Compressive Strength Of Composites Research Articles

Effects of titanium carbide on modified magnesium oxysulfate cement: Microstructure and mechanical properties

This study explores the effects of micro and nano titanium carbide (TiC) on the properties of magnesium oxysulfate cement with dosages of 1–5%. The flexural and compressive strength of composites were 15–21 MPa and 82–95 MPa at 28d. TiC reduced brittleness by improving displacement and energy absorption capability to 82 % and 114 %. Curing age influenced flexural strength by increasing both displacement and energy absorption capability, but the compressive strength development depends primarily on energy absorption capability. The 517 phases in clusters or rings grown from interfaces with gels contributed to high strength of cement. The poor performance of composites containing 5% nano-TiC was attributed to the formation of magnesium hydroxide crystals. TiC decreased the water resistance due to the formation of long needle crystals. Carbonization did not reduce compressive strength statistically but weakened flexural strength by 18%–56 %. Evaluation based on 15 indicators concluded the optimal sample with 1 % nano-TiC, providing insights into the design of magnesium oxysulfate cement products with high performance.

Adaptive reuse of waste plastic as binders in composites for sustainable construction

Effective and efficient handling of solid waste remains a significant issue, particularly in low- and middle-income countries, and densely populated urban areas. Waste plastic is identified as a major contributor to solid waste streams. This study highlighted the viable reuse of waste Linear low-density polyethylene (LLDPE) plastic as a binder and full replacement for cement in composite blocks. An extrusion technique was adopted to melt the plastic and mix it with the sand fillers to create a homogenous waste plastic binder composite block. Composite block samples were produced at various mixture ratios of 1:1, 1:2, and 1:3 with waste plastic or cement as binder and sand as filler. The composite samples' compressive strength, flexural strength, tensile strength, UPV, thermal conductivity, skid resistance, Cantabro mass loss, and morphology were investigated. In addition, the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis of the composites were carried out. The results showed that composite blocks containing waste LLDPE plastic as binder exhibited lower compressive strength, higher flexural strength, and tensile strength, better thermal insulation, and abrasion resistance compared to composite blocks containing cement as binder. Meanwhile, the cement binder composite gave better skid resistance when the surface was wet than the waste plastic binder composite. However, the waste LLDPE plastic composite mixes considered gave compressive strength above 5 N/mm2, which is the minimum requirement for building bricks according to BS 3921: 1985.

An Experimental Study on the Performance of Materials for Repairing Cracks in Tunnel Linings under Erosive Environments

Addressing the current lining cracking problem in coastal tunnels, this paper independently introduces a novel type of repair material for tunnel lining cracks—the composite repair material consisting of waterborne epoxy resin and ultrafine cement (referred to as EC composite repair material). Through indoor testing, we have analyzed the change rule of the mass change rate, compressive strength, flexural strength, and chloride ion concentration of the repair material samples in erosive environments, with the dosage of each component in the EC composite repair material being varied. We have also investigated the working performance, mechanical properties, and microstructure of the repair material. The results of this study show that when the proportion of each component of ultrafine cement, waterborne epoxy resin, waterborne epoxy curing agent, waterborne polyurethane, defoamer, and water is 100:50:50:2.5:0.5:30, the performance of the EC composite repair material in a chloride ion-rich environment is optimal in all aspects. When the mixing ratio of each component of the EC composite repair material is as stated above, the repair material exhibits the best performance in a chloride ion erosion environment. With this ratio of components in the EC composite repair material, the fluidity, setting time, compressive strength, flexural strength, and bond strength of the repair material in a chloride ion erosion environment can meet the requirements of relevant specifications, and it is highly effective in repairing tunnel lining cracks. The polymeric film formed by the reaction between the waterborne epoxy resin emulsion and the curing agent fills the pores between the hydration products, resulting in a densely packed internal structure of EC composite repair material with enhanced erosion resistance, making it very suitable for repairing cracks in tunnel linings in erosive environments.

Optimization and Modelling of the Physical and Mechanical Properties of Grass Fiber Reinforced with Slag-Based Composites Using Response Surface Methodology.

The construction industry's high energy consumption and carbon emissions negatively impact the ecological environment; large-scale construction projects consume much energy and emit a significant amount of CO2 into the atmosphere. Statistics show that 30% of energy loss and 40% of solid waste in the construction industry are generated during construction. Therefore, reducing emissions during construction has significant research potential and value. Many scholars have recently studied eco-friendly building materials to facilitate the use of high-carbon emission materials like cement. Adding fibers to composite materials has become a research hotspot among these studies. Although adding fibers to composite materials has many advantages, it mainly reduces the compressive strength of the composite material. This research used the response surface methodology (RSM) to optimize the raw material ratios and thus improve the performance of plant fiber composite materials. Single-factor experiments were conducted to analyze the effects of grass size, grass content, and quicklime content on the composite materials' compressive strength, flexural strength, and water absorption. The influencing factors and levels for the response surface experiment were determined based on the results of the single-factor analysis. Using the response surface methodology (RSM), a second-order polynomial regression model was established to analyze the interaction effects of the three factors on the composite materials' compressive strength, flexural strength, and water absorption rate. The optimal ratio was determined: the optimized options for grass size, grass content, and quicklime content are 2.0 mm, 8.2 g, and 38 g, respectively. The actual values of compressive strength, flexural strength, and water absorption rate of the composite materials made according to the predicted ratio are 11.425 MPa, 2.145 MPa, and 21.89%, respectively, with a relative error of 8% between the actual and predicted values. X-ray diffraction and scanning electron microscopy were also used to reveal the factors contributing to the relatively high strength of the optimized samples.

Performance Comparison of Artificial Neural Network and Random Forest Models for Predicting the Compressive Strength of Fibre-Reinforced GGBS-Based Geopolymer Concrete Composites

Performance Comparison of Artificial Neural Network and Random Forest Models for Predicting the Compressive Strength of Fibre-Reinforced GGBS-Based Geopolymer Concrete Composites

Indirect prediction of graphene nanoplatelets-reinforced cementitious composites compressive strength by using machine learning approaches

Graphene nanoplatelets (GrNs) emerge as promising conductive fillers to significantly enhance the electrical conductivity and strength of cementitious composites, contributing to the development of highly efficient composites and the advancement of non-destructive structural health monitoring techniques. However, the complexities involved in these nanoscale cementitious composites are markedly intricate. Conventional regression models encounter limitations in fully understanding these intricate compositions. Thus, the current study employed four machine learning (ML) methods such as decision tree (DT), categorical boosting machine (CatBoost), adaptive neuro-fuzzy inference system (ANFIS), and light gradient boosting machine (LightGBM) to establish strong prediction models for compressive strength (CS) of graphene nanoplatelets-based materials. An extensive dataset containing 172 data points was gathered from published literature for model development. The majority portion (70%) of the database was utilized for training the model while 30% was used for validating the model efficacy on unseen data. Different metrics were employed to assess the performance of the established ML models. In addition, SHapley Additve explanation (SHAP) for model interpretability. The DT, CatBoost, LightGBM, and ANFIS models exhibited excellent prediction efficacy with R-values of 0.8708, 0.9999, 0.9043, and 0.8662, respectively. While all the suggested models demonstrated acceptable accuracy in predicting compressive strength, the CatBoost model exhibited exceptional prediction efficiency. Furthermore, the SHAP analysis provided that the thickness of GrN plays a pivotal role in GrNCC, significantly influencing CS and consequently exhibiting the highest SHAP value of + 9.39. The diameter of GrN, curing age, and w/c ratio are also prominent features in estimating the strength of graphene nanoplatelets-based cementitious materials. This research underscores the efficacy of ML methods in accurately forecasting the characteristics of concrete reinforced with graphene nanoplatelets, providing a swift and economical substitute for laborious experimental procedures. It is suggested that to improve the generalization of the study, more inputs with increased datasets should be considered in future studies.

Influence of Microstructure Randomness on the Shear Behaviour and Compressive Strength of Continuous Carbon Fibre Composites

Influence of Microstructure Randomness on the Shear Behaviour and Compressive Strength of Continuous Carbon Fibre Composites

Effect of Fiber Content on the Mechanical Properties of Jute Fiber Reinforced Perlite/Gypsum Composites

Fiber reinforcement is one of the ways for the improvement of the mechanical properties of composite materials. Previously, it was seen that the fiber content in composites played a vital role in the mechanical properties of fiber-reinforced composites. Considering the benefits of natural fiber, in this work, jute fiber reinforced perlite/gypsum composites were manufactured with five different fiber contents ranging from 2.41 % to 4.82 %. The ratios of gypsum to perlite and gypsum to water were kept constant, and only fiber content was varied. The compression and flexural tests were conducted to investigate the effect of jute fiber content on the mechanical properties of jute fiber-reinforced perlite/gypsum composites. Results showed that both the compressive and flexural properties were improved up to certain jute fiber content. The compressive strength, modulus, and energy absorption of the jute fiber-reinforced composite were found to be the maximum at 3.01 % fiber content. The compressive strength of the composite with 3.01 % jute fiber content was 35.23 % higher than the composite with 2.41 % fiber content. The flexural strength, modulus, and energy absorption were maximum at 3.61 % jute fiber content. This study demonstrated that the addition of jute fiber to perlite/gypsum composites results in improved mechanical properties up to a certain percentage of jute fiber, beyond which the properties deteriorate.

Effects of the addition of short straight steel fibers on the strength and strains of high-strength concrete during compression

The article presents the effect of the addition of short straight steel fibers on the behavior of high-strength concrete (HSC) under compression (σ–ε curves). Deformations of cylindrical samples were measured simultaneously with the use of linear variable differential transformers (LVDT), strain gauges and the method of digital image correlation (DIC). The study showed that as the content of short straight steel fibers increases, both the composite compressive strength (fc) and strains (ε0), which correspond to the stress equal to the compressive strength, increase as well. To a lesser extent, the effect of short straight fibers on the descending part of the σ–ε curve was observed. An increase in the density and toughness ratio of the compressive strength of high-strength concrete with fibers compared to concrete without fibers was also observed. Moreover, compressive strength of the composite was estimated using the ultrasonic method. Based on the obtained results, a statistical analysis and an estimation of parameters fc and ε0 were carried out, and an analytical model was proposed to describe σ–ε relationship for HSC reinforced with short straight fibers under compressive loading. The results obtained for compressed fiber-reinforced concrete were compared with data available in literature.

Study on Coordinated Deformation Failure Mechanism and Strength Prediction Model of Rock-lining Concrete

Shotcrete has been widely used in the excavation of caverns and tunnels as a key load-bearing element in the support system. However, the interfacial stresses and bond strengths within the composite structures formed by the interaction of geologic bodies and tectonic formations are not well understood, which can lead to safety accidents and excessive wastage of support materials in engineering. To address this gap, rock-concrete composite specimens were created using six distinct types of surrounding rocks. The strength law of composite specimens was analyzed, and the uniaxial compressive strength prediction model of composite specimens was derived based on Mohr−Coulomb strength yield criterion. The results show that the uniaxial compressive strength of the composite specimen changes with the change of rock type, which is between the strength of rock and concrete. The uniaxial peak strength and elastic modulus of composite specimens are linearly positively correlated with the ratio (Y) of concrete-rock elastic modulus, which is easily affected by concrete properties. However, the peak strain is linearly and negatively correlated with Y, which is greatly influenced by rock. The rock-concrete interface of the composite specimen plays an important role in the failure of the specimen, which changes the stress transfer state of the composite specimen, produces uncoordinated deformation, and finally causes the failure of the specimen. The theoretical and test value error of the derived composite specimen uniaxial compressive strength prediction model are –1.19%~12.20%, and the theoretical calculation model can be used to predict the uniaxial compressive strength of rock-concrete composite specimens.

In-situ preparation of porous metal-ceramic composite from secondary aluminum dross and red mud for adsorption of organic pollutant

Secondary aluminum dross (SAD) and red mud (RM) are solid waste discharged from aluminum industry. SAD contains 10–25 wt% aluminum nitride (AlN) and RM contains 20–50 wt% iron oxide. In this work, porous metal-ceramic composite was in-situ made from SAD and RM. Iron oxide was reduced into Fe2Si by AlN, and the generated nitrogen created pores. It was studied that effect of raw material and thermal treatment on pore structure and properties of the composite. Porosity, bulk density and compressive strength of composite were 65.78%, 1.03 g/cm3 and 17.77 MPa, when SAD content was 40 wt% and sintering temperature was 1450 °C. About 95.9% of malachite green in waste water was adsorbed by composite after 24 h. The composite could be recycled by magnetic separation after adsorption, attributed to the magnetic Fe2Si. This work proposed a novel idea of making recyclable porous material for adsorption of organics in waste water.

Investigation of the microstructure and mechanical properties of an Al/SiC/ZrO2 hybrid composite by spark plasma sintering technique

The quantum of work with silicon carbide (SiC) and zirconium dioxide (ZrO2) in the aluminum hybrid composite material has increased due to the growing demand for lightweight materials for various industrial applications. The aluminum hybrid composite with the wt% of primary reinforcement particles of SiC was kept constant at 5%, and the secondary reinforcement particles of ZrO2 were taken by 5%, 10%, and 15%. The sintering parameters were used as the temperature at 600°C, holding time of 35 minutes, and pressure at 30MPa. In this work, the aluminum composite material reinforced with 5%wt of SiC particles compared the test results with aluminum hybrid composite reinforcement of SiC and ZrO2 nanoparticles. Adding ZrO2 reinforcements enhances the aluminum hybrid composite material's better microstructure, microhardness, tensile strength, compression, and yield strength.

Experimental Investigations on the Development of Hybrid Metal Matrix Composite of Al7075 on Microstructural, Mechanical, and Dry Sliding Aspects

Abstract This research work aims to synthesize a hybrid Al7075 metal matrix composite reinforced with sustainable and synthetic reinforcement. With the employment of an ultrasonic transducer, two-stage stir casting is used to synthesize composite materials. The prepared samples were machined and polished for mechanical, tribological, and microstructural characterization. Optical microscopy and field emission scanning electron microscopy with elemental mapping were used to analyze the microstructure of the composite material. The microstructural examination revealed the homogeneous dispersion of reinforcement particles throughout the matrix. With the incorporation of reinforcement, the synthesized composite's compressive strength and micro-hardness were both increased, and the highest values were found to be 569.172 MPa and 178.86 HV, respectively, in one of the samples (B3 sample) as compared to as-cast Al7075 alloy. Tribological examination of composite samples shows that wear-rate enhances with an increase in the content of reinforcement. The wear resistance of sample B3 is highest among all prepared composite samples. Wear debris, grooves, micro-cracks, and small pits were observed on the worn-out surfaces of the samples by field emission scanning electron microscope analysis.

AN INVESTIGATION ON THE MECHANICAL AND TRIBOLOGICAL PROPERTIES OF AN ULTRASONIC-ASSISTED STIR CASTING AL-CU-MG MATRIX-BASED COMPOSITE REINFORCED WITH AGRO WASTE ASH PARTICLES

This research work reports the influence of 3-μm-sized Palm Sprout Shell Ash (PSSA) reinforcement on the mechanical and tribological behavior of the Al-Cu-Mg alloy. Composites of varying weight percentages of reinforcement ranging from 1 to 6 at intervals of 1 Wt.% were produced using the ultrasonic-assisted bottom-poured stir casting technique. Microstructural studies, mechanical testing, and wear properties analysis were performed on the alloy and the synthesized composites. The microstructure of the obtained samples was examined using Scanning Electron Microscope, Energy Dispersive Spectroscopy (SEM/EDS), and X- Ray Diffraction (XRD). The XRD patterns provided confirmation of the presence of PSSA (SiO2 and Al2O3) particles. The addition of PSSA reinforcement has significantly improved the hardness, tensile strength, and compression strength of composites. The hardness, ultimate tensile strength, and compression strength were improved by 13.89%, 24.04%, and 32.93%, respectively, with the 6 Wt.% PSSA-reinforced composite. However, the incorporation of reinforcement has resulted in a decrease in the ductility of the Al-Cu-Mg alloy composite; the maximum decrement of 42.87% was with the 6% PSSA-reinforced composite. Tests were conducted at different loads and speeds to evaluate the wear behavior of the prepared samples. Superior wear resistance was observed in the composites. The fracture and wear mechanisms of reinforced and unreinforced were observed using SEM.

Synthesis of a356 alloy-variable particle sized boron carbide composites: investigations on mechanical behaviour and tensile fractography

Lightweight metal matrix composites made of aluminium are now essential in several fields, including aerospace and automotive. An important factor determining the quality and properties of the composite material is the ease or difficulty of evenly dispersing the reinforcement throughout the matrix. The goal of this research is to find out the impact of 40 and 90 µm varying- sized boron carbide (B4C) particles in A356 alloy composites. Using the liquid stir casting technique and K2TiF6 as the wetting flux, A356 alloy with 9 wt.% of B4C composites were prepared. SEM and EDS images were used to study the material’s microstructure. ASTM-approved methods were used to measure the material’s mechanical properties. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed that B4C particles were evenly distributed throughout the A356 alloy. The addition of B4C reinforcement to the A356 alloy matrix increased the hardness, ultimate, yield, compression, and impact strength of composites with a reinforcement size of 40 μm. The hardness of A356 alloy was enhanced by 40.7% and 34.6%, respectively, when 9 wt. % of 40 and 90 μm B4C were added. Similarly, there was a 34% increase in ultimate strength and a 31% improvement in yield strength. Both cases showed a little decrease in the ductility of the composites. Scanning electron micrographs were used to examine the morphologies of tensile fractured surfaces.

Evaluation and optimization of mechanical properties of laterized concrete containing fly ash and steel fiber using Taguchi robust design method

The present study employs the S/N ratio and multiple regression analysis to evaluate the mechanical properties of laterized concrete with fly ash and steel fiber. The study considers compressive, split tensile, and flexural strengths as responses at 7 and 28 days. The Taguchi L16 (4 *4) orthogonal array experimental design is applied to optimize the performance of mechanical properties of concrete by using the design of experiments. The replacement of 25% of the granite aggregate with laterite aggregate resulted in a 12.44% increase in the strength of M30-grade concrete after 28 days. The composite's compressive strength decreases when the replacement level exceeds 25%. The split tensile and flexural strengths of the composite showed an increase of 14.54% and 16.93%, respectively, compared to the control mix. Furthermore, the test outcomes for durability factors like drying shrinkage and rapid chloride penetration in steel fiber reinforced fly ash-based lateritic concrete mixes with a 50% replacement rate adhere to the prescribed standards, verifying their designed performance over the designated structural lifespan. However, after multiple regression analysis, it is found that the error related to the correlation between experimental and analytical value strength is about 5%. Microstructural studies of the ideal mix were performed at 28 days to further understand the morphology of the laterized concrete containing fly ash and steel fiber.

Robust anti-impact, energy absorption and thermal properties of polyurethane nanocomposites modified by phenol-amine chemistry

It is still a considerable challenge for polyurethane elastomers (PUE) to possess outstanding mechanical and thermal performance simultaneously against harsh dynamic impact environment due to their heat accumulation, thermal stress softening and mechanical failure. Thus, this article innovatively prepared binary nanofibers composed of carbon nanofiber (CNFs) and aramid nanofibers (ANFs) to reinforce PUE, where catechol (CC) and polyethyleneimine (PEI) were served as interfacial modifier between nanofibers and polymer matrix. PUE with 1.5 wt% binary nanofibers achieve 31.62 % increase in crosslinking density, 146.8 °C improvement in thermal decomposition temperature compared to Neat PUE. Besides, the absorption energy and dynamic compression strength of composites were increased by 40.36 % and 38.26 %, respectively. Because reinforced nanofibers with crosslinking network structures improve the interface interaction between fillers and matrix, facilitate stress transfer and increase the energy threshold of thermal decomposition. The paper supplements the impact resistance analysis of PUE-based protective materials under impact loads, providing a systematic and scientific reference for the design and manufacture of impact resistant materials.

Influence of Heat Treatment on the Mechanical Properties and Precipitation Kinetic of Sugar Palm Fiber Ash Reinforced LM26 Al Matrix Composites

Heat treatment is a commonly known treatment subjected to aluminum alloy and their composites to improve their mechanical properties for automotive, aerospace, and marine applications. The heat treatment was carried out to determine the influence of aging time and temperature on the mechanical properties of LM26 Al alloy reinforced with 0, 2, 4, 6, 8, and 10 wt% sugar palm fiber ash (SPFA) and its precipitation kinetics. The LM26 Al/SPFA composites were fabricated through the stir casting technique, solutionized at 500oC for 2 h, and quenched in water at room temperature. The quenched composites were aged at various ageing times and temperatures and allowed to air cool. The hardness, impact energy, tensile, and compression strengths of the aged composites were appraised. In addition, the precipitation kinetics were studied to validate the precipitation temperatures of LM26 Al matrix composites. The hardness of the composites increased with aging time and temperature, with LM26 Al/10 wt% SPFA composite reaching a hardness peak of 102.10 VH at an aging temperature of 180oC after 5 h, compared to 56.70 VH for LM26 Al alloy. Similarly, after 5 h of aging at 180oC, the LM26 Al/8 wt% SPFA composite achieved maximum tensile and compression strengths of 198.21 MPa and 326.22 MPa, respectively. Precipitation temperature decreased from 584.8oC (LM26 Al alloy) to 480.46oC (LM26/ 10wt% SPFA), indicating that adding SPFA improved precipitation kinetics. The age-hardened composite with high hardness, tensile strength, and compression strength makes it a promising piston material application in the automotive industry.

Impact Energy Absorption of Sisal Fiber Reinforced Ferrocement Slab Elements and Its Statistical Relationship with Composite Compressive Strength

This study evaluates the level of energy absorption of sisal fiber reinforced ferrocement (SFRFC) slab elements of size 300 mm × 300 mm × 25 mm) (thickness) through low-velocity impact tests. The slabs are reinforced with 2 and 3 layers of steel weld mesh as primary reinforcement; and the sisal fibers of short and long fiber length, S-FL = 20 mm and L-FL = 40 mm (respectively) of varying volume fraction, (FVf of = 0.25–1.00%) act as secondary reinforcement. The compressive, split-tensile strength and flexural strength of hardened sisal fibrous mortar and plain (control) mortar specimens are determined and presented. The initial impact energy absorption (IIEA) and ultimate impact energy absorption (UIEA) of SFRFC slabs were found to be higher than ferrocement (FC-control) slabs (reinforced with 2 and 3 layers of steel mesh) demonstrating the effective contribution of sisal fibers in improving the performance of ferrocement slabs. When the length of the sisal fibers was increased from 20 mm to 40 mm in SFRFC slab elements (in hybrid combinations of steel mesh of 2–3 layers and fiber volume fraction of 0.25–1%), the impact resistance has increased several-fold over FC-control slabs. The composite compressive strength (CCS) of SFRFC has substantially increased when sisal fibers (of short and long fibers) of fiber volume fraction (FVf = 0.25–1%) are added to FC-control slab elements. Statistical prediction models have been developed separately for three dependent variables, IIEA, UIEA and CCS keeping constant the four independent variables, mesh layers (ML), fiber volume fraction (FVf), fiber length (FL) and mortar compressive strength (MCS), and the predicted values matched with the experimental results, within the acceptable error range. This study has statistically established a significant relationship between UIEA and CCS of sisal fiber reinforced ferrocement (SFRFC) slab elements.

Polipropilen Lif Türü, İçeriği ve Uzunluğunun Sert Poliüretan Kompozitlerin Mekanik Performansına Etkisi

The purpose of this work is to improve mechanical properties of rigid polyurethane (RPU) composites used in traditional ceramic casting industry. Therefore, monofilament (mono) and fibermesh (fibril) polypropylene (PP) fibers with various lengths (3, 6, 12 and 18 mm) were incorporated to polymer matrix at different rates (0.5, 1.0, 1.5 and 2% by weight). Effects of fiber type and content on flexural strength, bending strength and compressive strength of composites were investigated. Surface morphology and thermal characteristics of composites were evaluated by SEM and TGA analysis, respectively. Bulk densities of specimens with and without PP fibers vary between 72,15-146 kg/m3. Compared to pure rigid polyurethane foam, bulk density of monofilament PP reinforced composites significantly increased and the highest density value (146,86 kg/m3) was reached in M6/2.0 sample. On the other hand, incorporation of fibrilmesh caused a decrease in bulk density. While the increase in percentage of mono PP increased flexural strength, the presence of fibril PP had a negative effect on strength. Compressive strength of all mono PP reinforced composites is higher than that of pure RPU, except for M6/0.5 sample. Besides, SEM analysis revealed that the presence of PP fibers generally reduced number of closed cells in composite structure. Experimental findings indicate that fiber type, content and length affect mechanical performance of RPU composites. In addition, it is possible to use mono PP fiber reinforced RPU composites as support apparatus in ceramic casting industry.