Glass Mat Research Articles

Hybrid epoxy nanocomposites: lightweight materials for structural applications

The processing parameters, namely, clay loading, magnetic stirring time and sonication time, were optimized for the dispersion of two types of clay into an epoxy and into chopped strand mat (CSM) glass fiber-based epoxy nanocomposite laminates. A vacuum-assisted resin transfer molding setup was used to fabricate these laminates. Optimizations were performed based on improvements in Young's modulus. The intercalated and exfoliated distributions of clay in the composites were confirmed using X-ray diffraction and transmission electron microscopy. The transmission electron micrographs of optimized specimens showed a well-ordered intercalated structure within the epoxy. Using optimized processing conditions, three layered laminates of CSM, woven roving glass fibers or both were prepared with epoxy and clay for the preparation of new lightweight hybrid epoxy nanocomposites. The tensile, flexural and impact properties of these hybrid nanocomposites were investigated. A combination of the two types of glass fibers produced promising results. Transmission electron microscopy of epoxy nanocomposites with process parameters of clay loading of 2.0 wt%, magnetic stirring time of 120 min and sonication time of 30 min showed good intercalation morphology. The glass fiber-based composites containing epoxy and clay mixture with these parameters produced maximum Young's modulus.

Структурные характеристики абсорбтивно-стеклянных сепараторов и их влияние на эффективность ионизации кислорода в макетах свинцово-кислотных аккумуляторов

The most important structural and physicomechanical properties of absorbent glass mat separators «Hollingswoth and Vose», «Bernard Dumas», «BMSK AT Nippon» intended for lead-acid battery (LAB) are studied. It is shown that on pore size distribution strong influence puts the enclosed pressure: at compression 50 kPa there is a considerable reduction of the size of a pore. However for the separation material «BMSK AT Nippon» the share of pores with radius from 5 to 10 microns is much higher, than for the separation materials «Hollingswoth and Vose» and «Bernard Dumas». Studying of process of oxygen absorption on negative an electrode in the LAB models showed that most effectively process of absorption of oxygen occurs in the LAB models to the separation material «BMSK AT Nippon».

PREPARATION OF ANTIBACTERIAL POLYESTER GLASS MAT SHEETS CONTAINING PDMAEMA-FUNCTIONALIZED MWNT NANOCOMPOSITES

Antibacterial glass mat sheets containing unsaturated polyester resin as a matrix and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA)-functionalized multi-walled carbon nanotube (MWNT) nanocomposites as a filler were prepared. Controlled functionalization of MWNT by in situ atom transfer radical polymerization (ATRP) of DMAEMA was applied for the preparation of nanocomposites. An antibacterial activity of the prepared unsaturated polyester glass mat sheets was determined by the application of film contact method based on the Japanese Industrial Standard JIS Z-2801. The mechanical properties of the prepared unsaturated polyester glass mat sheets were estimated by the simplified procedure designed in laboratory. A deliberate search for the ATRP process conditions showing the most effective antibacterial activity was tried beyond all experiments.

Glass-fibre reinforced composite materials based on unsaturated polyester resins

The effect of glass-fibre content on the thermal and mechanical properties of cross-linked composites based on unsaturated polyester resins have been investigated by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and by measuring the heat distortion temperature (HDT). Two different matrix resins and two different glass mats were used, and the glass-fibre contents varied. Altogether 12 composite systems were tested. The glass- transition temperature of each composite was characteristic to the matrix resin and did not depend on the glass-fibre content, as it was expected. The effect of glass-fibre content on the storage modulus and on HDT has been elucidated. It has been found that up to 12 mass% (6 vol%) glass-fibre content the HDT did not change, above this value it increased with increasing glass-fibre content for each composite, but not at the same extent. This means that matrix-fibre interaction has an important role in the performance of the composites at elevated temperatures. Storage moduli increased with increasing glass-fibre content. The temperatures detected by dynamic mechanical thermal analysis corresponding to the storage modulus of 750 MPa—calculated by Takemori—are above the glass-transition and also increased with higher glass-fibre content in accordance with the real heat-distortion temperature measurements. It may be concluded that the effect of reinforcement on the performance of the composite could be detected more reliably by HDT measurements, since it gives information on the deformation of the composites. Matrix-fibre interaction has an essential role on the performance and on the HDT of the composite materials.

Comparison of tensile properties and impact damage tolerance of hemp and glass fiber composites

Tensile properties and impact damage tolerance of hemp fiber and chopped strand mat (CSM) glass fiber composites have been evaluated and compared. The absolute and specific tensile properties of CSM glass fiber composites were found to be much superior to hemp fiber composites. Impact damage tolerance of hemp fiber composites was also quite low compared to CSM glass fiber composites. They lost almost half of their intrinsic strength and stiffness following an impact of 2 J energy. Considerable evidence of matrix fracture, interfacial debonding, and fiber fracture was found in the fracture surface. Following an impact at 4 J energy, hemp fiber composites lost almost 70% of their intrinsic strength and stiffness. In comparison, CSM glass fiber composites were able to endure an impact of 20 J energy for 70% reduction in their intrinsic strength and stiffness.

Microscopic resolution broadband dielectric spectroscopy

Results are presented for a non-contact measurement system capable of micron level spatial resolution. It utilises the novel electric potential sensor (EPS) technology, invented at Sussex, to image the electric field above a simple composite dielectric material. EP sensors may be regarded as analogous to a magnetometer and require no adjustments or offsets during either setup or use. The sample consists of a standard glass/epoxy FR4 circuit board, with linear defects machined into the surface by a PCB milling machine. The sample is excited with an a.c. signal over a range of frequencies from 10 kHz to 10 MHz, from the reverse side, by placing it on a conducting sheet connected to the source. The single sensor is raster scanned over the surface at a constant working distance, consistent with the spatial resolution, in order to build up an image of the electric field, with respect to the reference potential. The results demonstrate that both the surface defects and the internal dielectric variations within the composite may be imaged in this way, with good contrast being observed between the glass mat and the epoxy resin.

Integrated photocatalytic-biological reactor for accelerated 2,4,6-trichlorophenol degradation and mineralization

An integrated photocatalytic-biological reactor (IPBR) was used for accelerated degradation and mineralization of 2,4,6-trichlorophenol (TCP) through simultaneous, intimate coupling of photocatalysis and biodegradation in one reactor. Intimate coupling was realized by circulating the IPBR's liquid contents between a TiO(2) film on mat glass illuminated by UV light and honeycomb ceramics as biofilm carriers. Three protocols-photocatalysis alone (P), biodegradation alone (B), and integrated photocatalysis and biodegradation (photobiodegradation, P&B)-were used for degradation of different initial TCP concentrations. Intimately coupled P&B also was compared with sequential P and B. TCP removal by intimately coupled P&B was faster than that by P and B alone or sequentially coupled P and B. Because photocatalysis relieved TCP inhibition to biodegradation by decreasing its concentration, TCP biodegradation could become more important over the full batch P&B experiments. When phenol, an easy biodegradable compounds, was added to TCP in order to promote TCP mineralization by means of secondary utilization, P&B was superior to P and B in terms of mineralization of TCP, giving 95% removal of chemical oxygen demand. Cl(-) was only partially released during P experiments (24%), and this corresponded to its poor mineralization in P experiments (32%). Thus, intimately coupled P&B in the IPBR made it possible obtain the best features of each: rapid photocatalytic transformation in parallel with mineralization of photocatalytic products.

Gelled electrolytes for use in absorptive glass mat valve-regulated lead-acid (AGM VRLA) batteries working under 100% depth of discharge conditions

Gelled electrolytes prepared from fumed silica for use in absorptive glass mat valve-regulated lead-acid (AGM VRLA) batteries and the effect of veratraldehyde addition on the electrochemical behavior and performance of AGM VRLA batteries are investigated. Cyclic voltammetry is used to investigate differences in the electrochemical behaviors of nongelled and gelled electrolytes and between gelled electrolytes with and without veratraldehyde. Battery performance is tested under 100% depth of discharge (100% DoD) conditions at both low- (0.1C) and high- (1C) rate discharges. The addition of silica or veratraldehyde does not affect the main reaction of the lead-acid batteries but tends to suppress the hydrogen evolution reaction. AGM VRLA batteries with gelled electrolytes have a higher discharge capacity and longer cycle life than the conventional nongel AGM VRLA batteries. The addition of 0.005% (w/v) veratraldehyde further improves battery performance, but higher (0.01%, w/v) veratraldehyde concentrations reduce it and correlate with the enhanced growth of lead sulfate crystals. The AGM VRLA battery prepared from a gelled electrolyte containing 0.005% (w/v) veratraldehyde provides the best battery performance in every operating temperature studied (0–60°C).

PLLA/Flax Mat/Balsa Bio-Sandwich—Environmental Impact and Simplified Life Cycle Analysis

In the present paper the environmental impact of biocomposites and bio-sandwich materials production are evaluated, using simplified Life Cycle Analysis (LCA) following the procedure recommended in the ISO 14044 standard. The materials are dimensioned and evaluated by comparing with reference materials, glass mat reinforced unsatured polyester and glass mat/unsatured polyester/balsa sandwich. The results indicate that bio-sandwich materials are very attractive in terms environmental impact. However further improvements in biocomposite and bio-sandwich mechanical strength are necessary if they are to be used in transport application compared to glass/polyester and glass/polyester/balsa sandwich.

Formation of novel thermoplastic composites using bicomponent nonwovens as a precursor

This study focuses on a novel technique to produce thermoplastic composites directly from bicomponent nonwovens without using any resins or binders. Conceptually, the structure of the bicomponent fibers making up these nonwovens already mimics the fiber–matrix structure of fiber reinforced composites. Using this approach, we successfully produced isotropic thermoplastic composites with polymer combinations of polyethylene terephthalate/polyethylene (PET/PE), polyamide-6/polyethylene (PA6/PE), polyamide-6/polypropylene (PA6/PP), and PP/PE. The effects of processing temperature, fiber volume fraction, and thickness of the preform on the formation and structure of the nonwoven composites were discussed. Processing temperatures of 130 and 165 °C for PE and PP matrices, respectively, resulted in intact composite structures with fewer defects, for fiber volume fraction values of up to 51%. Moreover, an insight into the changes on the fine structure of the bicomponent fibers after processing was provided to better explain the mechanics behind the process. It is hypothesized that the composite fabrication process can result in annealing and increases the degree of crystallinity and melting temperature of polymers by thickening lamellae and/or removing imperfections. One of the other outcomes of this study is to establish what combination of mechanical properties (tensile and impact) nonwoven composites can offer. Our results showed that compared to glass mat reinforced thermoplastic composites, these novel isotropic nonwoven composites offer high specific strength (97 MPa/g cm−3 for PA6/PE), very high strain to failure (152% for PP/PE), and superior impact strength (147 kJ/m2 for PA6/PP) which can be desirable in many critical applications.

Non-linear Viscoelastic-Viscoplastic Constitutive Modelling of Creep in Continuous Fibre Glass Mat Thermoplastic Composites

Non-linear Viscoelastic-Viscoplastic Constitutive Modelling of Creep in Continuous Fibre Glass Mat Thermoplastic Composites

Glass–basalt/epoxy hybrid composites for marine applications

The aim of this work is to evaluate the influence of uniaxial basalt fabric layers on the mechanical performances of a glass mat/epoxy composite used for marine applications.Polymer composites, reinforced by glass mat (GFRP), and hybrid ones, reinforced by glass mat and unidirectional basalt fabric, have been produced by vacuum bagging technique. Three points bending and tensile tests have been carried out in order to evaluate the effect of number and position of basalt layers on the mechanical properties of the investigated structures.The experimental tests have showed that the presence of two external layers of basalt involves the highest increase in mechanical properties of hybrid laminates compared to those of GFRP laminates.In addition, a simplified numerical model has been proposed to better understand the influence of unidirectional basalt on the specific mechanical properties of the laminates. The correspondence between the predicted numerical results and the experiments proves the accuracy of this model, which has also been applied to a real ship component.

Morphology and mechanical properties of isotactic polypropylene glass mat thermoplastic composites modified with organophilic montmorillonite

Satisfactory impregnation of glass fiber mats may be obtained with isotactic polypropylene/montmorillonite (MMT) nanocomposites under conditions comparable with industrial conditions. However, it is demonstrated here that the high melt viscosity of the nanocomposite matrix at low shear rates may significantly influence the release of the compressive load in the glass mat and hence the glass fiber distribution in consolidated specimens. Thus, depending on the initial lay-up and overall glass fiber content, the bending modulus may either increase or decrease with increasing MMT content, whereas the tensile modulus is more consistent with micromechanical models assuming a uniform glass fiber distribution. Results from fractographic analyses show that the presence of matrix rich layers at the specimen surfaces may also lead to premature crack initiation and failure in flexion.

A field operational test on valve-regulated lead-acid absorbent-glass-mat batteries in micro-hybrid electric vehicles. Part I. Results based on kernel density estimation

In March 2007 the BMW Group has launched the micro-hybrid functions brake energy regeneration (BER) and automatic start and stop function (ASSF). Valve-regulated lead-acid (VRLA) batteries in absorbent glass mat (AGM) technology are applied in vehicles with micro-hybrid power system (MHPS). In both part I and part II of this publication vehicles with MHPS and AGM batteries are subject to a field operational test (FOT). Test vehicles with conventional power system (CPS) and flooded batteries were used as a reference. In the FOT sample batteries were mounted several times and electrically tested in the laboratory intermediately. Vehicle- and battery-related diagnosis data were read out for each test run and were matched with laboratory data in a data base. The FOT data were analyzed by the use of two-dimensional, nonparametric kernel estimation for clear data presentation.The data show that capacity loss in the MHPS is comparable to the CPS. However, the influence of mileage performance, which cannot be separated, suggests that battery stress is enhanced in the MHPS although a battery refresh function is applied. Anyway, the FOT demonstrates the unsuitability of flooded batteries for the MHPS because of high early capacity loss due to acid stratification and because of vanishing cranking performance due to increasing internal resistance. Furthermore, the lack of dynamic charge acceptance for high energy regeneration efficiency is illustrated. Under the presented FOT conditions charge acceptance of lead-acid (LA) batteries decreases to less than one third for about half of the sample batteries compared to new battery condition. In part II of this publication FOT data are presented by multiple regression analysis (Schaeck et al., submitted for publication [1]).

Wear characteristics of thermoset composite under high stress three-body abrasive

Three-body abrasive wear of chopped strand mat glass fibres reinforced polyester (CGRP) was studied for three principal orientations of the fibres, i.e. parallel orientation (P-O), anti-parallel orientation (AP-O) and normal orientation (N-O). The tests were carried out under high stress conditions. A correlation between the specific wear rate and mechanical properties was established. As a result, CGRP composite exhibited better wear characteristic in P-O than in AP-O and N-O. Different wear mechanisms were observed on the worn surfaces of the materials, including pitting, micro- and/or macro-cracks, as well as breakage and debonding of the fibres.

A field operational test on valve-regulated lead-acid absorbent-glass-mat batteries in micro-hybrid electric vehicles. Part II. Results based on multiple regression analysis and tear-down analysis

In the first part of this work [1] a field operational test (FOT) on micro-HEVs (hybrid electric vehicles) and conventional vehicles was introduced. Valve-regulated lead-acid (VRLA) batteries in absorbent glass mat (AGM) technology and flooded batteries were applied. The FOT data were analyzed by kernel density estimation. In this publication multiple regression analysis is applied to the same data. Square regression models without interdependencies are used. Hereby, capacity loss serves as dependent parameter and several battery-related and vehicle-related parameters as independent variables. Battery temperature is found to be the most critical parameter. It is proven that flooded batteries operated in the conventional power system (CPS) degrade faster than VRLA–AGM batteries in the micro-hybrid power system (MHPS).A smaller number of FOT batteries were applied in a vehicle-assigned test design where the test battery is repeatedly mounted in a unique test vehicle. Thus, vehicle category and specific driving profiles can be taken into account in multiple regression. Both parameters have only secondary influence on battery degradation, instead, extended vehicle rest time linked to low mileage performance is more serious.A tear-down analysis was accomplished for selected VRLA–AGM batteries operated in the MHPS. Clear indications are found that pSoC-operation with periodically fully charging the battery (refresh charging) does not result in sulphation of the negative electrode. Instead, the batteries show corrosion of the positive grids and weak adhesion of the positive active mass.

Lead-acid batteries in micro-hybrid applications. Part II. Test proposal

In the first part of this work [1] selected key parameters for applying lead-acid (LA) batteries in micro-hybrid power systems (MHPS) were investigated. Main results are integrated in an accelerated, comprehensive test proposal presented here. The test proposal aims at a realistic representation of the pSoC operation regime, which is described in Refs. [1,6]. The test is designed to be sensitive with respect to dynamic charge acceptance (DCA) at partially discharged state (critical for regenerative braking) and the internal resistance at high-rate discharge (critical for idling stop applications). First results are presented for up-to-date valve-regulated LA batteries with absorbent glass mat (AGM) separators. The batteries are close to the limits of the first proposal of pass/fail-criteria. Also flooded batteries were tested; the first out of ten units failed already.

Lead-acid batteries in micro-hybrid applications. Part I. Selected key parameters

Micro-hybrid electric vehicles were launched by BMW in March 2007. These are equipped with brake energy regeneration (BER) and the automatic start and stop function (ASSF) of the internal combustion engine. These functions are based on common 14 V series components and lead-acid (LA) batteries. The novelty is given by the intelligent onboard energy management, which upgrades the conventional electric system to the micro-hybrid power system (MHPS). In part I of this publication the key factors for the operation of LA batteries in the MHPS are discussed. Especially for BER one is high dynamic charge acceptance (DCA) for effective boost charging. Vehicle rest time is identified as a particular negative parameter for DCA. It can be refreshed by regular fully charging at elevated charge voltage. Thus, the batteries have to be outstandingly robust against overcharge and water loss. This can be accomplished for valve-regulated lead-acid (VRLA) batteries at least if they are mounted in the trunk. ASSF goes along with frequent high-rate loads for warm cranking. The internal resistance determines the drop of the power net voltage during cranking and is preferably low for reasons of power net stability even after years of operation. Investigations have to be done with aged 90 Ah VRLA–absorbent glass mat (AGM) batteries. Battery operation at partial state-of-charge gives a higher risk of deep discharging (overdischarging). Subsequent re-charging then is likely to lead to the formation of micro-short circuits in the absorbent glass mat separator.

Preparation and Physico-Chemical Study of Sandwich Glass-Jute-Bisphenol-C-Formaldehyde Resin Composites

Glass-Jute-bisphenol-C-formaldehyde (Glass-Jute-BCF) sandwich composites were prepared by hand lay-up technique at 150°C under 30.4 MPa pressure for 2 h. The resin, glass and jute fiber content in the sandwich composite were 33.3, 10.4 and 56.3 wt%, respectively. 10 prepregs containing 8 inner prepregs of jute mats sandwiched between 2 outer prepregs of glass mats. Glass-Jute-BCF sandwich composite has 23 MPa tensile strength, 119 MPa flexural strength, 1.72 kV/mm electric strength and 1.25 × 1012 ohm cm volume resistivity. Tensile strength and volume resistivity both decreased, while flexural strength and electrical strength both improved upon hybridization. Sandwich composite showed high diffusivity in water, 10% NaCl and 10% HCl solutions as compared to Glass-BCF composite. Equilibrium water absorption time is found to be 72 h in all 3 environments. Comparatively low diffusivity is observed due to silane treated glass fibers. No effect of boiling water is observed on stability of composite. Saturation time in boiling water reduced 18 times without any damage to the composite. Glass-Jute-BCF sandwich composite may be useful for low load bearing applications in construction, electrical and electronic industries as well as in harsh acidic and saline environments.

Simulation of Car Bumper Material using Finite Element Analysis

Bumper is one of the main parts which are used as protection for passengers from front and rear collision. The aim of this study was to analyze and study the structure and material employed for car bumper in one of the national car manufacturer. In this study, the most important variables like material, structures, shapes and impact conditions are studied for analysis of the bumper beam in order to improve the crashworthiness during collision. The simulation of a bumper is characterized by impact modelling using Abaqus 6.9 according to the speed that is 13.3 m sec-1 (48 km h-1) given in order to analyse the results. This speed is according to regulations of Federal Motor Vehicle Safety Standards, FMVSS 208- Occupant Crash Protection whereby the purpose and scope of this standard specifies requirements to afford impact protection for passengers. In this research, the three types of material were selected that are relevant to be applied to the front bumper beam. The materials consist of Expanded Polypropylene (EPP), Glass Mat Thermoplastics (GMT) and Sheet Molding Compound (SMC). These materials were studied by impact modelling to determine the kinetic energy, potential energy and strain energy. The selected materials are compared to each other to find the best material with highest material strength and structure. Simulation using Finite Element Analysis software, which is ABAQUS was conducted. The results showed that a modified SMC bumper can reduce the impact of collision with higher performance and was suggested to replace GMT and EPP. The duration taken for SMC to deflect the impact was the shortest compared to GMT and EPP The findings also showed that EPP cannot totally absorb the energy and reduce the impact of collision.