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Alumina nanoparticles were successfully functionalized with a bi-functional coupling agent, (3-methacryloxypropyl)trimethoxysilane (MPS), through a facile neutral solvent method. MPS was found to be covalently bound with the nanoparticles. The linked MPS was polymerized with a vinyl-ester resin monomer through a free radical polymerization. Atomic force microscope phase images showed a uniform distribution of nanoparticles. Microtensile test results revealed the Young's modulus and strength increasing with particle loading. Microscopic examinations revealed the presence of large plastic deformations at the micron scale in the nanocomposites in agreement with the observed strengthening effect of functionalized nanoparticles. Thermo-gravimetric analysis (TGA) did not show any significant change in the thermal degradation of the nanocomposite as compared with the neat resin. The polymer matrix effectively protected the alumina nanoparticles from dissolution in basic and acidic solutions.

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A quick recovery: A semitransparent composite conductor comprising a layer of silver nanowire percolation network inlaid in the surface layer of a Diels-Alder-based healable polymer film is fabricated. The composite is flexible and highly conductive, and is capable of both structural and electrical healing via heating. Cut samples that completely lose their conductivity can recover 97% of it within 5 minutes of heating at 110 °C. The cutting and healing can be repeated at the same location for multiple cycles.

Complementary elastic energy density is used to derive a stress-strain relation, which is linear in uniaxial loadings in the longitudinal and trans verse directions, but nonlinear in shear. In the case of composite laminae under plane stress, one additional fourth-order constant is introduced. Comparison is shown between the present theory and experimental data on off-axis tests.

In the production of composite parts the pertinent processing parameters are time, temperature, and pressure. A judicious choice of these three parameters pro duces composites which are fully cured, compacted, and of high quality. Slight deviations from the recommended processing conditions can result in unacceptable quality. One of the most significant problems in the processing of composites is residual stresses. Processing-induced residual stresses can be high enough to cause cracking within the matrix even before mechanical loading. This microcracking of the matrix can expose the fibers to degradation by chemical attack. Strength is adversely affected by residual stresses since a pre-loading has been introduced. The topics considered and discussion presented in this paper have been chosen to ad dress the issue of understanding how residual stresses develop during processing and how they can be predicted. A process model has been developed which can be used to predict the residual stress history during the curing of composite laminates. This model includes the effects of chemical and thermal strains and assumes the material to exhibit linear, vis coelastic behavior. A phenomenological model is used to predict the degree of cure history during the cure cycle. Mechanical properties are allowed to develop based on a functional dependence on the cure state (degree of cure) and the transverse compliance is taken as the only time-dependent compliance. Simultaneous application of the cure kinetics and a vis coelastic stress analysis yields the residual moments and curvatures for unsymmetric cross-ply laminates. An experimental correlation is provided in an accompanying paper.

Most commercial copper nanoparticles are covered with an oxide shell and cannot be sintered into conducting lines/films by conventional thermal sintering. To address this issue, past efforts have utilized complex reduction schemes and sophisticated chambers to prevent oxidation, thereby rendering the process cost ineffective. To alleviate these problems, we demonstrate a reactive sintering process using intense pulsed light (IPL) in the present study. The IPL process successfully removed the oxide shells of copper nanoparticles, leaving a conductive, pure copper film in a short period of time (2 ms) under ambient conditions. The in situ copper oxide reduction mechanism was studied using several different experiments and analyses. We observed instant copper oxide reduction and sintering through poly(N-vinylpyrrolidone) functionalization of copper nanoparticles, followed by IPL irradiation. This phenomenon may be explained by oxide reduction either via an intermediate acid created by ultraviolet (UV) light irradiation or by hydroxyl (-OH) end groups, which act like long-chain alcohol reductants.

Recently, layered silicates have attracted attention as reinforcements in polymer nanocomposites. The addition of silicates enhances the mechanical properties, thermal stability, flame retardancy, and barrier properties of the polymer with only a small addition of nanoclay material.[1±7] This is attributed to the high aspect ratio and available surface area of the silicate layers. Theoretical work has shown that the addition of materials with a sufficiently large aspect ratio can significantly enhance the mechanical strength of a composite. [8] Graphite is a layered material consisting of one-atom-thick sheets of carbon. By separating the graphite layers through intercalation and exfoliation, thin nanoplatelets can be formed which possess a high surface area and satisfy the high-aspectratio criterion needed for high-strength composites. The theoretical surface area of a graphite sheet is 2630±2965 m 2 g ±1 . [9,10] In addition to its unique chemistry, graphite is also one of the strongest materials known per unit weight. The theoretical Young's modulus of an individual graphite sheet is 1060 GPa. [11,12] Therefore, their layered morphology and light weight make graphite nanoplatelets a potential reinforcement for high-strength materials. Graphite nanoplatelets (GNPs) were synthesized using known graphite-intercalation chemistry.[13] A simplified schematic of the intercalation and exfoliation process is shown in Figure 1. The first-stage intercalation compound, KC 8 , is readily formed by heating graphite powder with potassium metal under vacuum at 200 C. Powder X-ray diffraction confirms that the only crystalline material present is KC 8 . A c-axis expansion from 3.4 to 5.4 is calculated from the diffraction pattern. Note that an average stoichiometric distribution of potassium within the graphite galleries is most likely achieved, rather than the idealized first-stage intercalation compound depicted in Figure 1. Graphite is intercalated with potassium to form the first-stage intercalation compound, KC 8 , and then exfoliated in aqueous solvent to produce GNPs that are 40 ± 15 layers thick.