Query: aerogel glass mat composites

title: Effect of aging on thermal conductivity of fiber reinforced aerogel composites: An X ray tomography study
abstract: Silica aerogels display an ultra low thermal conductivity (l) and are used as thermal superinsulators. Here, we study the influence of aging and drying processes on the microstructure and thermal conductivity of fiber reinforced silica aerogel composites. Glass wool silica gel composites were aged for variable times, hydrophobized, and dried either at ambient pressure or from supercritical CO2 (scCO2) The X ray micro tomographic data display three distinct phases: silica aerogel, glass fibers, and macroscopic pores and cracks. The silica aerogel appears as a continuous medium in the tomograms because the spatial resolution (6 11 mm) is insufficient to resolve the aerogel mesopores ~0.02 0.10 mm) For the composites prepared by ambient pressure drying, insufficient aging led to prominent drying shrinkage and cracking, and a high macro porosity, as quantified by 3D image analysis. Insufficient aging also led to an increase in l from 15.7 to 21.5 mW m 1 K 1. On the contrary, composites that were nearly free of cracks and displayed a constant l of 16.3 0.8 mW m 1 K 1 could be prepared by scCO2, independent of aging time. The thermal conductivity was reproduced from the macro porosity to within 0.7 mW m 1 K 1 using simple thermal transport models consisting of thermal elements connected in series or parallel. Our results illustrate the usefulness of X ray micro tomography to quantify the 3D microstructure and its effects on the bulk composite properties and the data highlight the importance of aging for the production of low l aerogel fiber composites by ambient pressure drying.

title: Dispersion of polymeric coated silica aerogel particles in unsaturated polyester composites: Effects on thermal mechanical properties
abstract: The thermal mechanical properties of unsaturated polyester (UP) composite were enhanced by the dispersion of silica aerogel (SA) with preserved pores. Low cost SA was prepared from rice husk via the sol gel process and ambient pressure drying. A new method was proposed to encapsulate the hydrophobic aerogel surface pores with hydrophilic polyvinyl alcohol (PVA) film using the fluidized bed coating process. The dispersion of PVA coated aerogel with preserved pores in the polyester matrix resulted in an increase of specific compressive strength (44.1 MPa cm3 g 1) thermal insulation (0.23 W m 1 K 1) and thermal stability (Tonset 310degC) but decreased the glass transition temperature (Tg 260degC) GRAPHICAL

title: Biocomposites of copper containing mesoporous bioactive glass and nanofibrillated cellulose: Biocompatibility and angiogenic promotion in chronic wound healing application.
abstract: Biocomposites of copper containing mesoporous bioactive glass (Cu MBG) and nanofibrillated cellulose (NFC) were designated as potential dressing material for chronic wound healing. The phase composition and mesoporous micro structure of the synthesized Cu MBGs were elaborately characterized by combining several techniques, including TEM, SEM, XRD, SXAS and N2 physisorption. High bioactivity of the Cu MBG was confirmed in stimulated body fluids in vitro. A controlled dissolution of Cu from the glass suggests Cu MBG a suitable source for Cu release in wound healing dressings. Depending on the content of Cu MBG in the composite formulation, the composites were fabricated as membranes and aerogels. In biocompatibility assessment of the composites, a dose dependent cytotoxicity of Cu2+ on 3T3 fibroblasts was found. Importantly, a critical biological level of Cu2+ below 10mg/L was suggested for the survival and growth of 3T3 fibroblasts. The Cu2+ released from the composite aerogel of NFC and Cu MBG showed a profound angiogenic effect in the 3D spheroid culture system of human umbilical vein endothelial cells. Moreover, the angiogenic gene expression of 3T3 fibroblast was upregulated in the real time quantitative PCR analysis, which also confirms that the incorporation of Cu MBG into NFC matrix enhances the proangiogenic potential of the biocomposites. In addition, composites of NFC and Cu MBG also showed an inhibiting effect on the growth of E. coli.  To address an urgent need in clinics on developing a new generation of therapeutic dressings with advanced functionalities, this study has exploited the utilization of Cu containing mesoporous bioactive glass in the nanocellulose matrix to release Cu2+ as therapeutic ions for its angiogenic effect on promoting wound healing. This manuscript reports research work on biomaterial design, fabrication development, material characterizations and bioassessments in 2D cellular studies. To utilize nanocellulose derived from the wood resource in biomedical applications is of great significance, due to its vast availability and bioeconomy competence. The use of Cu containing bioactive glass in tissue engineering scaffolds, including wound healing, is an intriguing research topic, which has been recently discussed in the field of biomaterials. I think that our manuscript title with 'Biocomposites of copper containing mesoporous bioactive glass and nanofibrillated cellulose: biocompatibility and angiogenic promotion in chronic wound healing application' will make its own contribution on understanding the complex effects of Cu2+ on wound healing relevant events with acceptable novelty for Acta Biomaterialia.

title: Thermal evaluation and simulation of glass wool/maerogel blanket
abstract: Aerogel blankets are composites of silica aerogel particles dispersed in a reinforcing fiber matrix that turns the brittle aerogel into a durable and flexible insulating mat. While aerogel blanket manufacture from either organic or inorganic material, they are still some concerns over current environmental issues which are common worldwide are global warming, greenhouse effect, and climate change. Awareness of this environmental concern has led to the rise in an effort to renew agricultural waste like RHA (rice husk ash) which is cheaper precursor or a simple method in ambient pressure. As part of this study, to produce an insulator; glass wool was modified by ambient pressure drying methods to fabricate the flexible aerogel blanket. In order to evaluate thermal resistance of aerogel blanket, a hot plate is used. The microstructure of these aerogel blankets are also investigated for better understanding of the production process. Knowledge of the thermo mechanical properties is important for the optimization of the design for these heterogeneous materials. In order to assess the aerogel blanket, some technics such as thermal gravimetric analysis (TGA) scanning electron microscopic (SEM) and Fourier Transform Infrared spectrum (FTIR) was done. Moreover a simple numerical micro model have been developed to predict the effective thermal conductivity of flexible aerogel blankets, which consist of fibers, aerogel particles and air pockets. This simulation has two parts. In the first part of simulation, the effective thermal conductivity of the aerogel composites is computed with different aerogel particles and different volume ratios using the finite element method. The numerical analysis of thermal conductivity is conducted by generating 3D models of the microstructure of the aerogel blanket. In the second part of model, the extracted result from the micro model is inputted to the real sized model to predict top surface temperature. Finally all experiment data are validated by a numerical real sized model. In this study, a flexible aerogel blanket shows very good thermal resistance compare to original glass wool which is around 35% improvement. In addition TGA reveals that Maerogel(r) can retard material decomposition of blanket from 270degC to 287degC. Moreover SEM and FTIR clearly show that there is a good bonding between SiO2 particles that make a strong network to tolerate high temperature and to be flexible blanket. Furthermore Maerogel(r) blanket structurally was simulated then was validated by experiment result that showed good agreement; there is a well matching between the data that were extracted from simulation and experiment.

title: Fabrication of Infrared Opacifiers Loaded Al2O3 Aerogel SiO2 Fiber Mat Composites with High Thermal Resistance
abstract: The infrared opacifiers loaded Al2O3 aerogel SiO2 fiber mat composites were fabricated by the sol gel process. The effects of the content of the TiO2 and SiC particles on thermal insulation perform.

title: Effect of poly(ether imide) blends on the physical properties of thermoplastic glass mat composites
abstract: Glass mat thermoplastic composites (GMTs) were prepared from poly(ether imide/poly(ethylene naphthalate) (PEI/PEN) and PEI/poly(ethylene terephthalate) (PET) blends using compression molding. The thermal stability, surface hardness, rheological, mechanical, and gas barrier properties and the coefficient of thermal expansion (CTE) for various composites were analyzed. Differential scanning calorimetric and thermogravimetric analysis showed that PEI blends with 30% PEN or PET retained 80% of the thermal stability of virgin PEI. PEI melt viscosity significantly decreased with addition of PEN and PET, which greatly improved impregnation during GMT manufacture. The tensile strength and CTE of GMTs containing up to 30% PEN or PET remained similar to that of PEI/GM, while the flexural modulus increased and the gas barrier properties improved two fold. Scanning electron microscopy confirmed that interfacial adhesion improved for surface modified GMs. We demonstrated that inexpensive GMTs could be prepared while retaining the superior properties of PEI.

title: On the Applicability of Thermoforming Characterization and Simulation Approaches to Glass Mat Thermoplastic Composites
abstract: Chopped fiber composite materials offer the potential to be used for complex geometries, including local thickness changes, ribs and beads, offering significant potential for functional lightweighting. Depending on the initial mold coverage and flowability of the material, the processing behaves either more like a compression molding or a thermoforming process. The latter is applicable to high initial mold coverages and includes typical thermoforming defects such as local wrinkling. Such defects are not predictable by conventional compression molding simulation approaches usually adopted for this material class. Therefore, thermoforming characterization and simulation approaches and their applicability to glass mat thermoplastic (47 vol. long glass fiber, Tepex Flowcore) for high initial mold coverages is investigated. Abaqus in combination with several user subroutines is applied. Valid material characterization results from torsion bar and rheometer bending tests are obtained and applied to an automotive structure in thermoforming simulation. Results indicate that the high stiffness and high viscosity captured by the rheometer bending test at low shear rates are necessary to reproduce the wrinkling behavior observed in the experimental results. Discrepancy is most likely reducible to thermomechanical effects, and that the modelling approach does not account for thickness deformation due to transverse compression.

title: Investigation of thermal insulation performance of glass/carbon fiber reinforced silica aerogel composites
abstract: Silica aerogels have been widely used as thermal insulators, but their fragility has hindered the potential applications. In this work, a novel way of improving aerogel skeletal structure was proposed where composites were reinforced by three functional layers of glass fiber (GF) carbon fiber (CF) Heat insulation performance of fiber reinforced aerogel composites was also investigated in a simulated solar radiation system. Composites composed of three layers of fiber were prepared by a sol gel process under ambient pressure drying. The results showed that, as three layers were all GF blankets, the composite heat conductivity increased with increasing glass fiber content. Flexural strength increased initially and reached a maximum at 20% glass fiber content before decreasing. To find a balance between promoting heat insulation performance and strengthening the composite structure, two layers of 5% glass fiber blankets were used as structure strengthening layers and one carding 5% carbon fiber as the heat insulation layer were recommended. Under these conditions, the composite showed extremely low thermal conductivity (0.031 W/m K) almost comparable to that of pure aerogel (0.036 W/m K) while maintaining high flexural strength (2.846 MPa) superior than previous studies. Composites with other ratios of glass/carbon fibers with sandwiched alignments also demonstrated better flexural strength and lower thermal conductivity than GF aerogel composites. This work provided an alternative way to prepare robust and sustainable heat insulation aerogel composites for practical uses. Heat insulation performance of silica aerogels composited with different ratios of glass fiber and carbon fiber was investigated. The flexural strength increased with increased glass fiber loading, and reached its highest value when glass fiber content was 20% 5% carbon fiber inserted between the two 5% glass fiber layers was found the most ideal condition in terms of flexural strength (2.846 MPa) and thermal conductivity (0.031 W/m K)

title: Mode II interlaminar fracture toughness of woven E glass/epoxy composites in the presence of mat interleaves
abstract: Composite laminates are widely used as primary load bearing structures in various industries. Using a thin layer of chopped strand mat between sub laminates of a thick structural composite laminate would prevent crack development across the whole laminate thickness and reduce the risk of catastrophic failure in the structure. In this research, end notched flexure (ENF) specimens were used to examine the impact of the mat layer between woven layers on the mode II interlaminar fracture toughness of glass/epoxy composites. ENF specimens are fabricated using hand lay up method assisted by vacuum bagging technique. Experimental results revealed that the existence of a mat interlayer resulted in a reduction of interlaminar fracture toughness of the delamination initiation and propagation by 59% and 35% respectively, compared to one without mat interlayer. Moreover, results showed that in the ENF specimens without interleaving of the mat, the dominant mechanism of increased fracture toughness is not fiber bridging and delamination propagates in fiber matrix interface in these specimens.

title: Effect of Glass and Banana Fiber Mat Orientation and Number of Layers on Mechanical Properties of Hybrid Composites
abstract: In this work, the effects of fiber mat orientation and number of layers on the tensile, flexural and impact properties of glass fiber random (SGFR) and banana fiber woven (BFW) mat reinforced epoxy laminated hybrid composites are investigated experimentally based on ASTM standards. The hybrid composites are prepared by compression molding process and results are compared with pure glass and banana fiber mat epoxy laminated composites. Results shows that introducing of SGFR mat in between the BFW mats in the epoxy laminated composites reduces the overall weight of the composites and the mechanical properties of the hybrid composites are varied with BFW mat orientation. Moreover, the mechanical properties are varied by varying the number of layers in hybrid composites. The hybrid composites with four layers of glass and three layers of banana (i.e. G4B3) are showing higher tensile, flexural and impact properties compared to G3B2 composites. Also, by varying orientation of banana fiber woven mat, the maximum mechanical properties obtained for composites containing G4B3 layering pattern at 0deg and 30deg orientations.