Glass Fiber Layers Research Articles

A paper and plastic device for performing recombinase polymerase amplification of HIV DNA.

Despite the importance of early diagnosis and treatment of HIV, only a small fraction of HIV-exposed infants in low- and middle-income countries are tested for the disease. The gold standard for early infant diagnosis, DNA PCR, requires resources that are unavailable in poor settings, and no point-of-care HIV DNA test is currently available. We have developed a device constructed of layers of paper, glass fiber, and plastic that is capable of performing isothermal, enzymatic amplification of HIV DNA. The device is inexpensive, small, light-weight, and easy to assemble. The device stores lyophilized enzymes, facilitates mixing of reaction components, and supports recombinase polymerase amplification in five steps of operation. Using commercially available lateral flow strips as a detection method, we demonstrate the ability of our device to amplify 10 copies of HIV DNA to detectable levels in 15 min. Our results suggest that our device, which is designed to be used after DNA extraction from dried-blood spots, may serve in conjunction with lateral flow strips as part of a point-of-care HIV DNA test to be used in low resource settings.

Effect of Water Absorption on Hardness Property for Epoxy Reinforced by Glass Fibers

This research includes studying the effect of water absorption on hardness properties for Epoxy reinforced with glass fibers .Composite materials prepared from the Epoxy resin as matrix reinforced by E-glass fibers [0 - 90o Woven Roving and Random ] with volume fraction 25%.The shore D hardness of all samples investigated before and after immersion in water at room temperature . Results of the work show that the value of hardness which done at room temperature decreases with increasing the time of immersion in water . The weight of absorbed water increases with increasing the time of immersion in water specially in the first week .The quantity of absorbed water decreases or increases also according to kind and number of reinforcing layers of glass fiber

Numerical Evaluation of Stiffness and Energy Absorption of a Hybrid Unidirectional/Random Glass Fiber Composite

A finite element method is employed to numerically evaluate the stiffness and energy absorption properties of an architecturally hybrid composite material consisting of unidirectional and random glass fiber layers. An ls-dyna finite element model of a composite hollow square tube is developed in which the position of the random fiber layers varies through the thickness. The assessment of the stiffness and energy absorption is performed via three-point impact and longitudinal crash tests at two speeds, 15.6 m/s (35 mph) and 29.0 m/s (65 mph), and five strain rates, ɛ· = 0.1 s−1, 1 s−1, 10 s−1, 20 s−1, and 40 s−1. It is suggested that strategic positioning of the random fiber microstructural architecture into the hybrid composite increases its specific absorption energy and, therefore, enhances its crashworthiness. The simulation data indicate that the composite structure with outer layers of unidirectional lamina followed by random fiber layers is the stiffest due to the considerable superior specific energy absorption of the random fiber micro-architecture. Moreover, it is illustrated that the specific energy absorption increases with the increased ratio of impact contact area over cross-section area. Of all the parameters tested the thickness of the unidirectional laminate on the specific energy absorption does not appear to have a significant effect at the studied thickness ratios.

Flowability of unidirectionally arrayed chopped strands in compression molding

This paper investigates the flowability of unidirectionally arrayed chopped strands (UACS) in compression molding of flat plates and rib structures. UACS is made by introducing regular slits into a unidirectional prepreg of carbon fiber. The stack of UACS plies is then cured into a laminate. To visualize the movement of the chopped strands, a UACS ply consisting of carbon fiber is inserted between glass-fiber plies. After molding, the glass-fiber layers become translucent, and the carbon-fiber chopped strands look black. This result reveals that the chopped strands are not only stretched in the transverse-fiber direction but are also moved in the fiber direction, following the extension of other layers. Furthermore, the interlayers slip easily, preventing direct contact between chopped strands during the formation of complex shapes. This demonstrates the excellent flowability of the UACS laminate even in high-volume-fraction fiber such as 60% where sheet molding compound (SMC) cannot flow smoothly.

Delamination detection and impact damage assessment of GLARE by active thermography

GLAss REinforced (GLARE) is a fibre metal laminate (FML) consisting of alternating layers of thin aluminium and glass fibre reinforced prepregs, whose improved physical properties confer it an interesting advantage over aluminium and composite materials for a number of aerospace applications. On the other hand, contrary to monolithic structures, GLARE can suffer from internal damage either during fabrication or in-serve stages. Non-destructive testing and evaluation (NDT&E) of GLARE is still a challenge, especially considering that large structures are typically sought (e.g., aircraft fuselage). In this paper, we investigated the use of infrared thermography for the inspection of GLARE. The experimental results presented herein demonstrate that it is possible to detect delamination-type defects and to assess the impact severity on GLARE through active thermography techniques, specifically pulsed thermography and vibrothermography. C-scan ultrasonic testing was performed as well with the intention of providing supplementary results.

Caractérisation du comportement mécanique d'un composite (tissu de verre/résine époxyde) à différentes périodes de vieillissement hygrothermiques

Characterization of the mechanical behaviour of composite (woven fabric glass/epoxy resin) at different times during hygrothermal ageing This paper considers the analysis of the mechanical behaviour of a laminate constituted of 12 layers of glass fiber fabric/epoxy resin conditioned at different relative humidities of 0, 60 and 96 % at 60 °C. The analysing of the experimental results obtained of hygrothermal ageing on the mechanical response has permited to show that the influence of the moisture concentration on the ultimate mechanical properties becomes significant and important for the composite conditioned at relative humidity of 96 % to the periods I and II (state of saturation and ageing) .

Mechanical Response of Laminate (Glass/Epoxy) at Different Periods of Environmental Conditioning (Saturation and Ageing)

This paper considers the analysis of the mechanical behaviour of a laminate constituted of 12 layers of glass fiber fabric/epoxy resin conditioned at different relative humidities of 0, 60 and 96% at 60 °C. The analysing of the experimental results obtained of hygrothermal ageing on the mechanical response has permited to show that the influence of the moisture concentration on the ultimate mechanical properties becomes significant and important for the composite conditioned at relative humidity of 96% to the periods I and II (state of saturation and ageing).

Marginal Adaptation and Fracture Resistance of Root-canal Treated Mandibular Molars with Intracoronal Restorations: Effect of Thermocycling and Mechanical Loading

This study evaluated the marginal adaptation, fracture modes, and loads to failure of different mesio-occlusal- distal (MOD) restorations in root canal treated molars in vitro. Forty mandibular first molars were randomly assigned to five groups (n = 8): UTR= untreated, RCT-AM= root-canal treated (RCT)+amalgam filling; RCT-COM= RCT+direct composite resin restoration; RCTFRC= RCT+composite resin restoration with two layers of multidirectional woven glass fibers; RCT-CER= RCT+ceramic inlay. All teeth were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49 N, 1.7 Hz, 3000 temperature cycles of 5°C to 50°C). Marginal adaptation was evaluated before and after TCML by scanning electron microscopy at 200X at the tooth/restoration interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5 mm/min. Failure types were analyzed and scored (reparable: modes 1 and 2; catastrophic: modes 3 to 5). Data were analyzed with ANOVA and Bonferroni correction. Marginal adaptation decreased significantly after TCML in all groups. The highest decrease was observed in RCT-FRC (before: 89.9 ± 2.2%, after TCML: 49.8 ± 11.9%) and the lowest in RCT-CER (before TCML: 90.3 ± 2.6% after TCML 80.4 ± 9.0%). Loads to failure (in N) were in descending order as follows: UTR: 3048 ± 905; RCT-CER: 1853 ± 477; RCT-AM: 1447 ± 363; RCT-FRC: 1066 ± 306; RCT-COM 960 ± 228. While UTR resulted in statistically higher loads to failure than those of all other groups (p < 0.0001), RCT-CER showed significantly higher results than those of RCT-COM (p = 0.0014) and RCT-FRC (p = 0.0042). The UTR group showed exclusively reparable failures in the form of either superficial (mode 1) or complete cusp chipping (mode 2), but all restored teeth exhibited catastrophic failures involving fractures along or through the restoration (modes 3 to 5). None of the restored teeth in any group were able to bear the same load level as the natural teeth. With regard to marginal adaptation and fracture resistance, luted ceramic inlays were advantageous. The integration of FRC in the restoration had no positive effect on the fracture resistance. FRC application showed a negative effect on marginal adaptation of composite resin restorations.

Marginal quality and fracture strength of root-canal treated mandibular molars with overlay restorations after thermocycling and mechanical loading.

To evaluate marginal quality, fracture modes, and loads-to-failure of different overlay restorations in rootcanal treated molars in a laboratory setup. Thirty-two mandibular first molars were randomly assigned to four groups (n = 8): UTR= untreated (control), RCT-COM= root canal treated (RCT)+ lab-made composite overlay, RCT-FRC= RCT+composite resin overlay with two layers of multidirectional woven glass fibers; RCT-CER: RCT+ceramic overlay. The teeth in all groups were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49 N, 1.7 Hz, 3000 temperature cycles of 5°C to 50°C). Marginal adaptation was evaluated before and after TCML with scanning electron microscopy at 200X at the tooth-to-luting composite (IF1) and luting composite-to restoration (IF2) interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5 mm/min. Data were analyzed with ANOVA and Bonferroni correction. Marginal adaptation decreased from 93 ± 3.4 to 82 ± 6.5 % at IF1 after TCML (p > 0.001) but the decrease was not significant between the groups (p = 0.8130). At IF2, ceramic overlays showed about 10% lower marginal adaptation than composite overlays (p < 0.0001). Loads-to-failure (in N) were as follows in descending order: RCT-FRC: 3619 ± 520; UTR: 3048 ± 905; RCT-COM: 2770 ± 457; RCT-CER 2036 ± 319. RCT-FRC showed significantly higher results than those of RCT-COM (p = 0.0077) and RCT-CER (p < 0.0001). Only RCT-CER showed significantly lower results than that of the control (p = 0.0019). While the fractures in the UTR occurred exclusively above the cementoenamel junction (Mode 1 and Mode 2) and were rated reparable, RCT-COM and RCT-CER showed exclusively catastrophic failures in varying modes (nodes 3 to 5). Only in group RCT-FRC, half of the specimens fractured in a reparable fracture mode (modes 1 and 2) with veneering composite delamination from the glass-fiber weaver layer. As cusp-covering overlay restorations in root canal treated molars, composite resin overlays with and without fiber reinforcement performed similar to intact teeth with varying failure types. While intact teeth failed exclusively in reparable modes, all other restorations failed in a catastrophic manner, except half of the fiber reinforced composite group.

Environmental durability of a CFRP system for strengthening steel structures

Recently a high modulus CFRP system was developed to enhance the load carrying capacity and serviceability of steel bridges and structures. However, the environmental durability of the system has not yet been demonstrated. This paper presents the findings of a research program that was conducted to evaluate the environmental durability of the bond of the proposed CFRP strengthening system to steel surfaces. The program consisted of testing 44 steel-CFRP double-lap shear specimens. The specimens were exposed to severe environmental conditions for different durations, up to 6 months. Different methods to enhance the bond durability were studied including pre-treating the steel surface with a silane coupling agent, inserting a glass fiber layer within the adhesive and a combination of both methods of protection. The research findings indicate that the use of a silane coupling agent significantly enhanced the bond durability. While the presence of the glass fibers helped to enhance the initial bond strength of the system, it did not improve the durability of the bond. The use of both techniques enhanced both the overall bond strength and the environmental durability of the strengthening system.

Quantitative thermoelastic measurement on a helicopter glass fibre component underneath a surface anti-fretting coating.

Thermoelastic stress analysis (TSA) has been applied to measure the first stress invariant on a composite helicopter component under load. The component comprised inner mono-directional glass fiber layers with an outer central plate in glass fiber cloth, covered by an anti-fretting surface coating. In order to obtain quantitative results, a previous calibration of the thermoelastic constant obtained on a composite sample with a similar anti-fretting coating has been necessary.

Modification of Glass Fiber-Reinforced Epoxy with Amine Functional Aniline Formaldehyde Condensate (AFAFC)

Unmodified epoxy glass fiber laminates are brittle by nature. In this study, an improvement of the mechanical properties, such as impact, tensile and flexural strengths of the reinforced glass fiber diglycidyl ether of bisphenol-A based epoxy laminate, was carried out by incorporating an amine functional aniline formaldehyde condensate (AFAFC) modifier. AFAFC was synthesized by reacting aniline and formaldehyde in an acid medium (pH 4) and was characterized by FT-IR and 1-H NMR spectroscopy, viscosity measurements, elemental analysis and potentiometric titration. The fracture energies of the modified glass fiber composite were vastly improved and the improvement depended on the concentration of the modifier. The optimum properties were obtained by adding 10 phr (parts per hundred parts of epoxy resin) of the modifier. Furthermore, the fracture energies of the modified glass fiber composite increased with increasing the number of glass fiber layers. Scanning electron microscopy showed that round shaped AFAFC oligomer domains were formed in the matrix. These oligomer domains led to improved strength and toughness due mainly to the 'rubber toughening' effect in the brittle epoxy matrix. The thermal stability of the modified epoxy composites by thermogravimetric analysis was also reported.

Identification method of structural defects in glass fiber fabric/epoxy resin laminate

We present the experimental methods proposed for the identification of structural defects of the laminate constituted of 12 layers of glass fiber fabric/epoxy resin. Two techniques of control were used to analyze the principal structural defects (local or global disorientation). The first technique provides a superficial observation (macroscopic analysis) of the superior and lower surfaces of each layer, while the second one ensures internal observation (microscopic analysis) of different layers after pyrolysis of the matrix (delamination of the laminate).

Cyclic Behavior of RC Columns Strengthened by FRP and Steel Devices

This paper presents several results of a wide experimental program undertaken to evaluate the seismic performance of RC columns, externally confined with fiber-reinforced polymers (FRPs). Specimens consisted of full scale square columns, 300 mm on each side, reinforced by using both smooth and deformed steel rebars and subjected to a constant axial load and monotonic or cyclic flexure; in particular, two levels of the axial load were considered. Tests were conducted, in displacement control, on both FRP confined and unconfined RC columns: the confinement system was obtained by partially wrapping two or four unidirectional carbon (CFRP) or glass (GFRP) fiber layers around the member; additionally, some tests were performed on members strengthened by using both the external CFRP wrapping and longitudinal steel angles. Experimental results allowed evaluating depending on the level of applied axial load and on the type of steel rebars adopted for reinforcing each column—the benefits introduced by the considered strengthening systems in terms of strength, ductility, and energy dissipation capacity.

Nano-structured sandwich composites response to low-velocity impact

Abstract This paper investigates the influence of exfoliated nano-structures on sandwich composites under impact loadings. A set of sandwich composites plates made of fiberglass/nano-modified epoxy face sheets and polystyrene foams was prepared. The core was 25 mm thick and the face sheets were made of eight layers of woven fabric glass fibers and nano-modified epoxy (≈0.8 mm of thickness). The epoxy system was bisphenol A resin and an amine hardener. The fiber volume fraction used was around 65%, while the nanoclay content varied from 0 wt.% to 10 wt.%. The nanoclay used was Cloisite 30B from Southern Clay. The sandwich panels were submitted to low-velocity impact tests with energies from 5 J to 75 J. Two sets of experiments were performed, i.e. high velocity + low mass and low velocity + high mass. Damage caused by the two groups of experiments and peak forces measured were dissimilar. The results show that the addition of 5 wt.% of nanoclay lead to a more efficient energy absorption. The failure modes were also analyzed, and they seems to be affected by the nanoclay addition to face sheets.

Grinding wheel with grains of different sizes

Improvement of grinding by ensuring uniform abrasive action on the surface of the part over the whole height of the grinding wheel is considered. The use of a flat abrasive wheel with bands of different grain size is proposed; the bands are reinforced by layers of glassfiber or other material. From the frontal strip, the grain size declines over the whole height of the wheel. A method of calculating the mean grain size for each band is outlined.

Enhanced Degree of Monomer Conversion of Orthodontic Adhesives Using a Glass-Fiber Layer under the Bracket

To test the hypothesis that there is no difference in the degree of conversion (DC%) of orthodontic composites during the light-curing process with or without the use of a glass-fiber reinforcement. Two light-curing orthodontic adhesives, Transbond XT (TB) and Beauty Ortho Bond (BO), were used with woven preimpregnated glass fibers. The degree of monomer conversion was determined for both adhesives in three settings (n = 5 per group): in the first group, the adhesive was cured without a bracket (control); in the second group, the bracket was bonded using adhesive without fiber reinforcement; and in the third group, a layer of glass-fiber net was added between the bracket and resin. The adhesive resin was light cured, and the DC% was determined by Fourier transform infrared spectroscopy. A two-way analysis of variance revealed significant differences in the DC% (P < .001) between adhesives and between the fiber-reinforced and nonreinforced groups. When the nonreinforced adhesives were light cured under the brackets, the DC% was significantly lower (TB: 37.0%, SD 3.4; BO: 36.9%, SD 1.9) compared with the control (TB: 54.7%, SD 0.6; BO: 65.9%, SD 0.5). A higher DC% was found when the resin was light cured in the presence of a glass-fiber net (TB: 44.1%, SD 0.3; BO: 55.3%, SD 1.7). The hypothesis is rejected. The degree of monomer conversion of the light-curing adhesive resin under stainless steel bracket can be improved by adding a thin layer of glass-fiber-reinforced composite between the bracket and adhesive resin.

Post-impact damage characterization of hybrid configurations of jute/glass polyester laminates using acoustic emission and IR thermography

In this work, residual post-impact properties of two configurations of E-glass/jute hybrid laminates are characterized, both manufactured using a total fibre volume of 50 ± 2% (14 glass fibre layers + 4 jute fibre layers). T-laminates included a core obtained by multiple layers of jute between two E-glass fibre reinforced skins, whilst in Q-laminates single layers of jute fibres were intercalated at different levels between E-glass fibre reinforced layers. All laminates were impacted at five levels of energy, from 5 to 15 J, and then subjected to post-impact flexural tests. The results suggest that T hybrids perform better at low impact energies (up to 10 J), which do not damage significantly the laminate core. In contrast, Q hybrids are better suited to withstand extensive damage produced by higher impact energies (12.5 and 15 J), in that they allow a more effective redistribution of impact damage in the structure. This was confirmed by acoustic emission (AE) monitoring during flexural loading, which offered indications on the maximum stress laminates can undergo after impact damage. Pulse IR thermography yielded information on their mode of failure by visualizing impact-damaged areas.

Enhanced Degree of Monomer Conversion of Orthodontic Adhesives Using a Glass-Fiber Layer under the Bracket

Enhanced Degree of Monomer Conversion of Orthodontic Adhesives Using a Glass-Fiber Layer under the Bracket

Mechanical properties and water sorption behavior of phenol–formaldehyde hybrid composites reinforced with banana fiber and glass fiber

AbstractBanana fiber, which is rich in cellulose, relatively inexpensive, and abundantly available, has potential for polymer reinforcement. This study explores the merits of combining high‐modulus glass fibers with banana fiber in phenolic resoles to develop high‐performance, cost‐effective, lightweight hybrid composites. Of particular interest is the effect of varying layering patterns of banana fiber and glass fiber on the tensile, flexural, and impact properties of hybrid composites. The highest tensile strength value has been obtained for an intimate mixture of both fibers, and the maximum flexural and impact strength has been obtained for composite samples prepared from interleaving layers of banana fiber and glass fiber. Tensile, flexural, and impact properties of the composites increase with an increasing volume fraction of glass fiber. The water uptake of these composites decreases with the incorporation of glass fiber into banana fiber, and the composites with glass fiber at the periphery and banana fiber at the core have the maximum resistance to water absorption. Scanning electron micrographs show the fracture mechanism and fiber/matrix adhesion in these composites © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008