Compressive Strength Of Composites Research Articles

Review on the Mesomechanical Compressive Strength Model of Single-Directional Fiber Composites

The longitudinal compression strength of single-directional fiber-reinforced composite is related to many factors, such as the mechanical properties, the fractions of components, and the distribution of flaws. There are no abroad and uniform opinions about its longitudinal compressing break mechanism yet. Thus, a review of recent developments in the compression strength mesomechanical forecasting models of single-directional fiber-reinforced composites is presented. The damage mechanisms based by these models and the affecting factors considered in them are analyzed. The application conditions of each models are shown, and the model choosing method of combining experiment and theoretical analyze is suggested.

Review on the Mesomechanical Compressive Strength Model of Single-Directional Fiber Composites

The longitudinal compression strength of single-directional fiber-reinforced composite is related to many factors, such as the mechanical properties, the fractions of components, and the distribution of flaws. There are no abroad and uniform opinions about its longitudinal compressing break mechanism yet. Thus, a review of recent developments in the compression strength mesomechanical forecasting models of single-directional fiber-reinforced composites is presented. The damage mechanisms based by these models and the affecting factors considered in them are analyzed. The application conditions of each models are shown, and the model choosing method of combining experiment and theoretical analyze is suggested.

Electrical, thermal, and mechanical properties of Cu50Zr40Ti10 bulk amorphous composite

Abstract Cu 50 Zr 40 Ti 10 amorphous alloy powder and Cu 60 Zr 30 Ti 10 plate-like ultrafine alloy powder were prepared by gas-atomization and ball-milling methods, respectively. Cu 50 Zr 40 Ti 10 bulk amorphous alloy (BAA) composites reinforced by Cu 60 Zr 30 Ti 10 alloy powder were fabricated by hot pressing method. The matrix of the composites remains a fully amorphous phase after consolidation process. The Cu 50 Zr 40 Ti 10 BAA composites exhibit improved plasticity and dramatically improved electrical and thermal properties by the Cu 60 Zr 30 Ti 10 powder addition. However, the density and compression strength of the BAA composites decrease with the increasing amount of Cu 60 Zr 30 Ti 10 alloy powder.

Porous polyurethane composites with natural fibres

In the work the methodology and results of the investigations that concern rigid polyurethane foams modified with natural fibres and oil-based polyol are presented. The goal of the investigations was to obtain the cellular, polyurethane composites with the heat insulating and mechanical properties similar or better as in the case of the reference material. The obtained polyurethane composites had apparent densities about 40 kg/m 3. The modified composites contained the considerable part of biodegradable components on the base of renewable raw materials. The influence of the rapeseed oil-based polyol, flax and hemp fibres of different length on the cell structure, closed cells content, apparent density, thermal conductivity and compression strength of the rigid polyurethane composites are analyzed. In the case of application of fibre in the amount of 5% php (per hundred polyols) the foam composites with the highest values of compressive strength and the lowest thermal conductivity were obtained.

Preparation and properties of octacalcium phosphate–polyhydroxybutyrate thin film composites

The octacalcium phosphate–poly(3-hydroxybutyrate) (OCP–PHB) thin film powder composites were prepared by the precipitation of PHB from OCP–PHB from chloroform suspension. The morphology of powder OCP–PHB composite and microstructure of composite pellets were observed by scanning electron microscopy. The presence of PHB thin film on OCP particles and the formation of new calcium phosphate phase after soaking of compact in simulated body fluid (SBF) at 37°C for 2weeks were verified. Phase composition was analysed by X-ray diffraction analysis and IR spectroscopy. The composite pellets were resistant to disintegration after immersion into SBF and the compressive strength of composite was around 6MPa.

The effect of elevated temperature curing treatment on the compression strength of composites with polyester resin matrix and quartz filler

In this study, polyester resin and quartz are used as binding and filling materials. In accordance with different aggregate diagrams and binding rates designed on standard cement concrete grain-size curves, polymer concrete composite samples were prepared. Such samples were initially solidified at room temperature and then placed in an oven at 50 °C, 75 °C and 100 °C. The samples were then compression tested. As a result of the compression strength determination and analysis, it is observed that the elevated temperature treatments increased the compression strength. The highest compression strength is obtained in a temperature of 75 °C.

Hydroxyapatite Nano-Barium-Strontium-Titaniumoxide Composites

The aim of this study is to produce and to investigate the mechanical and microstructural properties of composite materials made of hydroxyapatite, obtained from natural bovine bone and nano barium strontium titanium oxide (5 and 10 wt%). Compositions were mechanical alloyed and compacted to pellets. The samples were subjected to sintering at different temperatures between 1000oC and 1300oC. Compression strength, Vickers microhardness as well as density were measured. SEM and X-ray diffraction studies were also conducted. With increasing sintering temperature, microhardness, compression strength and density of composites increased. With increasing addition of nano barium strontium titanium oxide (BST) to bovine hydroxyapatite (BHA), microhardness values of composites decreased at all sintering temperatures, but compression strength and density values of composites showed different tendency. Compression strengths of BHA-composites at low sintering temperatures were nearly the same, but their compression strengths at high sintering temperatures decreased with increasing nano BST addition. The best mechanical properties were obtained at 1300°C sintering temperature with BHA-5wt% nano BST. Microhardness and compression strengths values of these nano–oxide composites are generally higher than that BHA-composites produced by traditional methods. Adding of nano-oxides to BHA could be a valuable method to produce rigid and high load carrying ability when compared with BHA-composites produced by conventional methods. Nano-HA and nano-oxides composites could be even better. Those nano-nano studies are still in progress.

Effects of addition of NH 4HCO 3 on pore characteristics and compressive properties of porous Ti-10%Mg composites

Porous Ti-Mg composites were successfully fabricated through powder metallurgy processing with ammonium hydrogen carbonate (NH 4HCO 3) as a space-holder. The effects of NH 4HCO 3 on properties of porous composites were comprehensively investigated. The pore characteristics and compressive properties of the specimens were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results show that the porosity of the porous composites can be tailored effectively by changing the amount of NH 4HCO 3 added, and the use of NH 4HCO 3 has no influence on the microstructure and phase constituents of the Ti-10%Mg porous composites. The open porosity and compressive strength as well as compressive elastic modulus vary with the adding amount and particle size of NH 4HCO 3. When the mass fraction of NH 4HCO 3 added is 25%, elastic modulus and compressive strength of composites with porosity of around 50% are found to be similar to those of human bone.

MODIFICATION OF PROPERTIES OF STRUCTURAL LIGHTWEIGHT CONCRETE WITH STEEL FIBRES / LENGVOJO BETONO SAVYBIŲ MODIFIKAVIMAS PLIENINĖMIS FIBROMIS

Structural lightweight aggregate concrete (SLWAC) is an alternative building material to normal-weight one, due to its ability to reach a relatively high compressive strength at still significantly lower density. Nevertheless, the application of lightweight aggregate instead of normal-weight one to concrete must result in deterioration of some characteristics of the composite. One of the methods of improving SLWAC properties is incorporation of fibers into concrete. This paper focuses on the influence of steel fibres on modification of properties of structural lightweight concrete with sintered fly ash aggregate. Two different concrete mixtures, producing various levels of matured composite density and compressive strength, were modified with three dosages of fibers: 30, 45 and 60 kg/m3. The applied amounts did not result in significant deterioration of the rheological parameters of concrete mixtures. Despite relatively low volume content of fibres, a considerable increase of flexural and tensile splitting strength was observed. Fibres also improved concrete shrinkage as well as post-peak deformability in uni-axial compression. The effect of steel addition on compressive strength proved to be dependent on specimen type. Nevertheless, it was not as crucial as in the case of the above characteristics. However, the modulus of elasticity of SLWAC was not affected by fibre addition. Santrauka Konstrukcinis su lengvaisiais užpildais betonas (SLWAC) yra normalaus svorio statybinių medžiagų alternatyva, turinti mažesnį tankį ir gebėjimą pasiekti gana didelį gniuždomąjį stiprį. Nepaisant to, lengvieji užpildai, naudojami vietoj normalaus svorio užpildų, realiai gali pabloginti kai kurias kompozito savybes. Vienas iš lengvojo betono SLWAC savybių tobulinimo būdų yra plieninių fibrų įterpimas į betono sudėtį. Šiame darbe aptariamas plieninių fibrų poveikis konstrukcinio lengvojo betono su lakiaisiais pelenais savybėms. Tikslui pasiekti buvo parinktos pagal tankį ir gniuždomąjį stiprį dvi skirtingos betono sudėtys su skirtingais (30, 45 ir 60 kg/m3) plieninių fibrų tankiais. Paruošti bandiniai buvo naudoti gniuždomajam stipriui ir kitoms savybėms nustatyti. Tyrimų rezultatai parodė, kad plieninių fibrų priedas nepablogino reologinių betono mišinio rodiklių. Nepaisant palyginti mažo fibrų kiekio, labai padidėjo bandinių lenkiamasis ir tempiamasis stipris. Fibros taip pat pagerino deformacines betono savybes. Gauto kompozito gniuždomasis stipris iš dalies priklausė nuo naudojamų plieninių fibrų charakteristikų. Tačiau plieninių fibrų priedas nepakeitė SLWAC tamprumo modulio.

Mechanical properties of spacer fabric-reinforced composites knitted from glass yarn

In this study, to investigate the tensile, compression, and impact strengths of weft-knitted spacer fabric-reinforced composites made from glass yarn, first the glass yarn was knitted on industrial flat knitting machine and two types of spacer preforms were produced. Then, mechanical tests were applied to examine the strengths of the composites manufactured from spacer preforms. As a result, it is concluded that making tuck stitches in short and long needles improves locking of upper and lower layers of the spacer fabric; also the minority of crossover points in the second type of the spacer fabric generate a very stiff and high strength spacer fabric preform.

On the Distribution of Delamination in Composite Structures and Compressive Strength Prediction for Laminates with Embedded Delaminations

In this study, large numbers of aircraft composite structures were inspected, and the distribution of delamination sizes and though thickness positions in the composite laminates are investigated. An experiment is conducted to probe into the influence of delamination sizes and through thickness positions on the compressive strengths of laminates with single embedded circular delamination, with the most dangerous delamination sizes and positions defined from the distribution. Furthermore, a shell model is established for compressive strength prediction, with delamination propagation assessed using a mixed mode criterion. The finite element (FE) prediction comes out to be in good agreement with the experimental measurements, for the predicted compressive strengths stand within 10% error of experimental results. It was observed that the compressive strength was highly influenced by the delamination size, while the through thickness position of delamination did not have significant effect on the compressive strength.

A unified formulation for hollow and solid concrete-filled steel tube columns under axial compression

On the basis of the theory of elasticity, a unified formulation is proposed in this paper to predict the composite compressive strength of circular concrete-filled steel tube (CCFST) columns. The formula is obtained from the analytic solution of an elastic composite cylinder under axial compression. The formula is further calibrated by introducing a number of correlation coefficients that are validated by test results. Furthermore, the stability factor of CCFST long columns under axial compression is derived on the basis of the Perry–Robertson formula. The newly derived formulas of stability bearing capacity are applicable for both hollow and solid CCFST columns, which is again validated through comparisons with experimental results. One of the important features of the new formulas is that they provide a unified formulation for both hollow and solid CCFST columns that relates the compressive strength or the stability capacity of a CCFST column and a series of design parameters.

Numerical Simulation of Matrix Reinforced Composite Materials Subjected to Compression Loads

This paper reviews the most common formulations to obtain the compression strength of long fiber composites due to fiber buckling. This failure mode was first studied by Rosen (Fibre Composite Materials, pp. 37–45, 1965) who defined two different fiber buckling modes, extensional and transverse. Further studies improved the first model proposed by Rosen by defining with more accuracy the mechanics of the problem. Although each formulation use a different approach to solve the problem, all of them agree in the dependence of fiber buckling on three main parameters: matrix shear strength, fiber initial misalignments and volumetric participation of the fibers in the composite. Once having described the different approaches used, and the parameters on which they depend, this paper describes a new formulation capable of obtaining the compression strength of composites taking into account the fiber buckling phenomenon. This formulation uses the serial/parallel mixing theory developed by Rastellini et al. (Comput. Struct. 86(9):879–896, 2008) to simulate the composite, and takes advantage of knowing the mechanical performance of the composite constituents to simulate the fiber buckling phenomenon. This is done with an homogenization procedure. It consists in introducing the interaction between fibers and matrix into their respective constitutive equations. The interaction between fiber and matrix takes into account fiber initial misalignments, its volumetric participation and the mechanical properties of both constituents. The new formulation proposed is implemented in a finite element code, taking into account that fibers can have different misalignment levels, and that the composite behaves differently if it is under tensile or compression forces. The mechanical performance of the formulation proposed is studied with several finite element simulations of compressed composites. Finally, the correctness of the formulation is proved by comparing the numerical results with the experimental tests provided by Barbero and Tomblin (Int. J. Solids Struct. 33(29):4379–4393, 1996), Tomblin et al. (Int. J. Solids Struct. 34(13):1667–1679, 1997).

Microstructure–properties relationship in ceramic–elastomer composites with 3D connectivity of phases

The ceramic–elastomer composites with 3D phase connectivity were tested under compressive loads. Such composites exhibit high initial strength and stiffness with the ability to sustain large deformations. Samples of the composites were made of porous SiO2 ceramic matrix infiltrated by polyurethane elastomer. The ceramic matrix preforms used differed in the porosity and three different composite microstructures have been obtained. Selected parameters of microstructure composites were evaluated using image analysis. The compressive strength and capacity for energy absorption are characterized under various strain rates (0.001–235 s−1). It was found that stress–strain characteristic depends on the strain rate and the specific interface area (Sv). Pore size and the specific interface area have a strong effect on the compressive strength of composites and these parameters can be used for tailoring their mechanical properties. The acoustic emission was applied to identify stages in the process of microstructure damage during compression. The interpretation of damage stages was proposed, which also explains the character of the stress–strain curves.

Characterization of compression strength of granite-epoxy composites using design of experiments

This paper presents a processing study of the polymer matrix composite (PMC) developed with an epoxy polymeric matrix reinforced with particulate ceramic granite. This PMC composite has been reported to be used as structural parts of machine tools and Coordinate Measuring Machines due to its superior vibration damping characteristics and reduced processing cycle over cast iron. The investigated processing variables were epoxy content and particle size and the mechanical characterization was carried out by compressive tests. Rejects of granite with particle size smaller than 500 µm were prepared by crushing, milling and classification operations. The powder was mixed with different compositions of epoxy resin, between 15 and 20% in weight. An experiment was planned and executed according to the Factorial design technique using two variables at two levels. The obtained cylindrical samples were submitted to compressive strength tests and the results showed a maximum resistance of 114.23 MPa at 20 wt. (%) epoxy, value close to that of the literature.

Poly(propylene fumarate)/(calcium sulphate/β-tricalcium phosphate) composites: Preparation, characterization and in vitro degradation

This study aimed to prepare a poly(propylene fumarate)/(calcium sulphate/β-tricalcium phosphate) (PPF/(CaSO4/β-TCP)) composite. We first examined the effects of varying the molecular weight of PPF and the N-vinyl pyrrolidinone (NVP) to PPF ratio on the maximum cross-linking temperature and the composite compressive strength and modulus. Then the in vitro biodegradation behaviour of PPF/(CaSO4/β-TCP) composites was investigated. The effects of varying the molecular weight of PPF, the NVP/PPF ratio and the CaSO4/β-TCP molar ratio on the weight loss and the composite compressive strength and modulus were examined. The cross-linking temperature, which increased with increasing molecular weight of PPF and NVP/PPF ratio, ranged from 41 to 43°C for all formulations. The mechanical properties were increased by a decrease in the NVP/PPF ratio. For all formulations, the compressive strength values fell between 12 and 62MPa, while the compressive modulus values fell between 290 and 1149MPa. The weight loss decreased either with increasing molecular weight of PPF or with decreasing NVP/PPF ratio and CaSO4/β-TCP molar ratio during degradation. The compressive strength and modulus increased with decreasing NVP/PPF ratio or decreasing CaSO4/β-TCP ratio. The greatest weight loss over 6 weeks was 14.72%. For all formulations, the compressive modulus values fell between 57 and 712MPa and the compressive strength fell between 0.5 and 21MPa throughout 6 weeks degradation. Scanning electron microscopy and X-ray diffraction analysis of the PPF/(CaSO4/β-TCP) composites demonstrated that hydroxyapatite was deposited on the surface of CaSO4/β-TCP granules during degradation.

Hydroxyapatite containing superporous hydrogel composites: synthesis and in-vitro characterization

The synthesis of an acrylamide-based superporous hydrogel composite (SPHC) with hydroxyapatite (HA) was realized by solution polymerization technique. The characterization studies were performed by FTIR studies, determination of swelling kinetics, measurement of mechanical properties, SEM/EDAX studies and cytocompatibility tests. The FTIR and EDAX studies revealed the incorporation of HA in superporous hydrogel (SPH) structure. The results obtained from swelling experiments showed that, although the extent of swelling was decreased after incorporation of HA in SPH structure, the time to reach the equilibrium swelling was not affected for SPHC. This result indicated that, the presence of HA did not block the capillary channels and the interconnected pore structure was maintained which were consistent with the images obtained from SEM photographs. The results obtained from mechanical tests showed that, in the presence of HA, the compression strength of the hydrogel composite was improved significantly when compared to SPH structure. The compressive modulus for the SPHC increased to 6.59 +/- 0.35 N/mm(2) whereas it was 0.63 +/- 0.04 N/mm(2) for the SPH. The cytocompatibility test which was performed by using L929 fibroblasts showed that both the SPH and SPHC materials were cytocompatible towards fibroblasts. The synthesized superporous hydrogel composite possesses suitable properties especially for bone tissue engineering applications and shall be considered as a novel scaffold.

GRAFTING MMA ONTO FLAX UNDER THE INFLUENCE OF MICROWAVE RADIATION AND THE USE OF FLAX-g-POLY(MMA) IN PREPARING PF COMPOSITES

Abstract This paper deals with the graft co-polymerisation of methylmethacrylate (MMA) onto flax fibre under the influence of microwave radiation (MWR). The graft co-polymers are characterised by FTIR spectroscopy, scanning electron microscopy (SEM), thermal analysis (TGA/DTA) and X-ray diffraction (XRD). Graft co-polymers are subjected to the evaluation of some physical, chemical and mechanical properties. Graft co-polymers thus prepared are used in the preparation of phenol-formaldehyde composites. Wear resistance, tensile strength and compressive strength of composites are measured, and it is found that composites reinforced with flax-g-poly(MMA) showed better mechanical properties in comparison to composites reinforced with raw flax.

The structural safety of hollow concrete-filled circular steel members

The resistance of new type of hollow concrete-filled circular steel tubular members under axial compression is considered. The effect of interaction between steel tube and spun concrete core contact surfaces on composite member compressive strength is analysed. The experimental values of member’s resistance and its mechanical model uncertainty are presented. The necessity to assess the structural safety of precast members exposed to actions in pre-use and use working lives is discussed. Peculiarities of the mechanical model describing the safety margin of ageing and not ageing compression members are analysed. The probability-based assessment of structural safety of particular members (compressive cross-sections) subjected to extreme loadings is presented and illustrated by numerical example.

Sintering Effect on Mechanical Properties of Composites of Hydroxyapatite Lanthanum Oxide (HA-La<sub>2</sub>O<sub>3</sub>)

Composites of calcinated bovine bone derived hydroxyapatite (HA) with 0.25, 0.5, 1, and 2 wt % La2O3 were prepared by sintering. The experimental results indicated that compression strength and microhardness of HA-La2O3 composites increase when the content of La2O3 and sintering temperature increase. The best mechanical properties were achieved after sintering at 1300°C. The results are in agreement with densification measurements and microstructure analysis.