Compressive Strength Of Composites Research Articles

A novel cement-based auxetic foam composite: Experimental study

Auxetic foam materials contract (expand) laterally under uniaxial compressive (tensile) load. Due to superior characteristics of auxetic foam, e.g., shear resistance and in-plane indentation resistance, studies of auxetic foam composites have been increasing in recent years. In this paper, a novel cement-based auxetic foam composite is designed, fabricated and experimentally investigated. The influence of foam hole density, mass fraction and age on the flexural and compressive strength of the composite is analyzed. The failure modes and crack development of the specimen are examined. It is found that the flexural and compressive strength of composite are improved at the curing age of 7 and 14 days, and reduced at the curing age of 28 days with the incorporation of auxetic foam. And the flexural compression ratio of the composite is greater than that of matrix material. The integrity of the specimen is preserved during the compression failure process of cement-based auxetic foam composites. It is indicated that the incorporation of auxetic foam improves the toughness and deformation behavior of composites.

A real micro-structural model to simulate the transversal compression behaviors of unidirectional composites based on the μ-CT detection

In this paper, the microstructural model of the unidirectional (UD) composite was firstly built based on a series of computed tomography (CT) images captured with the micro-CT (μ-CT) technique. During the modeling process, a fast and simple algorithm based on the image processing technique was developed to find out the centroids of fibers in CT images. The validity of the microstructural model was then verified by comparing it with some other ideal models and experimental results. The verification results indicated the fiber accumulated array is responsible for the compression modulus, strength, and failure model of UD composite. Besides, the resin bubble has the most significant effect on the transversal compression behavior of UD composite. The idea of creating the real microstructural model for UD composite can also be used for other types of composites to improve the precision of the related numerical models.

Characterization and Evaluation of Mechanical Properties of Al-Zn Based Hybrid Metal Matrix Composites

Hybrid aluminium matrix composites are preferred for structural applications due to their tailored material properties. In the current study, aluminium-7029 alloy with boron carbide (5, 10, and 15 wt%) and a constant weight percentage of graphite (5 wt%) were produced by the stir casting route. Scanning Electron Microscope and X-Ray Diffraction were used to characterize the composites. The cast alloy and hybrid composites were evaluated for physical (density and porosity) and mechanical (hardness, tensile, compressive and impact) properties by experimental and statistical methods. The porosity of the cast samples was minimal (<5%) and the hybrid composite weight decreased (2.4%) with the increase of reinforcements as revealed by the density test. Al7029/15wt%B4C/5wt%Gr (sample C3) hybrid composite hardness (126 BHN) and compressive strength (586.841 MPa) were found to be the best to get the better property with more reinforcement. Tensile (253.455 MPa) and impact strength (7 J) were the highest for the Al7029/5wt%B4C/5wt%Gr (sample C1) hybrid composite. Results obtained by a regression model developed using MINITAB were in good agreement with experimental values. The additions of B4C and Gr were found to improve mechanical properties significantly, as confirmed by analysis of variance.

Influences of SiC infiltration and coating on compressive mechanical behaviours of 2D C/SiC composites up to 1600 °C at wide-ranging strain rates

The influences of the SiC infiltration and coating on the compressive mechanical behaviours of 2D C/SiC composites were determined up to 1600 °C at 0.001 and 1000/s strain rates in argon and air. In addition, the failure mechanisms responsible for the compressive mechanical behaviours were elucidated through in-situ observation and micro-analysis-based methods. The 2D C/SiC composite compressive strength was highly sensitive to temperature, loading rate, and oxidation, and was enhanced by the change in the thermal residual stress and decreased by oxidation. In argon, because of the extra infiltrated SiC matrix, SiC treated 2D C/SiC specimens exhibited higher compressive strengths and lower strain rate sensitivity factors than SiC untreated 2D C/SiC specimens. The SiC coating effectively improved the oxidation resistance of the 2D C/SiC composites in air, regardless of the temperature, strain rate, and oxidative damage-which depends on SiC coating, strain rate, and temperature.

Test research on hydration process of cement-iron tailings powder composite cementitious materials

Cement-based composite cementitious materials (CCMs) were prepared using mechanically ground iron tailings powder (ITP) to partially replace cement. The hydration heat, non-evaporable water (n-EW) content, Ca(OH)2 (CH) content, ITP reaction degree, and mortar compressive strength were tested to understand the hydration of the CCMs. The test results show that the addition of ITP postpones the emergence of the hydration exothermic peak and reduces the hydration cumulative heat release and exothermic rate. Moreover, the n-EW and CH content of the CCM paste at the specified age are lower than those of the cement paste, and the reaction degree of ITP increases with aging. However, it does not exceed 40% at 90d age. Compared with the cement mortar, the composite mortar compressive strength decreases to different degrees, and the rate of decrease declines with age. Early-age high-temperature curing is beneficial to the early hydration of the CCMs. However, it has a lesser or a negative influence on the middle and late hydration. This study shows that the supplementary cementitious effect of mechanically ground ITP changes the hydration process of cement-based cementitious materials, which in turn affects their performance. The result of each test correlates well, laying a reliable foundation for revealing the hydration mechanism of cement-ITP CCMs.

Improved composite open-hole compression strength and trade-off with manufacturability controlled by stacking sequence effect and non-standard ply angles

The design of composite laminates requires consideration of part strength and manufacturability, both of which are controlled by ply angle and stacking sequence. This paper studies the open-hole compression strength and forming compatibility of laminates designed with standard angle (SA) and non-standard ply angle (NSA) layups using four different stacking sequence patterns. When increasing interply ply angle differences to provide greater interply lock-up, experimental test results show that dispersed stacking sequences improve failure strength of NSA laminates by up to 36%. Dispersed stacking patterns allow NSA laminates to consistently outperform reference SA laminates with increased failure strengths of up to 17%, indicating that this alternative design may produce stronger structural components. Results for stacking sequences of NSA laminates also reflect an inverse relationship between failure strength and formability . This implies an underlying trade-off between structural strength and manufacturing compatibility, which is worth considering when designing laminates for complex geometries. • Dispersed layups improve open-hole compression strength of non-standard angle laminates by up to 36%. • Non-standard angle laminates with dispersed layups can outperform standard angle laminates on open-hole compression strength by up to 17%. • Results show a trade-off between structural strength and manufacturing compatibility controlled by stacking sequence.

Mechanical characterization of areca fine fiber fabric (AFFF) reinforced epoxy composites

As the population grows, natural fibers are being used more frequently; as a result the use of natural fibers and agricultural waste has increased. Agricultural wastes, such as: arecanut husk fiber, banana fiber, and bamboo fiber, can be used to produce composite building materials. Arecanut husk fiber is the most abundantly available natural fiber. Arecanut fine fiber fabric (AFFF) is obtained from the arecanut shell. AFFF is broadly applicable in a variety of industries, including construction, marine structure, automobile, and aircraft. The current research focuses on the mechanical characteristics of composite panels, AFFF-mat preparation, and composite panel casting. A mat is prepared by a fine fiber treated with 6% of sodium hydroxide (NaOH). The composite panel used in this study was made by combining AFFF-mat and epoxy resin with hardener by hand lay-up method. The tensile and compression tests were conducted to investigate the mechanical properties of AFFF. SEM analysis was conducted to examine the failure of composite elements. The tensile and compression strength of composites obtained was 10.82 MPa and 55.614 MPa respectively. The average Young’s modulus obtained for tensile and compression test specimens were 4.98 GPa and 7.675 GPa respectively.

Effects of deposition - strategy - induced raster gaps and infill voids on the compressive strength of 3D printed isogrid structures

Additive Manufacturing (AM) parts are attractive for many applications. AM can produce parts of complex geometries in small batches with short lead times in a wide range of materials. While parts are commonly used in non-load bearing functions, improving mechanical properties can help expand their use in engineering applications. This work evaluates the effects that AM process conditions have on part strength. The relationship between design characteristics and path planning induced imperfections is discussed. The effects that raster gaps and internal voids have on the compressive strength of composites are analyzed based on the results of compressive tests and computer simulations.

Modified Synthesis and Physicochemical Characterization of a Bioglass-Based Composite for Guided Bone Regeneration.

Objectives Bioglass composites and polymers are materials of great interest for the medical and dental areas due to their properties, combining the bioactivity of ceramic materials and the mechanical properties of polymers. The purpose of the present study was to develop and to characterize the physicochemical and morphological properties an experimental bioglass-based ternary composite composed associated with sodium carboxymethylcellulose (Na-CMC) and polyvinyl alcohol (PVA). The compatibility of functional groups with bioglass was previously evaluated. The composite was then synthesized and evaluated in terms of morphology, elemental composition, compressive strength, porosity, and bioactivity. Materials and Methods The bioglass was previously synthesized using a sol-gel route and characterized using FTIR analysis to identify the functional groups. The bone graft composite was then synthesized associating the bioglass with PVA, surfactant Triton X, and Na-CMC. The composite was then morphologically characterized using SEM/EDS. The porosity of the composite was analyzed using µCT, which also provided the composite compression strength. The composite was then evaluated in terms of its bioactivity using SEM/EDS analyses after immersion in SBF for 12, 24, 48, and 72 h. Results FTIR analysis confirmed, among other components, the presence of Si–O–Ca and Si–O–Si bonds, compatible with bioglass. SEM analysis exhibited a composite with a porous structure without spikes. The elemental mapping confirmed the presence of Si, Ca, and P in the composite. µCT analysis demonstrated a porous structure with 42.67% of open pores and an average compression strength of 124.7 MPa. It has also demonstrated ionic changes in the composite surface after immersion in SBF, with increasing detection of Ca and P as a function of time, highlighting its chemical bioactivity. Conclusions It can be concluded that the proposed bioglass-based composite presents a three-dimensional, well-structured, chemically bioactive porous structure, mechanically resistant for being reinforced with polymeric phases, with promising results as a synthetic bone graft, which makes it suitable for guided bone regeneration.

Analysis of Number of Layers and Volume Fraction of Fiber Against Shock Load and Composite Compressive Strength Wind Turbine Propeller

The manufacture of wind turbine blades has a very high risk of failure, especially in the manufacturing section or in this case the material structure. If the structure of the propeller material is not able to withstand the very high pressure and air flow, it will result in the failure of the material structure when it is in use. For this reason, the purpose of this study was to determine the composition of composite materials that have high strength and toughness properties and are suitable for wind turbine propellers. The method used in this research is experimental. The independent variables include the number of layers and the volume fraction of straw fiber. The dependent variables are shock load and compressive strength. Each compression test specimen is made with a gauge length of 100mm, a width of 25mm, and a thickness of 2.5mm. While the impact test specimens are made equal to l25mm long, l2mm wide, l2mm high, and 2mm notch. The results showed that the bending strength of the straw fiber composite with 6 layers had an increasing trend as the number of layers increased. The highest bending strength with the number of piles of 6 layers and the lowest strength with the number of piles of 2 layers. In addition, the volume fraction is very influential on the bending stress of the straw composite matrix. It can be seen that the matrix with a volume fraction of 50% has the greatest bending stress in each number of layers, both 2, 4 and 6. For the impact test, it is found that the optimal number of layers occurs in the number of 2 layers with a volume fraction of 33%. The shock load tends to decrease. Meanwhile, based on the volume fraction, the larger the volume fraction, the smaller the shock load that can be received by the straw fiber composite material.

Effects of water hyacinth fiber size on sound absorption properties of advanced recycled palm oil-based polyurethane foam composite

This work aims to study the effects of the size of water hyacinth fiber (WHF) on the properties of a rigid sound absorption material from recycled palm oil-based polyurethane foam (PUF) Polyurethane Foam Compositecomposite. By fixing the NCO index of 100 with the WHF content of 1%wt, the sizes of WHF were varied from 80, 40, and 20 mesh to study the properties of PUF. The compression strength, optical microscopy, and sound absorption coefficient (SAC) of the PUF composite were tested. Reducing the mesh size of WHF from 80 to 20, the compression strength of PUF increased from 0.33 to 0.47 N/mm2. PUF with a WHF mesh size of 80 and a SAC value of 0.92 was suitable for sound absorption. Therefore, the PUF derived from both water hyacinth and used palm oil could be used as a promising alternative green material for sound absorption application.

Quantitative Identification of the Water Resistance Capacity of Composite Strata in Mining Coal Seam Floors

In coal seam mining, the water resistance of the floor composite strata is the key to determining whether water disaster occurs or not and to formulating water control countermeasures. Taking the Pingdingshan Coalfield No. 8 mine and Shoushan mine as the research objects, the thickness ratio of plastic brittle rock, core recovery rate, thickness of effective aquiclude, fault complexity, composite compressive strength, and equivalent water resistance coefficient were selected as the index factors. The comprehensive weight of each index factor was determined by using the entropy weight theory. The water resistance of the J16-17 coal seam floor composite rock in the study area was quantitatively evaluated using the fuzzy variable set mathematical model and was divided into five grades: extremely weak, weak, medium, strong, and very strong. The results show that the J16-17 coal floor composite rock layers with strong and very strong water resistance areas account for 23.64% of the total area, the medium areas account for 58.26%, and the weak and extremely weak areas account for 18.1%. These results provide support for the accurate assessment of water inrush hazards of a coal floor.

The Difference of Composite Resin Compressive Strength with Sidikalang Coffee Soaking

Composite resin is a caries filling material. Generally, dentists choose this type ofresin as a restoration material because this material has a high compressivestrength. There are several factors that influence the compressive strength ofcomposite resins, including beverages consumed such as coffee. This study aims todetermine the difference in the compressive strength of the composite resin withSidikalang coffee immersion in 9 hours, 27 hours and 54 hours immersion time.This type of research is experimental laboratories with posttest only control groupdesign. The research sample was composite resin measuring 8 mm in diameter and4 mm in height. The sample size is determined by the Federer formula and a totalsample of 24 was obtained for the four treatment groups. Measurement ofcompressive strength using a three-point bending tool on a universal testingmachine. Data were analyzed by using the oneway Anova test. Based on the resultsof the study, the average compressive strength of composite resin in the groupwithout immersion, 9 hours, 27 hours and 54 hours of immersion was 20.69 ± 0.84,18.94 ± 0.41, 14.36 ± 0.66 and 6.70 ± 0.48. From the results of the study it can beconcluded that the ads are a significant difference in the average compressivestrength of composite resin after immersion in Sidikalang coffee for 9 hours, 27hours and 54 hours.

In Vitro Evaluation of Calcium Phosphate Bone Cement Composite Hydrogel Beads of Cross-Linked Gelatin-Alginate with Gentamicin-Impregnated Porous Scaffold.

Calcium phosphate bone cement (CPC) is in the form of a paste, and its special advantage is that it can repair small and complex bone defects. In the case of open wounds, tissue debridement is necessary before tissue repair and the subsequent control of wound infection; therefore, CPC composite hydrogel beads containing antibiotics provide an excellent option to fill bone defects and deliver antibiotics locally for a long period. In this study, CPC was composited with the millimeter-sized spherical beads of cross-linked gelatin–alginate hydrogels at the different ratios of 0 (control), 12.5, 25, and 50 vol.%. The hydrogel was impregnated with gentamicin and characterized before compositing with CPC. The physicochemical properties, gentamicin release, antibacterial activity, biocompatibility, and mineralization of the CPC/hydrogel composites were characterized. The compressive strength of the CPC/hydrogel composites gradually decreased as the hydrogel content increased, and the compressive strength of composites containing gentamicin had the largest decrease. The working time and setting time of each group can be adjusted to 8 and 16 min, respectively, using a hardening solution to make the composite suitable for clinical use. The release of gentamicin before the hydrogel beads was composited with CPC varied greatly with immersion time. However, a stable controlled release effect was obtained in the CPC/gentamicin-impregnated hydrogel composite. The 50 vol.% hydrogel/CPC composite had the best antibacterial effect and no cytotoxicity but had reduced cell mineralization. Therefore, the optimal hydrogel beads content can be 25 vol.% to obtain a CPC/gentamicin-impregnated hydrogel composite with adequate strength, antibacterial activity, and bio-reactivity. This CPC/hydrogel containing gentamicin is expected to be used in clinical surgery in the future to accelerate bone regeneration and prevent prosthesis infection after surgery.

Effects of graphene nanosheets decorated by cerium stannate on the enhancement of flame retardancy and mechanical performances of flexible polyurethane foam composites

AbstractAs one of the most used polyurethane, flexible polyurethane foam (FPUF) still confronted highly flammable problems. However, current flame retardant employed in FPUF deteriorated the other utilization performances, such as mechanical properties. In this work, cerium stannate decorated graphene nanosheets (GNS@Ce2Sn2O7, GCSO) was prepared to fabricate flame retardant FPUF composites. Compared to pure FPUF, the tensile strength and average compression strength of FPUF composites accomplished 100 and 412% increase, respectively, while the average rebound was basically maintained. In contrast to pure FPUF, total heat release and total smoke production of FPUF composites displayed a 42.2 and 75.1% reduction, respectively. Furthermore, the released toxic gases (such as, CO2, CO and NOx) during combustion were greatly decreased. These results were due to the catalytic and barrier effect of GCSO promoting the formation a high‐quality char residue with a compact, intact and dense morphology. Therefore, it provides a facile method to fabricate FPUF composites with advanced comprehensive performance for the furniture field.

Mechanical behavior of carbonated MgO-based Engineered Cementitious Composite (ECC) after high temperatures exposure

Carbonated MgO-based Engineered Cementitious Composite (ECC) has ultrahigh tensile ductility and tight crack width control behavior. However, the expectation of improved fire-resistant has not been confirmed. This study explored the alterations to mechanical and microstructure characteristics of this material after exposure to temperatures up to 500 °C. Material mass loss, compressive strength, tensile strength, strain capacity, and matrix fracture toughness were measured. Scanning electron microscopy, mercury intrusion porosimetry, thermogravimetric analysis, and X-ray diffraction were used to probe the degradation of the cement matrix and fibers. The effect of elevated temperature on carbonated MgO-based ECC was further assessed via examination of the micromechanical behavior of the fiber-matrix. The objective of this research was to assess the performance of carbonated MgO-based ECC exposed to fire hazards. The tensile ductility of carbonated MgO-based ECC was found to be enhanced when exposed to ∼100 °C as compared with those at room temperature ∼20 °C. Further increase in exposure temperature, however, posed a negative impact on the composite compressive strength, ultimate tensile strength, and ability to control crack width. The results provide a useful database for further investigations into carbonated MgO-based ECC for fire safety enhancement.

Estimation of axial compressive strength of unidirectional carbon fiber reinforced plastic considering local fiber kinking

In this study, the global fiber kinking theory proposed by Budiansky and Fleck for the estimation of axial compressive strength of unidirectional carbon fiber reinforced plastic was modified for the localized fiber kinking problem. The deterministic mechanism of the compressive strength and kink-band width was interpreted using a graphical method. Carbon fiber reinforced plastic was manufactured from carbon fiber and epoxy matrix using prepreg and autoclave technology, and the axial compressive strength was measured. The nonlinear shear stress–strain curves of the composite and matrix were also measured using V-notched beam, in-plane shear, and torsion tests. The composite axial compressive strength and kink-band width were estimated based on the composite and matrix shear properties, respectively, and the estimated values were in good agreement with the experimental results.

Investigation the compression strength and thermal Properties of Composites Using Natural Additives with Epoxy

The main objective of this work was to investigate the effect of natural additives with an animal and vegetable source in the form of (short fibers and particle) on the mechanical and thermal properties for epoxy. (wood dust, date palm fiber, cow bones and sheep wool) were selected as natural additives with different weight ratios such as (%5,%15,%25) reinforcements for the epoxy matrix based composites, which were produced by the hand lay-up technique. mechanical test such compression strength and thermal properties such thermal conductivity were carried out according to ASTM standards to characterized these composites. It was found that the mechanical and thermal properties can be increased or decreased depending on the type of material additives, its origin, as well as the weight percentage used.

Hygrothermal Ageing Influence on BVI-Damaged Carbon/Epoxy Coupons under Compression Load.

Composite materials usage in several industrial fields is now widespread, and this leads to the necessity of overcoming issues that are still currently open. In the aeronautic industry, this is especially true for Barely Visible Impact Damage (BVID) and humidity uptake issues. BVID is the most insidious kind of impact damage, being rather common and not easily detectable. These, along with the ageing that a composite structure could face during its operative life, could be a cause of fatal failures. In this paper, the influence of water absorption on impacted specimens compressive residual strength was studied. Specimens were impacted using a modified Charpy pendulum. Two different locations were chosen for comparison: Near-Edge (NE) and Central (CI). Accelerated hygrothermal ageing was conducted on impacted and reference nonimpacted coupons, placing them in a water-filled jar at 70 °C. Compressive tests were performed in accordance with the Combined Loading Compression (CLC) test method. A Dynamic Mechanical Analysis (DMA) was performed as well. The results showed the influence of hygrothermal ageing, as expected. Nevertheless, the influence of impact location on compressive residual strength is not clearly noticeable in aged specimens, leading to the conclusion that hygrothermal ageing may have a greater effect on composite compressive strength than the analysed BVI damage.

Elastic Properties of Polymer Modified Steel Fibre Reinforced High Strength Concrete

The paper deals with the experimental and theoretical results of elastic constants of polymer modified high strength concrete with high fibre volume fraction. To evaluate elastic properties of this composite system, compressive and flexural strengths were obtained experimentally. Elastic properties such as modulus of elasticity and Poisson’s ratio are first obtained based on experimental results. Simplified equations based on micromechanics, and solid mechanics theories are utilized for the evaluation of elastic properties of polymer modified randomly oriented short steel fibre reinforced high strength concrete. The micromechanics equations for the modulus of elasticity and the Poisson’s ratio are based on the fibre volume fraction and the elastic moduli of the fibre and polymer modified concrete matrix. The existing empirical equations are also used to obtain elastic constants. These equations are applied in the full range of fiber volume fraction (1% to 10%). The comparison of experimental results with theoretical values shows the good agreement with each other. The novelty of the present paper is that the modulus of elasticity of this composite system is obtained experimentally using four point bending test and the Poisson’s ratio is obtained as a function of flexural and compressive strengths with excellent accuracy for the first time.