Unidirectional Continuous Fiber Research Articles

Mechanical Behavior of Continuous Fiber-Reinforced Elastomeric Materials at Finite Strain

A constitutive model is developed to characterize mechanical behavior of unidirectional continuous fiber-reinforced elastomeric materials at finite strains. Assuming transversely isotropic behavior, strain energy of elastomeric composite is expressed as polyconvex functions of principal invariants defined by tensors describing deformation field and fiber directions. Parameters of polyconvex functions are evaluated based on homogenization of incompressible elastomeric matrix reinforced with unidirectional inextensible continuous fibers. Heterogeneous microstructure is identified by a representative volume element subjected to equivalent macroscopic deformations. Micromechanical results show that the strain energy of unidirectional fiber-reinforced elastomers can accurately be described by additive decomposition into isotropic and anisotropic models.

Load-bearing capacity of fiber reinforced fixed composite bridges

Objective. The aim of this study was to evaluate the reinforcing effect of differently oriented fibers on the load-bearing capacity of three-unit fixed dental prostheses (FDPs). Materials and methods. Forty-eight composite FDPs were fabricated. Specimens were divided into eight groups (n = 6/group; codes 1–8). Groups 1 and 5 were plain restorative composites (Grandio and Z100) without fiber reinforcement, groups 2 and 6 were reinforced with a continuous unidirectional fiber substructure, groups 3 and 7 were reinforced with a continuous bidirectional fiber and groups 4 and 8 were reinforced with a continuous bidirectional fiber substructure and continuous unidirectional fiber. FDPs were polymerized incrementally with a handheld light curing unit for 40 s and statically loaded until final fracture. Results. Kruskal–Wallis analysis revealed that all groups had significantly different load-bearing capacities. Group 4 showed the highest mean load-bearing capacity and Group 7 the lowest. Conclusion. The results of this study suggest that continuous unidirectional fiber increased the mechanical properties of composite FDPs and bidirectional reinforcement slowed crack propagation on abutments.

Effect of monomer composition of polymer matrix on flexural properties of glass fibre-reinforced orthodontic archwire

To compare force levels obtained from glass fibre-reinforced composite (FRC) archwires. Specifically, FRC wires were compared with polymer matrices having different dimethacrylate monomer compositions. FRC material (E-glass provided by Stick Tech Ltd, Turku, Finland) with continuous unidirectional glass fibres and four different types of dimethacrylate monomer compositions for the resin matrix were tested. Cross-sectionally round FRC archwires fitting into the 0.3 mm slot of a bracket were divided into 16 groups with six specimens in each group. Glass fibres were impregnated by the manufacturer, and they were initially light-cured by hand light-curing unit or additionally post-cured in light-curing oven. The FRC archwire specimens were tested at 37°C according to a three-point bending test in dry and wet conditions using a span length of 10 mm and a crosshead speed of 1.0 mm/minute. The wires were loaded until final failure. The data were statistically analysed using analysis of variance (ANOVA). The dry FRC archwire specimens revealed higher load values than water stored ones, regardless of the polymer matrix. A majority of the FRC archwires showed higher load values after being post-cured. ANOVA revealed that the polymer matrix, curing method, and water storage had a significant effect (P < 0.05) on the flexural behaviour of the FRC archwire. Polymer matrix composition, curing method, and water storage affected the flexural properties and thus, force level and working range which could be obtained from the FRC archwire.

Fiber-reinforced composite fixed dental prostheses: a retrospective clinical examination.

To obtain survival data on 32 fiber-reinforced fixed dental prostheses which were inserted in our department and to rate the quality of these restorations on the basis of esthetic, biological, and functional parameters. Thirty-two patients with fiber-reinforced fixed dental prostheses were included in the study. The fiber frameworks were made of a polymer-monomer-preimpregnated continuous unidirectional glass fiber material. The survival times, failure events, and clinical parameters were recorded. Restorations in function without previous failure were classified as "Overall Survival". The classification "Functional Survival" was assigned in the event of minor failure and subsequent repair. Loss of the restoration was regarded as "Failure". The quality rating was performed using modified USHPS/Ryge criteria. The follow-up interval ranged from 2 to 64 months with a median follow-up time of 18.2 months. Twenty-four restorations were classified as "Overall Survival", seven were classified as "Functional Survival", and one was classified as "Failure". The overall survival at the median follow-up time was 74.4%. For the majority, the quality rating (USHPS/Ryge criteria) yielded clinically excellent results in all categories. No restoration was rated as insufficient or poor. Fiber-reinforced composite fixed dental prostheses provide sufficient stability and very good esthetic, biological, and functional performance in the case of specific clinical indications.

Improved nonlinear stress-strain relation for carbon-epoxy composites and identification of material parameters

This study focuses on the comparison of selected nonlinear stress—strain relations for unidirectional continuous fiber carbon—epoxy composites and the identification of their parameters under tensile loading. Simple tensile tests of thin strips with various fiber orientations are performed. One linear relation, two types of nonlinear stress—strain relations taken from literature, and one improved relation are analyzed and used within the identification process. All the relationships are deduced from polynomial expansion of complementary energy density. The process, using a combination of the mathematical optimization method and finite element analysis, is described with the necessary details. Failure analysis for the determination of the first failure using Puck’s action plane concept is also performed. The tensile and shear strengths are investigated. The comparison of the results obtained from the identified material parameters with the results obtained using the material parameters given by manufacturer is included.

Rheological characterization of continuous fiber—reinforced viscous fluid

The present paper describes a micromechanical technique to determine rheological properties of viscous fluid reinforced with unidirectional continuous fibers. Fluid viscosity is described by a shear thinning model and high viscosity is considered for continuous fibers having considerable rigidity compared to net fluid. The microstructure is identified by a representative volume element that is subjected to equivalent macroscopic deformation fields. The energy balance and periodicity conditions are considered to relate deformation and stress in macro and micro-levels. It is shown that response of viscous fluid reinforced with rigid fibers depends on deformation history as well as rate-of-deformation in the transverse intraply shear and transverse squeeze flows. An orthotropic viscous constitutive equation is derived to describe response of such materials. The material viscosities are evaluated for viscous fluid reinforced with different fiber volume fractions during deformation applied in different rates of deformation. The results are used to derive the functions predicting effective anisotropic viscosities of reinforced fluid.

Water absorption of two different denture base resins reinforced with dental fiber systems

AbstractThe absorption of water by denture base materials is important because it is directly related with dimensional stability of dental material. In this study, water absorption of denture base materials reinforced with different type of dental fiber systems was compared. The samples were prepared from heat‐polymerized and microwave polymerized denture base resins and reinforced with different dental fiber systems. Five different reinforcement materials were used in this study, namely, (1) no fiber (control group), (2) plasma‐treated crosslinked polyethylene fibers, (3) plasma‐treated woven polyethylene fibers (4) porous polymer preimpregnated continuous unidirectional glass fibers, and (5) woven glass fibers. The water absorption calculations were done for the periods of 7, 14, 21, and 30 days of water immersion and in total 100 specimens were tested. The statistical analysis via analysis of variance and Duncan multiple comparison tests have shown that the fiber reinforcement significantly influence the water absorption. Moreover, the results have shown that water absorption of denture base polymers is higher when the specimens are reinforced with the fiber systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Systematically varied interfaces of continuously reinforced glass fibre/polypropylene composites: Comparative evaluation of relevant interfacial aspects

Interface related mechanical properties of unidirectional continuous glass fibre (GF)/polypropylene (PP) com- posites made of commingled yarns have been systematically studied according to a three level, three-factor factorial design. The three systematically varied factors comprised different silane coupling agent and film former contents in GF sizings as well as a varying GF diameter. Besides the statistical evaluation of those main effects on the transverse tensile and com- pression shear strengths of the composites, interfacial shear strength measurements on model composites have been per- formed. The latter ones as well as the results of the dynamic mechanical thermal analysis support the statistical significance of sizing components, the sizing content on the GF, and GF diameter for the mechanical properties of the composites. This highlights the interplay of proper sizing formulation and reproducible GF-spinning conditions, as both affect the interfacial bonding of continuously reinforced GF/PP composites.

Longitudinal Modulus of Semi-auxetic Unidirectional Fiber Composites

In micromechanical modeling of composites, it is well known that the Voigt formula or the rule-of-mixture method gives the most general upper bound estimate of the effective Young’s modulus. In this article it is shown that the effective longitudinal Young’s modulus of a continuous unidirectional fiber composite significantly exceeds the rule-of-mixture when both constituents possess equal or almost equal Young’s moduli and opposing Poisson’s ratio signs.

THE STRESS ANALYSIS AND THE CRACK BEHAVIOR ACCORDING TO THE CHARACTERISTIC OF THE INTERFACIAL REGION IN FIBER REINFORCED MMC

High performance composite reinforced with unidirectional continuous fibers are used in applications requiring high stiffness, high strength and light weight. Because of the high stiffness of the reinforced continuous fiber, the longitudinal performance of such unidirectional composites is greatly enhanced, but their transverse performance is so weak. The nature of the fiber/matrix interface is one of the important factors which determine the unique properties of the fiber reinforced metal matrix composites (MMCs). So, the current study is focused on the fracture behavior of the interface. Both stress state of the interface and crack parameters of the perpendicular crack to the interface for unidirectional fiber reinforced metal matrix composites under the transverse loading are investigated by using elastic-plastic finite element analysis. Different fiber volume fractions (5~60%) and arrangement (square and hexagon) of fibers were studied numerically. The fiber/matrix interface was treated as multi thin layer with different material properties. The fiber is assumed as linear elastic SiC and the matrix is assumed as elastic-plastic Ti -15-3 Titanium alloy. The results show that the stress distributions of the multi thin layer model have much less changes compared with a single interface case. And the properties of the interfacial zone affect the stress distribution, crack behavior and mechanical behavior of the fiber reinforced metal matrix composite.

Preparation and Morphology of C/C-SiC Composites by Si Melt Infiltration

Two different types of carbon fibre bundles were used for filament winding to obtain C/C preforms. C/C-SiC composites were produced from the C/C preforms by a silicon melt infiltration technique. The effect of the type of carbon fibre bundle on the mechanical and thermal properties of the resultant C/C-SiC composites was compared. The spun fiber preform yields C/C-SiC composites of better mechanical properties than the unidirectional continuous fiber preform. The strength of the composites from the SFP was 1.8 times higher than that from the CFP. The flexural strength and the O-ring strength of the composites from the SFP with a density of 2.35 g/cm3 were about 160 MPa and 170 MPa, respectively.

Static and fatigue compression test for particulate filler composite resin with fiber-reinforced composite substructure

Objectives The aim of this study was to determine static load-bearing capacity and compressive fatigue limits (CFL) of laboratory particulate filler composite resin (PFC) with three different types of fiber-reinforced composite (FRC) substructures. Methods A total of 420 test specimens were prepared having 1.0 mm of FRC layer as substructure (short random, continuous unidirectional and bidirectional fiber orientations), and a 2.0-mm thick surface layer of PFC. Control specimens were prepared from plain FRC or PFC. The specimens ( n = 15) were either dry stored or water stored (37 °C for 2 weeks) before they were loaded with a steel ball (Ø 3.0 mm) under static load until fracture and cyclic load with maximum controlled regimen following a staircase approach with maximum 10 3 cycles. The decrease in CFL compared to static load was calculated and data were analyzed using ANOVA and Weibull statistics. Results The highest static loads were registered for plain FRC specimens [short random 1842 N(205), continuous bidirectional 2258 N(233) and unidirectional fiber orientation 538 N(254)]. The specimens with FRC substructure and PFC coverage gave load values of 1517 N(249), 1670 N(241) and 677 N(240), respectively. The specimens made of PFC only, failed with 1047 N(230) load. The CFL for 10 3 cycles ranged between 19 and 39% of the static load values. ANOVA revealed that all factors significantly affected the load bearing capacity ( p < 0.001). Significance The results suggested that the material combination of continuous bidirectional or random FRC and PFC, gave higher CFL and static load-bearing capacity than that obtained with plain particulate filler composite resin

Finite element analysis of thermoplastic composite plates in forming temperature

An implicit mixed finite element formulation is developed based on the plate theory to analyze thermoforming process of thermoplastic plates reinforced with unidirectional continuous fibers. The plate thickness variations and the rotation of transverse planes are considered using Reissner–Mindlin approximation in order to model the predominated deformation mechanisms of the transverse fiber flow and intra-ply shear in these highly kinematical constrained materials. The kinematical constrains due to material incompressibility and fiber inextensibility are considered in the plate theory formulations and taken into account in the finite element method by introducing penalty numbers. A new analytical approach is developed to analyze the forming procedure of a composite plate on the single curvature geometry to compare the numerical results with analytical approach. The forming of thermoplastic plates to the hemispherical configuration is also studied by means of finite element technique. The geometry of panel in blank holder region is estimated considering both the effect of blank holder normal pressure and the viscous layers in die contact surfaces. The finite element results show that the geometry and defects due to wrinkling during the shaping procedure may be conventionally predicted using the derived formulations.

Effects of void geometry on elastic properties of unidirectional fiber reinforced composites

Voids are one of the most common types of manufacturing process induced defects in composite materials that have detrimental effect on the material properties. The void content can be reduced by carefully chosen process parameters, such as pressure and temperature, but often at the price of higher cost. A quantitative relationship between void characteristics and material properties would allow the trade-off between the cost and the desired product performance. The characteristics of interest include volume fraction, size, shape, and spatial distribution. In this paper, methods for determining effective elastic constants of unidirectional continuous fiber reinforced composites containing voids of various characteristics are presented. Finite element analysis (FEA) is performed on a representative volume cell based on observed void microstructure to determine the effective elastic constants. Analytical method based on Mori–Tanaka theory is also utilized for comparison. The predictions by FEA and the analytical method are compared with each other as well as with available experimental data. Overall good agreement is found. A parametric study reveals that the void content has severe impact on the out-of-plane modulus, while the in-plane properties are less significantly affected. For a given void content, the shape of the voids has different effect on different moduli. Flat voids are benign for in-plane moduli but undesirable for out-of-plane stiffness. Long voids reduce significantly the out-of-plane shear modulus, but have little effect on the in-plane properties.

Vibration welding of a unidirectional continuous glass fiber reinforced polypropylene GMT

This paper presents experimental results of vibration welding of a continuous fiber GMT composite of E-glass glass fiber reinforced polypropylene. Vibration welding parameters investigated were vibration time, clamping pressure and vibration amplitude. The effects of these parameters on penetration and lap shear strength of the composite were determined. It was shown that clamping pressure and vibration time should be properly selected to optimize the lap shear strength. Temperature measurements made during vibration welding showed the importance of these two parameters on the interface temperature required for proper vibration welding.

Release of chlorhexidine digluconate and flexural properties of glass fibre reinforced provisional fixed partial denture polymer

The objective of this study was to determine the flexural properties and the release of chlorhexidine digluconate (CHX) of CHX laced unidirectional E-glass fibre reinforced provisional fixed partial denture polymer. Bar shaped test specimens (3.3 x 10.0 x 65.0 mm) were fabricated from provisional fixed partial denture polymer (mixture of poly[ethylmethacrylate] powder and n-poly[butyl methacrylate] monomer liquid) with E-glass fibre reinforcements. Poly(methyl methacrylate) preimpregnated continuous unidirectional glass fibre reinforcement was laced with CHX. The glass fibre reinforcements were incorporated into the polymer and the polymerised to the form of test specimens. In addition test specimens without CHX in glass fibre reinforcement were made for comparison. Control specimens did not contain glass fibres in the test specimens. Flexural strength and modulus of test specimens (n = 6) was tested with three-point bending test after storing the specimens dry or in water (two weeks). Released CHX was determined with high performance liquid chromatography during 180 days water immersion. In dry conditions, the flexural strength and the modulus of the polymer was 43 MPa and 1.7 GPa, and with glass fibre reinforcement 96 MPa and 3.5 GPa. With the reinforcement laced with CHX, the strength was 92 MPa and the modulus was 3.2 GPa. The water storage of test specimens did not weaken the reinforced polymer. The majority of the CHX released from the glass fibre reinforced polymer during the first days of storage in water. Flexural properties of provisional fixed partial denture polymer were increased using glass fibre reinforcement. The fibre reinforcement that was laced with CHX resulted in similar reinforcing effect.

Survival rates of resin-bonded, glass fiber–reinforced composite fixed partial dentures with a mean follow-up of 42 months: A pilot study

Statement of problem Although short-term clinical data exist for resin-bonded, glass fiber-reinforced composite fixed partial dentures (FPDs), long-term data are needed. Purpose The survival rates of 29 resin-bonded, glass fiber-reinforced composite fixed partial dentures were evaluated in this clinical study for periods of up to 42 months. Material and methods FPDs were fabricated to replace 1 to 3 missing maxillary or mandibular teeth of 29 patients not able to be treated with conventional FPDs. Originally, there were 37 patients (the drop-out rate was 22%). The FPDs were retained with wings, inlays, complete coverage crowns, or combinations of these that were bonded to tooth structure. The FPD frameworks were made of continuous unidirectional E-glass fibers with a multiphase polymer matrix and light-polymerized particulate composite veneer. The patients were recalled for examinations, where a general dental examination was performed, 1 to 3 times per year for up to 63 months (minimum 24 months, mean 42 months). Partial or complete total debonding of the FPD or the framework fracture was considered a treatment failure. The data were analyzed with the Kaplan-Meier survival test (α = .05). Results Two resin frameworks fractured, and 3 frameworks were debonded. Kaplan-Meier survival probability at 63 months was 75%. Three of the failed FPDs were rebonded or repaired in situ, producing a functional survival rate of 93% after rebonding or repairing (mean survival time was 55 months). Conclusion The results of this clinical study of 29 prostheses suggest that glass fiber–reinforced FPDs may be a possible alternative to cast metal resin-bonded FPDs. These restorations were successfully used as multiple-unit prostheses that employed a variety of abutment tooth preparation designs.

Piezoresistivity in unidirectional continuous carbon fiber polymer-matrix composites: single-lamina composite versus two-lamina composite

Piezoresistivity in unidirectional carbon fiber epoxy-matrix composites was studied by measurement of the electrical resistance of single-lamina and two-lamina composites in the longitudinal (fiber) direction during elastic tensile loading and unloading in the same direction. The piezoresistive effect was reversible. The resistivity increased slightly with longitudinal tensile strain for the single-lamina composite, but decreased with strain for the two-lamina composite. The gage factor was around +2 and -6 for single-lamina and two-lamina composites, respectively. The very weak piezoresistivity in the single-lamina composite was probably due to decrease in the extent of fiber-fiber contact upon tension. The relatively strong piezoresistivity in the two-lamina composite was probably due to increase in the degree of fiber alignment upon tension.

Improvement of Mechanical Properties of Oligomer-modified Acrylic Bone Cement with Glass-fibers

Some mechanical properties of oligomer-modified acrylic bone cement with glass-fibers were studied. Under wet environments, oligomer-filler forms a porous structure in the acrylic bone cement. Test specimens were manufactured using commercial bone cement (Palacos® R) with different quantities of an experimental oligomer-filler (0–20 wt%), and included continuous unidirectional E-glass fibers (l=65 mm) or chopped E-glass fibers (l=2 mm). The specimens were either tested dry, or after being immersed under wet environments for one week. The three-point bending test was used to measure the flexural strength and modulus of the acrylic bone cement composites (analysis with ANOVA). A scanning electron microscope (SEM) was used to examine the surface structure of the acrylic bone cement composites. Using continuous glass-fiber reinforcement, the dry flexural strength was 145 MPa and modulus was 4.6 GPa for the plain bone cement. For the test specimens with 20 wt% of oligomer-filler and continuous unidirectional glass-fibers, the dry flexural strength was 118 MPa and modulus was 4.2 GPa, whereas the wet flexural strength was 66 MPa and modulus was 3.0 GPa. The results suggest that the reduced flexural properties caused by the porosity of oligomer-modified bone cement can be compensated with glass-fiber reinforcement.

Anisotropic Strength Approach for Wear Analysis of Unidirectional Continuous FRP Composites

Based on the anisotropic strength failure criteria, a model is introduced to predict the wear behavior of unidirectional continuous fiber reinforced polymer composites (FRP) for arbitrary fiber orientations. This approach, which includes the influence of the friction on the failure strength, is initially validated by comparison to experimental data for T300/Epoxy. The benefits of the model and trends for variation of wear with fiber orientations are subsequently ascertained and discussed.