Resin-impregnated Fiber Research Articles

Computational co-design of fibrous architecture

Fibrous architecture constitutes an alternative approach to conventional building systems and established construction methods. It shows the potential to converge architectural concerns such as spatial expression and structural elegance, with urgently required resource effectiveness and material efficiency, in a genuinely computational approach. Fundamental characteristics of fibre composite are shared with fibre structures in the natural world, enabling the transfer of design principles and providing a vast repertoire of inspiration. Robotic fabrication based on coreless filament winding, a technique to deposit resin impregnated fibre filaments with only minimal formwork, as well as integrative computational design methods are imperative to the development of complex fibrous building systems. Two projects, the BUGA Fibre Pavilion as an example for long-span structures, and Maison Fibre as an example of multi-storey architecture, showcase the application of those techniques in an architectural context and highlight areas of further research opportunities. The highly interrelated aesthetic, structural and fabrication characteristics of fibre nets are difficult to understand and go beyond a designer’s comprehension and intuition. An AI powered, self-learning agent system aims to extend and thoroughly explore the design space of fibre structures to unlock the full design potential coreless filament winding offers. In order to ensure feedback between all relevant design and performance criteria and enable interdisciplinary convergence, these novel design methods are embedded in a larger co-design framework. It formalizes the interaction of involved interdisciplinary domains and allows for interactive collaboration based on a central data model, serving as a base for design optimisation and exploration. To further advance research on fibre composites in architecture, bio-based materials are considered, continuing the journey of discovery of fibrous architecture to fundamentally rethinking design and construction towards a novel, computational material culture in architecture.

Computational co-design framework for coreless wound fibre–polymer composite structures

AbstractIn coreless filament winding, resin-impregnated fibre filaments are wound around anchor points without an additional mould. The final geometry of the produced part results from the interaction of fibres in space and is initially undetermined. Therefore, the success of large-scale coreless wound fibre composite structures for architectural applications relies on the reciprocal collaboration of simulation, fabrication, quality evaluation, and data integration domains. The correlation of data from those domains enables the optimization of the design towards ideal performance and material efficiency. This paper elaborates on a computational co-design framework to enable new modes of collaboration for coreless wound fibre–polymer composite structures. It introduces the use of a shared object model acting as a central data repository that facilitates interdisciplinary data exchange and the investigation of correlations between domains. The application of the developed computational co-design framework is demonstrated in a case study in which the data are successfully mapped, linked, and analysed across the different fields of expertise. The results showcase the framework’s potential to gain a deeper understanding of large-scale coreless wound filament structures and their fabrication and geometrical implications for design optimization.

Tow Deformation Behaviors in Resin-Impregnated Glass Fibers under Different Flow Rates

With the rapid development of high-performance fibers such as carbon, enhanced glass fibers in structural applications, the use of fiber-reinforced composite (FRC) materials has also increased in many areas. Liquid composite molding (LCM) is a widely used manufacturing process in composite manufacturing; however, the rapid impregnation of resin in the reinforcing fibers during processing poses a significant issue. The optimization of resin impregnation is related to tow deformations in the reinforcing fibers. The present study therefore focuses on this tow deformation. The permeability behaviors in double-scale porous media were observed under different flow rates and viscosity conditions to examine the overall tendencies of structural changes in the reinforcement. The permeability results showed hysteresis with increasing and decreasing flow rate conditions of 50–800 mm3/s, indicating structural changes in the reinforcement. The tow behaviors of the double-scale porous media with respect to the thickness and flow rate were investigated in terms of the representative indices of the minor axis (tow thickness) and major axis. The minor axis and major axis of the tow showed decreasing and increasing trends of 2–5% and 2%, respectively, with minimum and maximum values at different positions along the reinforcement, affected by the different hydrodynamic entry lengths. Finally, the deformed tow behavior was observed microscopically to examine the behavior of the tow at different flow rates.

Design and construction of a continuous impregnation apparatus of woven fibres, using non-meshing double-sinusoidal toothed rollers

Resin-impregnated fibres are extensively used in a variety of industrial applications as is demonstrated in the literature. Resin-fibre impregnation techniques are used in order to create homogeneous macro – materials and to take full advantage of the mechanical properties of the fibrous reinforcement (i.e. carbon, glass, organic or ceramic fibres). However, achieving highly impregnated fibres is proven quite challenging especially in continuous production techniques that are required for large production rates. The main challenge lies in achieving complete impregnation of the tightly arranged fibres mainly referring to the formed yarns containing multiple fibres, sometimes even twisted. This results in partially impregnated materials containing cavities that tend to exhibit inferior mechanical properties compared to the theoretical calculations, which assume fully impregnated materials. These cavities often lead to crack generation, acting as stress concentration sites, resulting in complete failure of the material at macro-level. In this paper a novel technique for continuous production of fully impregnated woven fibres is presented using non – meshing, co – rotating rollers. A laboratory-scale apparatus is designed and described thoroughly in the context of this work. The method resembles pultrusion in the sense that a reinforcement plain fibre mesh (glass) is co–processed with the liquid resin through a pair of co–rotating toothed rollers to produce a continuously reinforced 3D tape. The surface of the rollers is produced from a double-sinusoidal toothed surface (rack) using the Theory of Gearing in three-dimensions, which imposes significant differential sliding of the fibres without differential tension and facilitates fibre wetting. The geometry of the rollers is calculated not to damage the unprocessed fibres, while facilitating local widespreading of the stranded fibres in the three – dimensional space leading to the resin being able to fully penetrate the reinforcing fibre material.

Experimental approach of tow behaviors in resin-impregnated glass fiber for GFRP manufacture

Experimental approach of tow behaviors in resin-impregnated glass fiber for GFRP manufacture

Effect of filler loading on mechanical properties of pultruded kenaf fibre reinforced vinyl ester composites

Pultrusion is one of the polymer composite fabrication processes employing a combination of pulling and extrusion processes. The composite profiles are obtained by pulling resin-impregnated fibres through a series of heated dies. The ability of the pultrusion technique to support a high volume of fibre fraction produces the high stiffness of the composite profile. There are many parameters such as filler loading, mould temperature and pulling speed to be considered and controlled during the pultrusion process. In this paper, an investigation of the effect of the filler loading on the tensile and flexural properties of the pultruded kenaf reinforced vinyl ester composites is presented. As the filler loadings were increased to a significant amount, the mechanical properties started to drop, which was attributed to the increase of viscosity in the matrix and in turn the increase in porosity and decrease in the wettability of the composites. Hence, increasing the amount of filler loading increased the tensile and flexural properties of the pultruded composites in terms of strength and stiffness. The tensile properties of the composites had increased by up to 50% of fibre loading. The maximum flexural strength and modulus were obtained at 30 and 50% of filler loadings respectively. The maximum compressive strength was observed to take place at 40% of filler loading.

The influence of bath temperature on the properties of pultruded glass fiber reinforced rods

Pultrusion is one of the several manufacturing processes for polymer composites. It involves resin-impregnated fibers that passed through a heated die, while the resin cures to produce a solid profile in the desired shape. Many processing variables such as die temperature, pull speed, fiber impregnation, resin viscosity, among others, affect the composite quality and the process efficiency. In fact, a good understanding and careful control of all these variables are needed to avoid defective profiles as well as to achieve better processing conditions. In this paper, the relationship between the resin bath temperature and the mechanical properties of pultruded rods such as tensile strength, elastic modulus, and hardness was established. The effect of resin viscosity on the fibers wet-out, cure position inside the die and the void formation was also investigated. The results showed that the rods made at higher bath temperatures presented higher tensile strength, elongation at break and hardness, but lower modulus of elasticity. This behaviour was correlated with the void content yielded during the profile formation.

The Influence of Composite Thickness with or without Fibers on Fracture Resistance of Direct Restorations in Endodontically Treated Teeth.

This in vitro study evaluated the influence of composite thickness (with or without fiber reinforcement) on fracture resistance of direct restorations in endodontically treated teeth. Fifty-six intact human premolars were chosen and randomly divided into four groups (n=14). After preparation of a mesio-occluso-distal (MOD) cavities and cusp reduction, the teeth were endodontically treated. Subsequently, the samples were restored with composite resin using the following protocols: group 1; composite onlay with cusp coverage of 1.5 mm, group 2; composite onlay with cusp coverage of 2.5 mm, group 3; composite onlay (including resin-impregnated fiber) with cusp coverage of 1.5 mm and group 4; composite onlay (including resin-impregnated fiber) with cusp coverage of 2.5 mm. The fracture resistance of teeth in all test groups was calculated by subjecting them to a progressively increasing compressive axial force in the universal testing machine with the cross-head speed of 1 mm/min to the point of fracture. The data were analyzed using the Kruskal-Wallis test. The mean fracture strengths and obtained standard error were 1263.85±74.03 N, 1330.26±128.01 N, 1344.92±64.40 N and 1312.54±75.63 N for groups 1 to 4, respectively. Statistical analysis revealed no significant difference between groups. Cusp coverage of 1.5 and 2.5 mm in MOD access cavities with or without insertion of resin impregnated fiber had similar fracture rates in the endodontically treated teeth.

Tensile strength distribution of carbon fibers at short gauge lengths

In this study, we determined the strength distribution of high-strength polyacrylonitrile-based carbon fibers of different short gauge lengths (~1 mm) using both the single-fiber-composite four-point bending test and the single-fiber tensile test. We employed the bimodal Weibull model to explain the experimental data. We found that the value of the Weibull shape parameter for short gauge lengths was higher than that for long gauge lengths. This implies that the tensile strength distribution of carbon fibers is governed by two different flaw populations. The tensile strength of resin-impregnated fiber bundles predicted on the basis of the bimodal Weibull distribution was in better agreement with the experimental result than the tensile strength of those predicted on the basis of the unimodal Weibull distribution.

Study of Maleic Anhydride Grafted Polypropylene Effect on Resin Impregnated Bamboo Fiber Polypropylene Composit

Previously, Polyvinyl Alcohol (PVA) and phenolic resin were used for resin impregnated bamboo fiber reinforced PP composites which was manufactures for resin impregnated bamboo fiber with polypropylene (PP). Resin impregnation method can show improvement on tensile strength of fiber. However, to reduce the contact surface area and low inter-facial shear strength (IFSS) between impregnated resin and matrix, using 40% weight fraction of bamboo fiber in PP matrix, PVA impregnated composites with mean flexural and tensile strength 10% higher than untreated composites were produced butphenolic resin impregnated fiber reinforced composition’s mechanical properties were decreased. In this study maleic anhydride grafted polypropylene (MAPP) was used to increase interfacial shear strength between resin impregnated fiber and PP. With 10% MAPP, IFSS between resin impregnated fiber and PP increased more than 100% and reinforced composites. MAPP with untreated, phenolic resin and PVA impregnated cases showed similar mechanical properties. Yet in water absorption test, the PVA treatment with bamboo/PP composites increased water absorption ratio. But with 10% MAPP, matrix PP water absorption ratio decreased like phenolic resin impregnated fiber reinforced composites. 10% MAPP with resin impregnated bamboo fiber reinforced PP composites can improve IFSS, mechanical properties of composite and can decrease water absorption PVA resin impregnated bamboo fiber reinforced composites.

The Friction Force Determination of Large-Sized Composite Rods in Pultrusion

Nowadays, the simple pull-force models of pultrusion process are not suitable for large sized rods because they are not considered a chemical shrinkage and thermal expansion acting in cured material inside the die. But the pulling force of the resin-impregnated fibers as they travels through the heated die is essential factor in the pultrusion process. In order to minimize the number of trial-and-error experiments a new mathematical approach to determine the frictional force is presented. The governing equations of the model are stated in general terms and various simplifications are implemented in order to obtain solutions without extensive numerical efforts. The influence of different pultrusion parameters on the frictional force value is investigated. The results obtained by the model can establish a foundation by which process control parameters are selected to achieve an appropriate pull-force and can be used for optimization pultrusion process.

Impact Analysis of Aluminum-Fibre Laminated Composite

Impact analysis of an advanced laminated composite comprising aerospace 2024-T3 aluminum alloy and resin impregnated E-glass fiber layers with different stacking sequences is presented in the paper. The panel under study is subjected to load-time history equivalent to the low velocity crash using FEM software ANSYS 12. Stress values in the laminate are found to be discontinuous at the interfaces whereas the displacements are continuous across the interfaces. The maximum stress and displacement values in the laminate are comparable with those in monolithic aluminum alloy panel of same thickness.

Effects of Bond Primers on Bending Strength and Bonding of Glass Fibers in Fiber-Embedded Maxillofacial Silicone Prostheses

To evaluate the effect of three commonly used bond primers on the bending strength of glass fibers and their bond strength to maxillofacial silicone elastomer after 360 hours of accelerated daylight aging. Eighty specimens were fabricated by embedding resin-impregnated fiber bundles (1.5-mm diameter, 20-mm long) into maxillofacial silicone elastomer M511 (Cosmesil). Twenty fiber bundles served as control and did not receive surface treatment with primers, whereas the remaining 60 fibers were treated with three primers (n = 20): G611 (Principality Medical), A-304 (Factor II), and A-330-Gold (Factor II). Forty specimens were dry stored at room temperature (23 ± 1°C) for 24 hours, and the remaining specimens were aged using an environmental chamber under accelerated exposure to artificial daylight for 360 hours. The aging cycle included continuous exposure to quartz-filtered visible daylight (irradiance 760 W/m(2) ) under an alternating weathering cycle (wet for 18 minutes, dry for 102 minutes). Pull-out tests were performed to evaluate bond strength between fiber bundles and silicone using a universal testing machine at 1 mm/min crosshead speed. A 3-point bending test was performed to evaluate the bending strength of the fiber bundles. One-way Analysis of Variance (ANOVA), Bonferroni post hoc test, and an independent t-test were carried out to detect statistical significances (p < 0.05). Mean (SD) values of maximum pull-out forces (N) before aging for groups: no primer, G611, A-304, A-330-G were: 13.63 (7.45), 20.44 (2.99), 22.06 (6.69), and 57.91 (10.15), respectively. All primers increased bond strength in comparison to control specimens (p < 0.05). Primer A-330-G showed the greatest increase among all primers (p < 0.05); however, bonding degraded after aging (p < 0.05), and pull-out forces were 13.58 (2.61), 6.17 (2.89), 6.95 (2.61), and 11.72 (3.03). Maximum bending strengths of fiber bundles at baseline increased after treatment with primers and light aging in comparison with control specimens (p < 0.05), and were in the range of 917.72 to 1095.25 and 1124.06 to 1596.68 MPa at both baseline and after 360 hours aging (p < 0.05). The use of A-330-G primer in conjunction with silicone Cosmesil M511 produced the greatest bond strength for silicone-glass fiber surfaces at baseline; however, bond strength was significantly degraded after accelerated daylight aging. Treatment with primer and accelerated daylight aging increased bending strength of glass fibers.

Effects of Accelerated Artificial Daylight Aging on Bending Strength and Bonding of Glass Fibers in Fiber‐Embedded Maxillofacial Silicone Prostheses

The purpose of this study was to test the effect of different periods of accelerated artificial daylight aging on bond strength of glass fiber bundles embedded into maxillofacial silicone elastomer and on bending strength of the glass fiber bundles. Forty specimens were fabricated by embedding resin-impregnated fiber bundles (1.5-mm diameter, 20-mm long) into maxillofacial silicone elastomer. Specimens were randomly allocated into four groups, and each group was subjected to different periods of accelerated daylight aging as follows (in hours); 0, 200, 400, and 600. The aging cycle included continuous exposure to quartz-filtered visible daylight (irradiance 760 W/m(2)) under an alternating weathering cycle (wet for 18 minutes, dry for 102 minutes). Pull-out tests were performed to evaluate bond strength between fiber bundles and silicone using a universal testing machine at 1 mm/min crosshead speed. Also a three-point bending test was performed to evaluate bending strength of the fiber bundles. One-way ANOVA and Bonferroni post hoc tests were carried out to detect statistical significance (p < 0.05). Mean (SD) values of maximum pull-out forces (in N) for groups 1 to 4 were: 13.63 (7.45), 19.67 (1.37), 13.58 (2.61), and 10.37 (2.52). Group 2 exhibited the highest pull-out force that was statistically significant when compared to the other groups. Maximum bending strengths of fiber bundles were in the range of 917.72 MPa to 1124.06 MPa. Bending strength significantly increased after 200 and 400 hours of aging only. After 200 hours of exposure to artificial daylight and moisture conditions, bond strength between glass fibers and heat-cured silicones is optimal, and the bending strength of the glass fiber bundles is enhanced.

An optimization procedure for the pultrusion process based on a finite element formulation

AbstractComposite materials are manufactured by different processes. In all, the process variables have to be analyzed in order to obtain a part with uniform mechanical properties. In the pultrusion process, two variables are the most important: the pulling speed of resin‐impregnated fibers and the temperature profile (boundary condition) imposed on the mold wall. Mathematical modeling of this process results in partial differential equations that are solved here by a detailed procedure based on the Galerkin weighted residual finite element method. The combination of the Picard and Newton‐Raphson methods with an analytical Jacobian calculation proves to be robust, and a mesh adaptation procedure is presented in order to avoid integration errors during the process optimization. The two earlier‐mentioned variables are optimized by the Simulated Annealing method with some constraints, such as a minimum degree of cure at the end of the process, and the resin degradation (the part temperature cannot be higher than the resin degradation temperature at any time during the whole process). Herein, the proposed objective function is an economic criterion instead of the pulling speed of resin‐impregnated fibers, used in the majority of papers.

Compression in the processing of polymer composites 2. Modelling of the viscoelastic compression of resin-impregnated fibre networks

This paper presents a study of the viscoelastic compression of resin-impregnated fibre cloths. The experiments included a type of plain-weave cloth and two types of resin, an epoxy behaving approximately as a Newtonian fluid and a polyester following power-law, non-Newtonian behaviour. The experimental studies of viscoelastic compression included a review of compression tests at two different compression speeds, and also compression hysteresis tests and pressure relaxation tests. The mathematical analysis covered the development of a viscoelastic model in which the total applied pressure during compression was split between the pressure to compress the assembly of fibre cloths and the pressure required for the resin flow through the deformable, porous medium. It considers elastic and viscoelastic effects from the fibre medium, and viscous and elastic effects from flowing resin. Regarding the type of resin, it includes modelling of both a Newtonian and a non-Newtonian fluid. The model was fitted to the experimental data for wet compression for both types of resin and yielded best-fit values for parameters from the Carman–Kozeny equation and the non-Newtonian type of Darcy’s law, for the plain-weave fabric used.

Non-ferrous reinforcement

Traditionally, concrete structures have been reinforced with steel bars or prestressed with steel wires or strands. Generally, embedded steel is very durable, the concrete providing a suitable alkaline environment. However, for structures in highly aggressive environments, the protection afforded by the concrete is often insufficient to ensure the necessary service life for the structure. In addition to attempts to improve the quality of the concrete itself, there are a number of approaches for protecting the steel directly, such as by means of epoxy coating or the use of cathodic protection. A further alternative is to replace the steel completely by a material that will, hopefully, be more durable. One such option, which has great potential, is the use of fibre-reinforced plastics (FRPs), which consist of continuous fibres, generally of glass, carbon or aramid, set in a suitable resin to form a rod or grid. These materials are well accepted by the aerospace and automotive industries and are starting to find applications in the construction industry. The mechanical properties of FRPs are chiefly determined by the amount and type of fibre, while the durability will be a function of both the resin and the fibre. The strength of FRP reinforcement will tend to be between that of high-yield reinforcing steel and prestressing stand (say 1000 N/mm2 for glass fibres and 1500 N/mm2 for carbon fibres) but the stiffness will generally be significantly lower (say 45 kN/mm2 for glass fibres and 150 kN/mm2 for carbon fibres). All FRP materials have a straight line response to failure with no plasticity. The most common method for manufacturing FRP rods is pultrusion, in which the fibres are drawn off storage containers in a controlled pattern, are impregnated with resin and then drawn through a heated die which sets and cures the resin. One limitation at present is that thermoset resins are generally used and, hence, once fully cured, rods cannot be bent into the range of shapes currently used with steel. Thus ‘specials’ are required. Spiral reinforcement, either circular or rectangular in form, is produced by some Japanese manufacturers along with two- or three-dimensional grid. Other manufacturing techniques are being developed in which resin-impregnated fibres are wound on to suitable mandrels to producing closed shapes, such as shear links. As an alternative, thermoplastic resins are being developed, which would allow the fully cured material to be bent.

Resin-impregnated fibre composite materials and a process for their manufacture: Andersson, B. (KemaNord AB, Stockholm, Sweden) US Pat 4 451 585 (29 May 1984)

Resin-impregnated fibre composite materials and a process for their manufacture: Andersson, B. (KemaNord AB, Stockholm, Sweden) US Pat 4 451 585 (29 May 1984)

Oxygen Flux: Field Measurement Using a Polarographic Recorder

SUMMARY (1) Oxygen flux in waterlogged forest soils can be measured using the platinum microcathode technique. By automatically scanning a predetermined voltage range applied to each set of up to twenty-four microcathodes in turn, the instrument described produces a set of polarograms from which a flux-derived current can be unambiguously determined. (2) Examples of different types of polarogram are given and the degree of desaturation is indicated by the shape of the polarogram. (3) The robust microcathodes are made of a hard platinum-iridium alloy cased in resin-impregnated glass fibre, the whole instrument being rugged, portable and capable of running unattended in adverse environments. (4) Applied potential and scanning rate can be preselected, usually 0 to - 500 mV at 33 mV min-. (5) Difficulty in extrapolating transient to steady state diffusion and the uncertainty associated with the exact cathodic processes involved are discussed.