the constraint on the development of a larger plastic zone in the resin-rich region between plies by the fibers in the adjacent plies [55]. A positive relationship is reported between the improvement fracture toughness, the increase of impact performance and the enhancement of the residual strength of composite materials [56], as the onset and propagation of delamination are largely affected by fracture toughness values of composite laminates. This section reviews some recent developments in the use of nanoparticles as additional reinforcing phases in fiber-reinforced epoxy matrix composites, addressing the effects of nano-modified epoxy matrices on impact and CAI strength of fiber-reinforced laminates. The behaviors of nanoparticles strongly depend on the sizes, shapes, dimensionality and morphologies. A highlighted summary of recent works on improving the toughness and impact performance of composites is shown in Table 2. Reinforcing nanoparticles are classified into zero-, one-, two- and three-dimensional (3D) structures [57; 58] as exemplified in Figure 11, and the related works are summarized in the following. Figure 10: Mode I interlaminar fracture toughness of composites and matrix toughness [54]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** & **Particle Type** & **Composite Type** & **Test Method** & **Improvement (\%)** & **Content** \\ \hline
[99] & Nanosilica & Epoxy & Compact tension & & \\  & & & ASTM Standard D5045-02 & & \\ \hline  & & & Un-method Chappy & & \\
[60] & Nanosilica & Epoxy & DIN-BO-179-2 & & \\  & & & Compact tension & & \\  & & & ASTM Standard D5045-02 & & \\ \hline  & & & DCB (ASTM D-3433) & & \\
[61] & Fullerene-like tungsten & Epoxy & T-ped joints (ASTM D-1876) & & \\  & & & Chappy impact (ASTM D-950) & & \\ \hline  & & & & & \\
[62] & Aluminum oxide & Epoxy & Elevant testing ENSO 178 & \(\text{G}_{\text{C}}\) increased by 120\% & 10 vol \% \\ \hline  & & & & & \\
[63] & Alumina Nanofiliers & Epoxy & Tensile ASTM D-638 & & \\  & & & Compact tension & & \\ \hline  & & & DCB (887273) & & \\
[64] & Rubber & Carbon/epoxy & ENF (BMS 8-276) & & \\  & & & Impact and CAI (B857260) & & \\ \hline  & & & & & \\
[65] & Nanosilica and & Carbon/epoxy & DCB ASTM Standard D5528 & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\
[66] & Nano-silica & Carbon fiber/epoxy & DCB ASTM Standard D5528 & & \\  & & & & & \\  & & & & & \\  & & & & \\
[67] & Nanosilica & Epoxy & The single-edge method based (SENB) test & & \\  & & & ISO-13866 & & \\ \hline  & & & & & \\
[68] & Rubber and silica & Carbon/epoxy & DCB ASTM D5528, & & \\  & & & ENF DIN EN 6034 & & \\  & & & & & \\  & & & & & \\  & & & & \\  & & & & & \\
[69] & Nanosilica & Class/epoxy & Charry impact tests & & \\  & & & & & \\  & & & & \\  & & & & & \\ \hline  & & & & & \\
[70] & Nanosilica & Carbon/epoxy & Ballistic impact & & \\ \hline  & & & & & \\ \end{tabular}
\end{table} 
Table 2: Published paper regarding the influence of nanoparticles on fracture toughness and impact response of composite laminates.