Developing Superperforming Composites by Harnessing Fiber Orientation and Processing Technology.

The current research on the development and performance evaluation of unique composites focuses on an unexplored combination of fibers of PBO (polybenzoxazole Zylon) as reinforcement and PEEK (polyetheretherketone) as a matrix. Their fibers were braided in equal ratios and then compression-molded to develop composites by manipulating all long fibers in one direction (unidirectional, a UD composite) and for the other one half in one direction and the remaining half in the perpendicular direction (bidirectional, a BD composite). The performance was evaluated by hardness (micro- and scratch) studies followed by tensile and impact strength. Furthermore, the lap shear strength of the adhesive joints developed with these fibers in various orientations was also analyzed. The performance properties were compared with those of neat PEEK. It was observed that an exceptional increase compared to neat PEEK in impact strength of 10,000% and tensile strength of 662% was achieved in the case of the UD composite. Scanning electron microscopy (SEM) and microcomputed X-ray tomography were used on failed specimens to analyze the reasons for failure.

Assimilation of Nanoparticles of SiC, ZrC, and WC with Polyaryletherketone for Performance Augmentation of Adhesives.

The present paper reports the analyses of results obtained from experiments carried out to explore the challenge of homogeneous, uniform, and deagglomerated dispersion of ultra-heavy nanoparticles (NPs) in the high-performance polyaryletherketone (PAEK) matrix. An equal and fixed amount of (0.5 vol. %) NPs of silicon carbide (SiC), zirconium carbide (ZrC), and tungsten carbide (WC) were dispersed in a PAEK matrix and compression molded to develop three different nanocomposites. Simultaneously, nano-adhesives of the same composition were also developed to join the stainless steel adherends. The composites and adhesives were characterized for their physical, thermal, thermo-mechanical, thermal conductivity (TC), and lap shear strength (LSS) behavior. It was observed that SiC NPs performed significantly better than ZrC and WC NCs in all performance properties (LSS: 154%, TC: 263%, tensile strength: 21%). Thermal conductivity (TC) and tensile properties were validated using various predictive models, such as the rule of mixture parallel model, the Chiew and Glandt model, and the Lewis model. Scanning electron micrographs were used for the morphological analysis of LSS samples to detect macro- and micro-failure. Micrographs showed evidence of micro-striation and plastic deformation as a micromodel, as well as mixed failure, i.e., adhesive-cohesive as a macro-failure mode.

Carbon Fabric Decorated with In-Situ Grown Silver Nanoparticles in Epoxy Composite for Enhanced Performance.

The current study focuses on studying the effect of reinforcement of carbon fabric (CF) decorated with in-situ grown silver (Ag) nanoparticles (NPs) on the performance properties of epoxy composite. The Ag NPs were grown on carbon fabric by reducing silver nitrate. The main objective of developing such an innovative reinforcement was to improve thermal conductivity, interlaminar strength, and tribological properties of CF-epoxy composites. The growth of NPs on the surface of CF was confirmed through scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDAS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction studies. The development of composites was conducted by the impregnation method, followed by compression molding. It was observed that in-situ growth of Ag NPs enhanced thermal conductivity by 40%, enhanced inter-laminar shear strength by 70%, enhanced wear resistance by 95%, and reduced the friction coefficient by 35% in comparison to untreated CF.

Performance Augmentation of Epoxy Adhesives with TiN Nanoparticles.

In the current study, nanoparticles (NPs) of titanium nitride (50-70 nm) in varying amounts (0-4 wt %) were uniformly suspended in an epoxy solution and then used to cast the films of nanocomposites. The same formulations were used to prepare the lap shear strength joints using stainless-steel coupons with the help of standard molds and then employing the compression molding technique. The nanocomposites films were characterized for their physical properties, thermal stability, friction performance, and scratch hardness, while the lap shear strength of joints prepared using nanocomposites as nanoadhesives was evaluated. The failed surfaces of joints were investigated using scanning electron microscopy (SEM) to understand the failure modes, that is, micro-failure mechanisms, while the cross-sectional surfaces of fractured nanocomposites were investigated using SEM to identify the distribution of NPs. The increase in the contents of NPs in the epoxy led to an almost linear increase in the selected performance properties. The highest (70%) improvement in the lap shear strength was observed with 4 wt % NPs, which was correlated with an increase in the hardness of composites.

Use of the vacuum-assisted closure device in enhancing closure of a massive skull defect.

OBJECTIVES/HYPOTHESIS: The objective was to describe a novel technique for reconstructing the cranial vertex without the use of free tissue transfer. STUDY DESIGN: Case report, literature review, and discussion. METHODS: A 50-year-old woman presented from a remote Pacific Island community with a 12 x 14-cm, necrotic, grossly contaminated eccrine gland carcinoma of the cranial vertex that extended through the calvarium but did not invade the dura. Following tumor extirpation, the resulting bony defect was 10 x 12 cm in size, with a concomitant scalp defect of 14 x 16 cm. Free tissue transfer was impossible because of severe intimal peripheral vascular disease, posing a challenging reconstructive dilemma. After tumor resection, the bony edges were covered with local scalp flaps and the vacuum-assisted closure device was placed over the wound at a constant setting of -50 mm Hg. The vacuum-assisted closure device was changed three times per week for 3 weeks. RESULTS: A thick, 1-cm bed of granulation tissue developed over the dura, allowing temporary coverage by a split-thickness skin graft, and the scalp defect decreased in size by approximately 25%. The patient did not develop meningitis, headache, or localized infection as a result of placement of the vacuum-assisted closure device and tolerated the vacuum-assisted closure well. After a requisite period of healing, tissue expanders and calvarial reconstruction will be performed. CONCLUSION: Use of the vacuum-assisted closure device is a safe, reliable adjunct in the closure of large cranial defects with exposed dura and offers a novel reconstructive option for complex defects of the head and neck.