The effect of three different alkylammonium-modified montmorillonite on morphological and mechanical properties of glassy epoxy-amine nanocomposites is reported. Small amounts of clays <10 phr (part per hundred of resin) were used in each system of nanocomposite. The morphology of the prepared nanocomposites was performed by means of X-ray diffraction and transmission electron microscopy. Differential scanning calorimetry (DSC) was used to investigate the glass transition temperatures (T g ). Mechanical properties were based on tensile characteristics (Young's modulus), impact strength, and fracture toughness. The measured moduli were com-pared to theoretical predictions. Scanning electron microscopy was used to study the morphological structure of the fracture surfaces of impacted specimens. It was found that at a low content of 2 phr (1.2 wt %) of nanoclays, the impact strength and the fracture toughness were improved by 77 and 90% respectively, comparatively to the neat epoxy, whereas DSC revealed a reduction of the T g of nanocomposites.

In this study, a new kind of hybrid material was prepared from various amounts of silane surface modified alumina nanoparticles, oxidized ultra high molecular weight polyethylene (UHMWPE) fibers, and epoxy resin. The reinforcing phases were selectively treated to achieve a fully connected network aiming an effective stress transfer between the constituents. The efficiency of the grafting mechanisms was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The developed hybrid materials were tested for their mechanical, thermomechanical, and ballistic performances. The mechanical results, namely tensile and bending, confirmed the positive effects of increasing the nanofillers amounts up to 5 wt%. The thermochemical properties analyzed by dynamic mechanical analysis (DMA) revealed consequent improvements in the storage modulus and glass transition temperature upon the addition of the nanophase. In the meantime, the ballistic tests evaluated under the National Institute of Justice standard (NIJ standard-0101.06-IIA) also highlighted an improved kinetic energy absorption following the increase in the amounts of the discontinuous phase. Subsequent experimentations precisely quantified the required number of plies for an effective projectile stopping under the chosen standard. Overall, this study unraveled for the first time ever the benefits obtained from a fully connected hybrid network under both static and dynamic loads.

In this study, a new high-performance hybrid material was designed targeting an efficient ballistic and nuclear shielding protection. To achieve this goal, a typical highly performant thermosetting resin, namely the phthalonitrile (PN) resin, was reinforced with Kevlar fibers (KF-29), as continuous phase, and erbium oxide (Er2O3) nanoparticles, as discontinuous phase. The reinforcing phases underwent a silane surface modification to create a fully connected network aiming an improved stress transfer between the constituents. The mechanical investigations through tensile and bending testing confirmed the positive effect of the addition of an increasing amount (up to 20 wt%) of the Er2O3 nanoparticles. The hybrids also provided excellent gamma rays shielding performances with a screening ratio of about 33% for a 3 cm thick sample. In the meantime, the ballistic tests evaluated under the National Institute of Justice standard (NIJ standard-0101.06-IIA) also highlighted an improved kinetic energy absorption following the increase in the amounts of the discontinuous phase. Overall, this study unraveled for the first time ever the benefits obtained from a fully connected hybrid network in the field of ballistic and radiation protection.

In this study, new high-performance composite laminates were prepared from epoxy resin and surface modified ultrahigh-molecular-weight polyethylene (UHMWPE) fibers. The UHMWPE fibers underwent two types of chemical modifications, namely through chromic acid and potassium permanganate oxidations. The adopted chemical procedure aimed the grafting of polar groups on the outer surface of fibers for an improved chemical and physical compatibility with the polymeric matrix. The efficiency of the grafting methodology was confirmed by vibrational, thermal, and morphological analyses, and the grafting mechanism was thoroughly discussed. Furthermore, composite laminates were prepared to study the effects of chemical treatments on the mechanical and morphological properties of the resulting composites. The grafting techniques allowed consequent improvements in the tensile and bending properties, up to 34% and 23% for the tensile and flexural strengths, respectively. The study of the fractured surfaces confirmed the exceptional compatibility between the fillers and the polymeric matrix and further corroborated the mechanical findings. Finally, the adopted modification techniques can be regarded as cost-effective and highly suitable for the manufacturing of structural composites for advanced applications.

Lead-based bullets are the major type of ammunition used all over the world. The high toxicity of this heavy metal directly affects the personnel manufacturing the projectiles and causes the contamination of the shooting ranges. To provide remedy, this work proposes cost-effective and highly performant polymer-based bullets intended to replace the traditional lead-based ones in a multitude of conventional weapons. The proposed new projectiles were elaborated from a high-performance phthalonitrile resin and several amounts of silane surface-modified chopped carbon fibers and bismuth oxide nanoparticles. The newly developed bullets were manufactured and tested for their precisions at 50 m and their velocities at 2 m from the barrel. The obtained results showed exceptional precisions with high velocities. Furthermore, the mechanical, thermal, and morphological investigations further confirmed the superior performances of these exceptional materials. It can be inferred that the produced bullets are suitable for ammunitions intended to be used for close combat and self-defense situations.