Glass Fabric Composites Research Articles

Contrast enhancement in visualisation of woven composite tow architecture using a MicroCT Scanner. Part 1: Fabric coating and resin additives

MicroCT scanning is a non-destructive inspection method which was used to visualise tow architecture in woven composites with the ultimate goal of three-dimensional model generation. This has been achieved in the past for glass fabric composites, but is problematic when applied to carbon fabrics. Using X-rays, it is difficult to discriminate between elements of the composite, particularly the region between co-aligned neighbouring tows. This presents difficulty when viewing such composites using X-ray MicroCT scanning. Additives were used to enhance contrast during scanning. The most successful techniques were coating of fabrics with gold, copper, and an iodine contrast agent. Resin particle additive techniques were also trialled, with limited success. Good visualisations of glass fabrics were possible without contrast enhancement. Three-dimensional reconstructions of interior tow architectures were then made from the scans of contrast enhanced specimens. This research can be viewed as a starting point in developing methods for generating contrast between neighbouring tows within a three-dimensional woven preform using MicroCT scanning.

Mechanical Properties of Coir/Glass Fiber Phenolic Resin Based Composites

Phenolic resin based coir/glass hybrid composites were developed using compression molding followed by hand lay-up technique. Mechanical properties such as tensile and flexural properties of coir based hybrid composites were investigated as a function of fiber content and fiber volume fraction. This study is focused on the mechanical performance of coir based and its hybrid composites. Results showed that tensile properties increase with increasing fiber content. Mechanical properties of composites with increased glass fiber content have high values. The effect of alkali-treatment of fibers on the mechanical properties was also studied. Significant improvement in coir based composites by alkali-treatment was observed. Overall studies indicated that the short coir/ glass fabric hybrid polyester composites are promising candidates for structural applications where high strength and stiffness is required.

Nondestructive Evaluation of Anisotropy in Composite Materials Via Acoustic Birefringence

A linearly polarized ultrasonic shear wave propagating in fiber-reinforced composites produces an elliptical vibration pattern due to birefringence. The acoustic birefringence of shear waves is analyzed and applied for evaluation of in-plane stiffness anisotropy of uni-axial nonfabric, biaxial, and quadra-axial fabric composite materials. The parameters of the elliptical motion are determined by measurements of the amplitude and phase of the transmitted/reflected shear wave as functions of the receiver polarization angle. The strength of birefringence is derived from the measured elliptical pattern and used to quantify the in-plane stiffness asymmetry in glass and carbon fiber-reinforced nonfabric and fabric composites. The technique is shown to be sensitive enough to detect damage induced variation in stiffness anisotropy. The correlation between the asymmetry of shear stiffness and orientation of impact cracking in composites is also discussed.

An Analysis of Aging Characteristics of Tilting Train under Accelerated Aging Environment

In this study, the effect of combined environmental factors such as ultraviolet ray, high temperature and high moisture on mechanical and thermal analysis properties of glass fabric and phenolic composites are evaluated through a 2.5KW accelerated environmental aging tester. The environmental factors such as temperature, moisture and ultraviolet ray applied of specimens. A xenon-arc lamp is utilized for ultraviolet light and exposure time of up to 3000 hours are applied. Several types of specimens - tensile, bending, and shear specimens that are warp direction and fill direction are used to investigate the effects of environmental factors on mechanical properties of the composites. Mechanical degradations for tensile, bending and shear properties are evaluated through a Universal Testing Machine (UTM). Also, storage shear modulus, loss shear modulus and tan δ are measured as a function of exposure time through a Dynamic Mechanical Analyzer (DMA). From the experimental results, changes in material properties of glass fabric and phenolic composites are shown to be slightly degraded due to combined environmental effects.

Leakage characteristics of the glass fabric composite barriers of LNG ships

Abstract The consumption of LNG (Liquefied Natural Gas) has recently increased due to a substantial rise in the price of petroleum. One of the major carriers of LNG is the LNG ships whose containment systems are composed of corrugated stainless steel plates (primary barriers) and glass fabric composite sandwich constructions (secondary barriers). The primary barriers are constructed by welding many corrugated thin stainless steel plates to reduce thermal stress, while the secondary barriers are constructed by adhesively bonding glass fabric composite sandwich constructions. One of the key technologies for the secondary barriers is to thoroughly seal the adhesive joining area, which can retard LNG leakage when the primary barriers are failed. The sealing quality of the adhesive joint is dependent on the wetting characteristics between the sandwich constructions and adhesive, which is in turn dependent on the curing cycle for the adhesive. In this work, a new method to measure the gas leakage of adhesively bonded joint was devised. The adhesive joint specimens were prepared under several different curing cycles to investigate the impregnation of adhesive into the glass fabric composite. Also, the thermal residual stress in the adhesive joint was estimated by the double strip deformation experiment. Finally, an improved curing method was developed with high tightness of the secondary barriers without increase of thermal residual stress.

The effects of curing cycles on properties of the epoxy system 3221/RH glass fabric composites

AbstractIn this work, the epoxy system 3221 and its glass fabric laminates were thermally cured under different curing temperatures. The curing degree of the resin was increased with elevated reaction temperature. Dynamic mechanical analysis was performed on the laminate coupons and glass transition temperature (Tg) and relative stiffness (E′) of composites were measured before and after soaked in distilled water at 70°C. A shift in glass transition temperature to higher values and the splitting of the tan δ curve were observed with extent of cure under dry conditions. Tg values shifted to lower temperatures after immersion. Under wet condition, the change in Tg1 was very small when the curing degree was up to 96%. The relative stiffness experienced a reduction both in initial modulus and the initial sharp drop temperature after immersion. It also suggested that the excessively high curing temperature (>130°C) had a negative effect on the retention of relative stiffness under wet condition. Both the interlaminar shear strength and dielectric properties of laminates were determined before and after immersion. The compared results demonstrated that the elevated curing temperature played a good influence on both of the properties before aged. However, for samples cured above 130°C, lower retention of interlaminar shear strength and poor dielectric properties were observed during immersion due to their higher moisture contents. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Mechanical Behavior of Isothalic Polyester-based Untreated Woven Jute and Glass Fabric Hybrid Composites

In this study, the effect of hybridization on mechanical properties of untreated (as received) woven jute and glass fabric-reinforced isothalic polyester composites has been evaluated experimentally. Hybrid laminates are fabricated using hand lay-up technique. The specimen preparation and testing are carried out as per ASTM standards. The values of mechanical properties of hybrid composites plotted against glass fiber weight fraction show significant improvement after the inclusion of glass fiber. Addition of 16.5 wt% glass fiber, in a total fiber weight fraction of 42% enhances the tensile, flexural, and interlaminar shear strength (ILSS) by 37, 31.23, and 17.6% respectively. The behavior of the composite under different tests is analyzed with the help of performance curves. Water absorption plots for different periods of immersion indicated that jute– glass hybrid composites offer better resistance to water absorption. The results of fractographic tests carried out to study the modes of fracture, fiber–matrix adhesion, and jute–glass layer adhesion are also presented.

Static and dynamic behavior of single‐edge notched glass fabric composites

AbstractThis article describes the results of a series of tests conducted to support the development of a semiempirical model, for predicting the mechanical degradation of a satin weave glass fabric composite, with through‐thickness damage in the form of a crack‐like edge‐centered notch. Test specimens were subjected to loading in both static three‐point bending and dynamic mechanical thermal analysis (DMTA) tests. The effect of both notch length and displacement rate, on the static and that of notch length on the dynamic behavior of the materials tested, was evaluated and compared with respective predictions, as derived from the application of the residual property model. A satisfactory agreement between the experimental results and theoretical predictions was observed in all cases. Scanning electron microscopy was applied to observe the failure topographical characteristics of the DMTA specimens that were off‐plane loaded. POLYM. COMPOS. 27:177–183, 2006. © 2006 Society of Plastics Engineers.

Effect of Post-Cure Time on Mechanical Properties of Plain-Woven Glass Fabric Composites

This paper presents the effect of post-cure time on mechanical properties of plain woven glass/vinylester composites. The post-cure of composites was carried out by means of the post-cure duration at the constant temperature 80°C for 4, 8, 16, 24h. The mechanical properties such as Vickers hardness of resin, storage modulus, loss modulus, glass transition temperature, flexural strength and modulus were measured for plain woven GFRP laminates after 80°C post-cure treatment at times ranging from 4h to 24h. It was found that the post-cure treatment improved the dynamic viscoelastic properties and the mechanical properties of plain woven GFRP laminates except for the type of the prolonged post-cure time such as 24h. The shrinkage of the laminates appeared in only the transverse direction after post-cure. Then, the microscopic observation was carried out in order to estimate the degree of internal damage in plain woven GFRP. Delamination occured in the laminates of the type of the low post-cure time as 0h, 4h and the prolonged post-cure time as 24h. Matrix cracking occured in the laminates cured at 80°C from 8h to 16h. It was suggested that the post-cure accelerated the cross-linking reaction in plain woven GFRP laminates. In addition, it was shown that the adhesive strength of the fiber-matrix interface increased by means of post-cure. It was also found that the prolonged post-cure time has weakened the adhesive strength of the fiber-matrix interface.

織物強化複合材料の損傷進展に及ぼす繊維束形状の影響

This paper presents experimental view of damage initiation and growth in plain woven fabric composites, which has several types on woven structure. Plain woven glass fabric composites were fabricated with tensioning the warp during the cure process. Microscopic damage progress was observed by a replica method. Binarization was applied in order to evaluate cracks in the weft and amplitude and curvature radius in plain woven fabric composites. It was found that the amplitude of the warp decreased and the fiber volume fraction in the weft became uniform in order to tension the warp during cure process. In addition, it was clear that the occurrence of cracks in the weft was delayed and the crack was developed slowly on these effects in comparison with the controlled type.

Effect of the shear and coupling elements of the Aij and Dij matrices on the impact behavior of glass, aramid and hybrid fabric composites

The impact behavior of glass, aramid and glass–aramid hybrid fabric epoxy matrix composites was evaluated. Delamination was identified as the main macroscopic failure mode of the composites. A simple relationship based on the macromechanical behavior of laminated composites was established, relating coupling— A 26, D 26—and shear— A 16, D 16—elements of the extensional and bending stiffness matrices to the total energy absorbed at impact. The results obtained show that the A 66/ D 66 ratio is a relevant parameter of concern, correlated with the behavior of the composites under impact. Additionally, the coupling matrix B ij was shown to restrain the macroscopic delamination of the composites.

Pultruded Fabric-Cement Composites

The use of reinforcement in thin cement-based elements is essential to improve the tensile and flexural performance. The reinforcements can be either short fibers or continuous reinforcements, in a fabric form. Practical use of fabric-cement composites requires an industrial, cost-effective production process. The objective of this study was to develop the pultrusion technique as an industrial, cost-effective production method of prefabricated thin-sheet fabric-reinforced cement composites. Woven fabrics made from low-modulus polyethylene and glass meshes were used to produce the pultruded cement composites. The influence of fabric type, cell opening, application of pressure during casting, and cement-based matrix modification were examined. The tensile strength and ductility of the pultruded fabric-cement components were found to be relatively high, exhibiting strain hardening behavior even for fabrics with low modulus of elasticity. The best performance was achieved from glass fabric composites with a high content of fly ash. The mechanical properties were significantly affected by the matrix formulation, rheology of the matrix, and the intensity of the pressure applied after the pultrusion process. The promising combination of fabric reinforcement in cement composite products using the pultrusion process is expected to lead to a new class of high-performance fabric-cement composite materials.

Study on the friction and wear properties of glass fabric composites filled with nano- and micro-particles under different conditions

The glass fabric composites filled with the particulates of polytetrafluoroethylene (PTFE), micro-sized MoS 2, nano-TiO 2, and nano-CaCO 3, respectively, were prepared by dip-coating of the glass fabric in a phenolic resin containing the particulates to be incorporated and the successive curing. The friction and wear behaviors of the resulting glass fabric composites sliding against AISI-1045 steel in a pin-on-disk configuration at various temperatures were evaluated on a Xuanwu-III high temperature friction and wear tester. The morphologies of the worn surfaces of the filled glass fabric composites and the counterpart steel pins were analyzed by means of scanning electron microscopy, and the elemental distribution of F on the worn surface of the counterpart steel was determined by means of energy dispersive X-ray analysis (EDXA). It was found that PTFE and nano-TiO 2 particulates as the fillers contributed to significantly improve the friction-reducing and anti-wear properties of the glass fabric composites, but nano-CaCO 3 and micro-MoS 2 as the fillers were harmful to the friction and wear behavior of the glass fabric composites. The friction and wear properties of the glass fabric composites filled with the particulate fillers were closely dependent on the environmental temperature and the wear rates of the composites at elevated temperature above 200 °C were much larger than that below 150 °C, which was attributed to the degradation and decomposition of the adhesive resin at excessively elevated temperature. The bonding strengths between the interfaces of the glass fabric, the adhesive resin, and the incorporated particulates varied with the types of the particulate fillers, which largely accounted for the differences in the tribological properties of the glass fabric composites filled with different fillers. Moreover, the transferred layers of varied features formed on the counterpart steel pins also partly accounted for the different friction and wear behaviors of the unfilled glass fabric and the composites. In a practical viewpoint, 10% PTFE-filled glass fabric composite could be suitable to tribological applications at moderately elevated temperature.

Determination of the post-ballistic impact mechanical behavior of a ±45° glass–fabric composite

Delaminated areas produced by ballistic impacts on a ±45 ° glass–fabric composite were measured by digital image analysis. The post-impact performance of the composite, as measured by the tensile stiffness and Charpy impact energy of macroscopically undamaged, delaminated and bullet trespassed specimens was determined, and correlated to the effect caused by the presence of the delaminated areas. The results obtained show that two conditions must be satisfied so that delaminated areas seriously affect the post-ballistic behavior of the composite, namely: the presence of shear stresses and delaminated areas above a threshold value.

Mechanical properties of glass fabric/polyester composites: Effect of silicone coatings on the fabrics

AbstractAn experimental investigation was carried out to study the effect of a silicone coating on the mechanical properties of polyester/woven glass fabric composites, fabricated by resin transfer molding. E‐glass woven fabrics were coated with a silicone elastomer by solution dip coating. The effect of variation of silicone amounts on the impact resistance, toughness, and mechanical properties of the composite was determined. Short beam shear tests were performed to assess the effect of coating on the adhesion of the fiber to the matrix. The coated specimens exhibited worse interlaminar shear strength over that of uncoated fabrics. Three‐point bending tests were also performed to investigate the effect of the coating on flexural properties. Whereas flexural strength and Young's modulus decreased with increasing amount of coating, the toughness, represented by the area under the stress–strain curve, presented a maximum. Finally, notched Izod impact tests were carried out and the curve for the energy absorbed during impact versus the amount of coating also appeared to have a maximum, indicating an interesting slot for optimum impact performance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1300–1308, 2004

Novel Glass Polymer Multilayer Composites with High Toughness

With a view to developing low cost glass polymer multilayer composites (GPMLC) with high toughness, four layer laminar glass-epoxy-E glass fabric composites (GEF) were fabricated by a low pressure lamination technique. To promote weaker interfaces a thin sprayed layer of kerosene was introduced between the glass and the reinforcing layer in another group of composites (GEFK) fabricated in a similar manner. In both GEF and GEFK composites, a thin commercial cover slip gas disk (diameter 18 mm, thickness 0.3 mm) was used as the matrix layer. The load displacement plots of the GEF and GEFK composites exhibit a significant degree of non-linearity and stepped load-unload behaviour characteristic of fibre reinforced composites. The specific failure toad (»200 N/mm) and the total work of failure per unit volume (»300 kJ.m−3) of the GEFK composite were found out to be the highest, thus indicating the development of a very high toughness material. These values were much higher than those of the brittle glass matrix, e.g., 20 N/mm and 20 kJ.m−3. The GEF composites showed the second best characteristics.

308 平織りガラス繊維強化複合材料の機械的特性に及ぼすポストキュアの影響

308 平織りガラス繊維強化複合材料の機械的特性に及ぼすポストキュアの影響

Manufacture of Thick Cross-Section Composites Using a Pre-Catalyzed Fabric Technique

The development of a technique is reported for the manufacture of thick unsaturated polyester matrix resin composites using pre-catalyzed glass fabric. Composites over 2 cm thick using glass fabric that was pre-catalyzed (sized) with benzoyl peroxide were compared to composites made using conventional premixed catalyst and resin compounds. The pre-catalyzed fabric is shown to result in reduced internal temperatures during curing. This allows for the construction of thick fiber reinforced composite materials that do not suffer thermal degradation during the curing process. Mechanical testing of prepared thick composites demonstrated that the pre-catalyzed glass fabric composites were significantly stronger than conventionally prepared composites. The center regions of pre-catalyzed composites were about 80% stronger under tension, 25% stronger in compression and 35% stronger under shear than those of conventionally prepared composites of the same thickness. The pre-catalyzed composites were also more uniformly consolidated. Previous work aimed at the manufacture of thick composites has utilized controlled curing by use of expert systems, local resistance heating within the composite or the addition of chemical inhibitors. A method for staged curing has also shown considerable promise. None of these methods, however, has enabled high volume production of high quality thick composites. This paper presents the results of a new method for manufacture of thick composites based on a pre-catalyzed fabric technique.

Study on the Non-Liner Stress-Strain Relation and Progressive Damage of Plain Woven GFRP under Tension/Tension/Torsion Multiaxial Loading.

S-S relationships and progressive damage of a glass fabric composite were studied at multi-axial stress state when normal (σ1 andσ2) and shear (τ12) combined stresses were simultaneously applied to thin-walled tubular specimens parallel to the material axes. The experimental results revealed that the S-S relationships in both normal directions were represented by two straight lines intersecting each other at their knee points while the S-S curve in shear is curvilinear and convex downward. Initial yielding surface could be represented by quadratic whose bottom is square and the height is given by the shear yielding stress. The Hill's yield criterion is not applicable to predict the non-linear S-S relationships after yielding. The material failure envelope at multi-axial stress state was given by a combination between the maximum stress theory and Tsai-Wu failure criterion.

Rubber modification of low temperature cure cyanate ester matrices and the performance in glass fabric composites

AbstractLow temperature cure cyanate ester resin systems were developed and modified with epoxy‐terminated butadiene acrylonitrile rubber (ETBN) and impregnated into woven glass fabric. Mode I and mode II interlaminar fracture toughness values of the cured laminates were evaluated as a function of rubber concentration. Mode I fracture toughness increased to almost twice that of the unmodified system, while mode II fracture toughness remained essentially unchanged. Composite samples were subjected to aging experiments in water and the absorption/desorption behavior was investigated as was the effect on thermal performance. The presence of rubber was found to reduce the rate of matrix deterioration but also caused a substantial increase in water uptake. It was found that although the addition of rubber to the matrices decreased the unconditioned (dry) Tg all specimens showed the same reduction in Tg, after equilibrium water absorption.