Short Fiber Preforms Research Articles

Sustainable Jute Fiber Sandwich Composites with Hybridization of Short Fiber and Woven Fabric Structures in Core and Skin Layers

AbstractSustainable hybrid composites, made of two different natural plant fiber types, are increasingly being attracted by composite researchers, for their cost effectiveness and ability to control mechanical performances through varying weight ratios of different fibers. In contrast, their lower mechanical properties are reported in the literature, because of strength variations of different fiber types and an improper fiber‐matrix stress distribution. Therefore, it is aimed to develop sustainable hybrid composites from two dry fiber preforms—woven fabric and short fiber preform—originated from same fiber type (jute). A highly packed short fiber preform is used as the core layer, while woven fabrics (plain/twill–rib/twill–diamond) are used in the skin layers for producing sandwiched hybrid jute composites. Mechanical tests and scanning electron microscopy images show that hybridized plain fabric/short fiber preform composites have better mechanical properties (≈58 MPa tensile strength/≈117 MPa flexural strength/≈112.12 kJm−2 impact strength with an ≈487.4% improvement) compared to other fabric structures hybrid/nonhybrid composites. This enhancement is related to the interlocking of short fibers with long plain fabric leading to a strong fiber‐matrix interfacial bonding. Thus, this developed hybrid composites, can be applied in many semi‐structural applications, wherein composites’ low cost and mechanical performances are primary concerns.

Interpenetrating Hybrid Reinforcement in Al2O3 Short Fiber Preforms Infiltrated by Al-Si Alloys

In this work, the effect of the Si content and its morphological features on the mechanical properties of different short fiber-reinforced Al-Si matrices is studied. Al-Si alloys with Si contents of 7 wt pct and more contain a percolating Si network in the as-cast condition. The addition of alumina fibers into these Al-Si matrices increases the mechanical properties by forming an interconnected Al2O3-Si network. Both elastic modulus and maximum strength (from tensile and compression tests) increase with increasing Si content, which reinforces the interpenetration. However, Si diffuses toward the fibers’ surface during solution treatment forming coarse Si particles, reducing considerably the connectivity of the Al2O3-Si-hybrid network and thus the mechanical properties of the composites. The mechanical properties of the Al2O3-Si network itself are studied by means of compression tests on extracted hybrid reinforcement samples and are related to the global behavior of the composites. The strength vs true strain curves depict a strain-controlled softening of the composite material, which proceeds the faster, the higher the interconnectivity of the hybrid reinforcement, due to the propagation of damage of the Al2O3-Si network.

Influence of preform preparation condition on infiltration of molten aluminum

Abstract The effects of the preform preparation conditions such as the kind of binder, preform temperature, molten aluminum alloy temperature, the volume fraction (Vf) of reinforcement in preform on the permeability of the A366.0 molten aluminum alloy to FeCrSi metal fiber preform and alumina short fiber preform were investigated. The permeability at 973–1073 K and 0.4 MPa in applied pressure of molten alloy was obtained by using the infiltration speed and Darcy's formula. The permeability of FeCrSi fiber preform and alumina fiber preform increased on increasing the treatment temperature because of the improvement of viscosity of molten alloy at high temperature. On increasing the volume fraction of fiber, the permeability decreased because of the degradation of size of gap in preform. The permeability of FeCrSi fiber preform was greater than that of alumina fiber preform.

Microstructure and strength of a squeeze cast aluminium piston alloy composite reinforced with alumina short fibre using Al2O3 binder

Alumina short fibre preforms were fabricated using an Al2O3 binder and infiltrated with aluminium piston alloy melt by squeeze casting. Al2O3 binder is thermodynamically more stable than the conventional SiO2 binder and reduces the fibre/matrix interfacial reaction. The effects of fibre volume fraction, temperature and heat treatment on the yield strength and tensile strength of the composite were investigated. The Al2O3 binder provided a satisfactory interfacial bond between the fibre and the matrix without any interfacial reaction or fibre damage. Aging behaviour was not changed by reinforcement. At every temperature, the composites showed the highest strength with a fibre volume fraction of 18%. The strength of the composite was improved by T6 heat treatment. Examination of the fracture surfaces and calculation of the tensile strength using the rule of mixtures indicated that the 18% fibre reinforced composite had a strong interfacial bond even at high temperatures.

Microstructures and mechanical properties of engineered short fibre reinforced aluminium matrix composites

Aluminium matrix composites have been fabricated by squeeze casting into short fibre preforms modified on the basis of a phase contiguity model to improve mechanical performance. Fibre junctions were created in a planar random alumina fibre array by (a) sintering, (b) phosphoric acid treatment, (c) phosphoric acid/aluminium hydroxide (P/Al) treatment and (d) infiltration with alumina powder and sintering. The microstructures and mechanical properties of these composites were examined systematically. The results indicate that using phosphoric acid solution itself to create inter-fibre bonds in the preform gave rise to very low composite strength and ductility compared with that resulting from the as-received preform. This is mainly due to the severe damage to the fibres caused by chemical reaction. By employing the P/Al binder to create the cross-links, the composites reinforced with laboratory-made preforms yielded higher tensile strength relative to the uniform fibre reinforced composites without any sacrifice to the ductility and elastic modulus.

Microstructure and Mechanical Properties of Reaction Squeeze Cast Hybrid Al Matrix Composites

Hybrid Al matrix composites reinforced with Kaowool ceramic fiber (Al2O3 · SiO2) and reaction formed intermetallic compound particles, starting compositions of (10%Al2O3 · SiO2 + 5%Ni)/Al and (10%Al2O3 · SiO2 + 5%TiO2)/Al were fabricated employing squeeze casting technique. Microstructures of the Al composites were examined, and the reactivity of Ni and TiO2 powders added to Kaowool short fiber preform with infiltrating molten Al, resulting products of Al3Ni and Al3Ti, during squeeze casting was analyzed. Hardness, strength (at 25 and 300°C) and wear resistance of the composites were characterized. To investigate the fracture behavior of the composites, in-situ fracture test was performed within SEM. The hybrid Al composites revealed the microstructure of uniformly distributed reinforcements (ceramic short fiber and reaction formed intermetallic compounds). Ni powder added hybrid Al composite achieved the highest hardness, strength and wear resistance among the composites. It was found that the strength drop at elevated temperature (300°C) is effectively reduced by hybridization with ceramic fiber and intermetallic compounds reinforced in Al. In-situ fracture observation demonstrated the fracture behavior of Ni powder added hybrid Al composite as microcrack initiated mainly by short fiber/ matrix interfacial debonding and the crack propagated through the cluster of intermetallic compound particles as loading is raised.

Thermal expansion behavior of aluminum alloys reinforced with alumina planar random short fibers

The thermal expansion behavior of two aluminum alloys (Al-4%Cu and Al-12%Si) reinforced with alumina planar random short fibers has been studied, both experimentally and theoretically. The metal matrix composites (MMCs) were manufactured by pressure infiltration of molten metal into short fiber preforms with a planar random distribution of fibers. Dilatometric testing was used to investigate the influence of fiber volume fraction and architecture, and the effects of thermal cycling between 25 °C to ∼560 °C. Thermal expansion measurements showed that, by increasing the fiber content in the composites, both the thermal strains and the effective coefficient of thermal expansion (CTE) were reduced in the whole temperature range. Furthermore, the thermal strains of MMCs increased almost linearly up to a critical temperature, T cr, where the metallic matrix began to yield macroscopically due to internal thermal stresses. For temperatures higher than T cr the thermal strains of MMCs showed a marked hysteresis during heating/cooling cycles due to the elasto-plastic response of the metallic matrix. In this temperature range, the thermal expansion curves deviated appreciably from linearity and the planar (in the plane of fibers) and transverse (normal to the plane of fibers) responses were very different: while the planar CTE was strongly reduced, the transverse CTE increased sharply with temperature, being even larger than the CTE of the unreinforced alloy. Thermal cycling produced a net dimensional change of composites during the first 2-3 cycles but, on the subsequent cycles, the permanent deformation disappeared almost completely and the successive thermal expansion curves were identical. Experimental results were compared to the theoretical predictions of an analytical model based on the Eshelby's equivalent inclusion method, and an excellent agreement was obtained.

Temperature dependent strength analysis of short fiber reinforced Al–Si metal matrix composites

Abstract Metal matrix composites (MMCs) were produced by a pressure infiltration technique, using Saffil ( δ -Al 2 O 3 ) alumina short fiber preforms as the reinforcement, and the alloy Al–12 wt% Si (LM 13) as the matrix material. The matrix alloy and the composites were subjected to a standard T6 heat treatment and consequently tensile tested. The room temperature strength of the composites were seen to increase up to 15 vol.% fiber and then deviated sharply from the linear behavior and decrease continuously as the fiber volume increased. As the test temperature was raised, all composites showed excellent retention of strength up to 300°C. Furthermore, the experimental results of tensile strength were compared to a modified rule of mixtures (ROM). The high temperature strength analysis showed that the strength of planar-randomly oriented short fiber reinforced material can be explained through combined effects of load transfer, dispersion strengthening, and dislocation strengthening. The reinforcement behavior of these type of composites is seen to be controlled by the elevated temperature properties of the matrix alloy. The theoretical tensile strength values, calculated with a temperature dependent modified rule of mixture equation, showed an excellent agreement with experimental data at room temperature and also at elevated temperatures of up to about 200°C.

Modelling of infiltration of molten metal in fibrous preform by centrifugal force

Infiltration kinetics of molten metal in fibrous preforms by centrifugal force is discussed theoretically. The relationship between the location of infiltration front and time is introduced for three major types of centrifugal casting processes. By the relationship, pressure distribution curves in the preform are also obtained. Some calculated examples are shown for the infiltration of molten aluminum into an alumina short fiber preform. If the speed of revolution is slightly higher than the minimum value determined by threshold pressure, infiltration is continuous. Since the second derivative of the pressure distribution curves in the infiltrated region is always positive and proportional to angular velocity in the centrifugal force field, the pressure curves are convex toward low pressure. When the surface pressure of the preform is low enough or the speed of revolution is high, the region having lower pressure than the threshold pressure appears in the infiltrated region. These results are compared with experimental data from references and by the authors.

Fabrication of gradient distribution alumina short fibre reinforced aluminium alloy

Gradient distribution alumina short fibre reinforced 6061 aluminium alloy have been fabricated by taking advantage of preform compressive deformation during squeeze casting. Pressure was applied mechanically by a punch. Velocity of the punch, pre-heat temperature of the preforms and pouring temperature were controlled during the infiltration of molten 6061 alloy into alumina short fibre preforms. The distribution of hardness along the infiltration direction in the composites was measured and the distribution of volume fraction along the infiltration direction was calculated by the hardness. Velocity of the inflow, pre-heat temperature of the preform, pouring temperature of the molten metal, binder content of the preform and volume fraction of fibres, all have a very great effect on the gradient distribution of alumina short fibres in the aluminium alloy composites.

Process, microstructure and properties of squeeze-cast short-carbon-fibre-reinforced aluminium-matrix composites

Two types of high-modulus short-carbon-fibre-reinforced commercially pure aluminium-matrix composites were fabricated in-house using a home-made squeeze caster. The type-I composites were fabricated from short-fibre preforms in which fibres exist as dispersed bundles. The type-II composites were fabricated from preforms in which individual fibres were uniformly dispersed. The detailed processes are described in the text. A three-point-bending strength of higher than 200 M Pa was obtained for the type-1 composite with 17 vol% of fibre. When more fibre was incorporated, both the strength and the ductility decreased due to inadequate infiltration. However, a bending strength of greater than 240 MPa was recorded on a hot-rolled type-I composite with a fibre content as high as 28 vol%. This significant improvement in the mechanical properties is explained by a hot-rolling-inducedvoid-healing effect. The type-II composites, with lower fibre volume fractions than those of the type-I due to their different preforms, exhibited bending strengths up to 166 MPa. Scanning electron microscopy fractography shows that the two types of composites fracture in distinctive manners. Transmission electron microscopy results featured thermal-stress-induced dislocations at carbon-aluminium interfaces as well as submicrometre-sized aluminium carbide, the reaction product, which nucleated from the interface and grew into the matrix interior.

Electrostatic orientation of ceramic short fibers in liquid

An electrostatic method of fabricating a unidirectionally-oriented ceramic short fiber preform has been developed for use in the production of Fiber-Reinforced Metals. In this process, alumina short fibers dispersed in insulating liquid (CFC-113) containing a small amount of surfactant are polarized by application of dc field and electostacically aligned in the field direction. In this study, theoretical treatment of the electrostatic orientation of fiber under an electric field is first presented, then experimental observations of fiber motion in the field is made. The speed of fiber orientation is predicted by the equation of motion based on the polarization model of fiber approximated to a prolate ellipsoid. Experimental results show that the time constant of polarization due to surface conduction is sufficiently smaller than that of mechanical orientation of fiber. Addition of surfactant increases the liquid conductivity, and the field induced polarization of fiber depends on the ratio of the fiber conductivity equivalent to its surface conductivity to the liquid conductivity. The final values of polarized charge and of the force acting on one end of oriented fibers are estimated.

4852630 Short fiber preform, method of making it, and composite material manufactured from it : Kane Hamajima, Atsuo Tanaka, Masahiro Kubo, Tadashi Dohnomoto, Toyota, Japan assigned to Toyota Jidosha Kabushiki Kaisha

4852630 Short fiber preform, method of making it, and composite material manufactured from it : Kane Hamajima, Atsuo Tanaka, Masahiro Kubo, Tadashi Dohnomoto, Toyota, Japan assigned to Toyota Jidosha Kabushiki Kaisha