Point Flexural Test Research Articles

Development of hybrid green composites by dual natural fibers (jute/bamboo) reinforcement and investigation of their mechanical behavior

AbstractThis study aims to investigate the mechanical properties of natural fiber hybrid composites, specifically those based on jute and bamboo fibers. Jute fibers made in the form of highly scattered mesh and fine‐meshed bamboo mat were selected as reinforcing materials. The highly scattered meshed jute fabric composite showed poor mechanical properties owing to resin agglomeration, leading to the brittle fracture of the composite before elongation. In contrast, the randomly oriented fine‐meshed bamboo fabric performed better in terms of both mechanical properties and strain energy absorption under the same loading conditions. Hybridization with fine bamboo mesh fibers can be a solution to improve the mechanical properties of jute fabric composites. The tensile, flexural, and in‐plane shear properties of the composites are investigated in our study. We found that hybridizing a fine‐meshed bamboo mat with jute fabric resulted in an improved mechanical performance of the composite. Composite panels have been manufactured using vacuum assisted resin transfer molding (VARTM). Experimental and numerical methods have been used to investigate the flexural behavior. Of the stacking sequences considered, the (J/B4/J) stacking showed the highest flexural strength (141.1 Mpa) and the (B2/J2/B2) 2/2 stacking sequence showed the minimum flexural strength. The alternating stacking sequence (B/J/B/J/B/J) exhibited intermediate properties. The randomly oriented bamboo fabric near the neutral axis enhanced the properties of the hybridized composite. This was verified numerically using the ANSYS ACP software.Highlights Mechanical behavior of Hybrid composite of two natural fibers was investigated. Vacuum assisted resin transfer molding was used to manufacture composite panels. Tensile, in plane shear, 3 point flexural tests and SEM micro analysis were done. FEA was used to validate and compare the experimental and numerical results. Resin agglomeration was improved by fibers with better resin impregnation property.

Structural Behaviour of Kenaf Fibre Lightweight Concrete Beams Modelling Via FEM-Abaqus

This study presents the structural properties of oil palm shell kenaf fibre Lightweight concrete (OPS-KFLC) beams. The main objective of this research was to investigate the potential advantage of kenaf fiber for improving the structure properties of OPS-RC beams. This investigation carried out by two methods experimental and consequently numerical modelling. The experimental work focused on two beams. First beam constructed with full shear reinforcement and without fibre (SI = 0% and with Vf = 0%) denoted as a control beam. Meanwhile one more beams with full shear reinforcement (SI = 0%) and with fibre volume fraction of Vf = 1% constructed respectively. The experimental work has been considered four point flexural tests on simply supported beam. Consequently, numerical modelling with finite element method FEM software Abaqus for calibration and validation of experiment results considered. First, sensitivity analysis (mesh and time) conducted up to acquire the best correlation with experimental result. Then, the experiments result of beams was used, for calibration in FEM modelling investigation. The results comparison showed that there is a good agreement between the experimental test and nonlinear finite element analysis NLFEA results. Generally, this investigation demonstrated up to 37% improvement on structure properties of OPS-RC beam by addition of Vf = 2%kenaf fiber.

Spray binder for automated preforming: Spray process and preform properties

AbstractA closer look was taken at a spray binder and the properties of the preforms made with said binder and non‐crimp carbon fiber textiles. First the spray process was analyzed, then T‐peel and three point flexural tests were carried out to compare the spray binder to other binder systems. While the spray binder showed higher peel strength than most binders found in literature, the measured flexural strength was lower than the values found for powder.

Vol4 num2-20 Manufacturing and testing of a new CFRP node bonded by adhesives for its use in bus structures

In recent years exponential increase in the use of adhesives in industrial processes is observed. Nowadays these materials are used in applications as diverse as aerospace industry, automotive industry, railway industry or even civil construction. In the same way, the use of composite materials has grown enormously, especially in the aerospace industry, thanks to the benefits that this type of materials are able to provide, even as reinforcement. Current bus structures present serious problems of fatigue due to their rigidity, resulting in unexpected failures in certain nodes where stresses are concentrated. This work is part of a project that it is trying to provide more elasticity to the structure through the use of a new CFRP node joined by adhesives to the bus structure using polyurethane. The complex design of the node has caused numerous manufacturing problems. PLA node was manufactured using 3D printing for being used as a core. PLA node was covered layer by layer with CFRP by hand lay-up. In order to know the behavior of the whole set (CFRP node, adhesive and steel beams), four prototypes were manufactured and tested. Four point flexural test was carried out on the prototypes to validate the assembly. Results show the suitability and capacity of this new node concept to be used in bus structures. In recent years exponential increase in the use of adhesives in industrial processes is observed. Nowadays these materials are used in applications as diverse as aerospace industry, automotive industry, railway industry or even civil construction. In the same way, the use of composite materials has grown enormously, especially in the aerospace industry, thanks to the benefits that this type of materials are able to provide, even as reinforcement. Current bus structures present serious problems of fatigue due to their rigidity, resulting in unexpected failures in certain nodes where stresses are concentrated. This work is part of a project that it is trying to provide more elasticity to the structure through the use of a new CFRP node joined by adhesives to the bus structure using polyurethane. The complex design of the node has caused numerous manufacturing problems. PLA node was manufactured using 3D printing for being used as a core. PLA node was covered layer by layer with CFRP by hand lay-up. In order to know the behavior of the whole set (CFRP node, adhesive and steel beams), four prototypes were manufactured and tested. Four point flexural test was carried out on the prototypes to validate the assembly. Results show the suitability and capacity of this new node concept to be used in bus structures.

Load deflection behaviour and properties of sustainable lightweight aggregate concrete slabs

This research has been conducted to investigate the effect of partial replacement of coarse aggregate by lightweight aggregate on different characteristics and load deflection behaviour of concrete. Natural aggregate was replaced once by waste walnut shell and then by porcelinate aggregate. And both types are considered lightweight aggregate. Percentages of replacement by volumetric rates ranging between 25% to 100% were adopted. In addition, cement was replaced by 10% waste glass powder. Compressive strength, splitting tensile strength, and dry density were made. Also, one-way slab was cast for 50% replacement and tested under four point flexural test. Results showed that replacement of natural aggregate with lightweight aggregate regardless of its source decrease density, compressive strength and splitting strength. While an increase in the deflection at failure was noticed for slabs incorporating lightweight aggregate compared to the reference one. Concrete containing 50% porcelinate demonstrated a slight increase in strength compared with the reference slab by 8.91% concrete containing 50% WA demonstrated a clear reduction in strength compared with the reference slab by 62.57%. The width of crack at failure for concrete incorporating walnut coarse aggregate was wider for the reference one. While concrete incorporating porcelinate failed with finer cracks than the reference one.

FEM Analysis of Bridges with Encased Continuous Shear Connectors

AbstractComposite steel‐concrete constructions with encased I‐beams were initially used as composite floors. Nowadays, they can be usually seen as short railway bridges with span up to 20m. Their main advantages include simplicity of their construction, their low construction height and their effectiveness. To make them more effective, the steel I‐beams were replaced with perforated steel strips. At Technical University of Košice, Faculty of Civil Engineering, several continuous shear connectors with new design were proposed. In order to prove their effectiveness, numerous experiments – push‐out tests, four point flexural tests – were performed at Laboratory of Excellent Research. The purpose was to determine the shear and bending resistance of the connectors. Afterwards, the finite element models were created and analyzed using ABAQUS/CAE software. This paper deals with numerical program of four‐point flexural tests of two strips. The most clue modules ‐ properties, load, step, interaction and mesh are described.

Flexural strength test on new profiled composite slab system

This research presents an experimental study on the flexural strength and failure behaviour of a newly developed composite metal decking system. The newly developed metal decking system with a thickness of 0.75 mm and 1.0 mm produced by the industry requires a detailed study in strength and performances before it is launched for commercialization. A simply supported conventional reinforced concrete slab is used as the control specimen and two composite slabs with different metal thickness of steel sheet profiles were constructed and tested under a four points flexural strength test. The strength and behaviour of the slabs are recorded and comparisons with conventional slabs with composite deck slabs are made to achieve the objectives. The recorded results of three different slabs were then used to plot a load-displacement graph and deflection profiles are to be analysed and compared. The yield flexural capacity and average yield displacement of specimens for the composite slabs were 28.0 kN and 0.80 mm respectively. The 1.0 mm metal thickness composite slab has the highest ultimate flexural capacity among all specimens which is 84 kN followed by a 0.75 mm metal thickness composite slab with 58 kN and ends with the lowest 9.1 kN of conventional slab. Two cracking patterns were found during the experimental test which includes shear cracking and flexural cracking`. Besides that, two major failure modes under bending which are flexure failure at the centre point of the specimen and bond or longitudinal slip failure along the side of the specimen were found in the experimental test. Bond failure results in slippage between the concrete and metal deck, which can result in cancellation of the composite action at interface. In conclusion, the strength of slabs improved, and ductility was remarkably increased when slabs acted as a composite structure.

Flexural Resistance Analysis on Hot Asphalt Mixtures with Wire Mesh Placement Modeling as Reinforcement

Flexural resistance is the ability of a specimen to withstand force in two pedestals with vertical axis until it is broken. Flexible pavement is a type of pavement which is very dependent with pavement course underneath. The dependency of flexible pavement in both base course and subgrade makes this pavement difficult to apply in unstable soil. Using wire mesh course as reinforcement is considerably able to raise the flexural resistance. This study is aimed to analyze flexural resistance value in hot mix by using wire mesh course as reinforcement. The study is conducted by applying experimental method with designing four types of wire mesh laying models in hot mix using three points flexural test equipment. Based on the study result, it is found that hot mix with wire mesh laying 30 mm from specimen surface is the best model type with 291,85 KN flexural resistance value with 8 mm of deflection depth. In this laying, it can be concluded that wire mesh course can raise up the flexural resistance up to 35,41% compared to the hot mix without wire mesh course.

A Comparative Experimental Investigation on Laced Reinforced Concrete Beam and Conventional Beam under Monotonic Loading

Laced Reinforced Concrete (LRC) structural elements are generally used in the defence environments where the structure encounters blast/impulsive loading. It comprises of equal number of reinforcements in both the faces of the beam with lacings as shear reinforcements bent at 450 along the plane of principal bending and fastened in position by cross rod. This paper presents the performance of LRC beam by experimental investigation and compared with conventional Reinforced Concrete (RC) beam using four point flexural load testing. Experimental results indicate that the LRC beam perform well than the RC beam considering the deformation. Failure modes could not be ascertained, since the experiments were stopped due to limitations in test set-up. At this stage, the support rotation achieved by LRC beam and RC beam is found to be 4.70 and 2.430 respectively. The LRC beam is found to be more ductile than RC beam. The structural response of LRC beam and RC beam is compared and presented.

An experimental study on the flexural behavior of cold-formed steel composite beams

Local buckling instability under compressive stresses is common in cold-formed steel (CFS) members and generally occurs well before the material has reached its yield strength. This results in under-utilization of the cross-section, compared to its full capacity governed by strength failure. Under flexural loading these CFS members possess sufficient inelastic reserve strength up to the ultimate stage. A recent study indicated that plate girders with tubular flanges offer higher flexural and torsional strengths compared to the ones with flat flanges. Upon packing of the tubular compression flange of CFS beams with hard materials like concrete/ timber etc., there will be a substantial delay in early local buckling instabilities, thus improving their load carrying capacity considerably. Although, numerous CFS composite sections have been developed recently, very limited lightweight packing materials have been adopted. The current study presents an experimental investigation carried out on CFS beams with flanges and webs possessing rectangular box geometry, packed with suitable low-cost lightweight packing materials, resulting in novel light-weight CFS composite beams. Four point flexural tests were conducted on these beams with simply supported end conditions. The ultimate strengths, modes of failure, load vs. displacement plots were obtained to study their flexural behavior, in order to evaluate the structural efficiency of the different packing materials. Lastly, the North American Specifications and Australian New Zealand Standard for CFS structures were also used for determining the design strengths of the specimens for comparison sake. This study proved that these novel CFS composite beams have shown better performance considerably.

A novel route for volume manufacturing of hollow braided composite beam structures

This work investigates the application of a rapid variothermal moulding process for direct processing of a braided thermoplastic commingled yarn. The process uses locally controllable, responsive tooling which provides opportunities for optimum part quality and significantly reduced cycle times compared with conventional processes. The proposed process was used to directly manufacture hollow beam structures from dry commingled braided preforms. It was demonstrated that the cycle time using the rapid process was reduced by more than 90% as compared to a conventional bladder moulding process, resulting in a total cycle time of 14 min. Additionally, initial three point flexure test results indicated an improvement in the mechanical performance of the resultant parts as compared to the benchmark.

Mechanical, thermal and interfacial properties of Carbon-Kevlar reinforced epoxy composite

Twill woven Carbon-Kevlar (CK) fabric was reinforced in epoxy matrix by conventional hand lay-up process. The fabric weight fraction in the composites was kept around 58% and stacking sequence was varied from single to five plies. Tensile test was performed and the fracture surface after tensile test was evaluated by scanning electron microscope (SEM). The test result revealed that the tensile properties are strongly dependent on the number of plies. Three point flexural test of the composite was also carried and an increasing trend was observed. Maximum impact energy was recorded for CK3 sample by 202.7 KJ/m2. Thermal stability of the composite was studied via the thermo gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) result show interaction between fiber and matrix material. Finally, CK fabric reinforced epoxy-based composites showed balanced and tailor-able mechanical properties by varying the number of plies, suitable for desired applications in many areas including building, construction, marine, automotive, etc.

Frozen Stresses in Shape Memory Polymer Composites

Shape Memory Polymer Composites (SMPCs) are a class of smart materials in which the structural properties of long-fiber polymer-matrix composites and the functional behavior of Shape Memory Polymers (SMP) are combined together. In this study, the frozen stresses resulting from fixing a deformed shape have been investigated. Two different samples were manufactured, with and without significant shape memory properties, and a three point flexural test equipment was used in order to fix a deformed shape. The forces and the resulting stresses were measured during the samples deformation and after the shape freezing. The experimental tests have shown that the shape memory sample has a better ability to fix a deformed shape, since its frozen stress is higher in all the tests.

Novel sprue designs in metal casting via 3D sand-printing

The opportunity to improve the quality of metal castings by enabling fabrication of complex gating systems via 3D Sand-Printing (3DSP) has been recently established. Among the different components of a gating system (often called rigging), sprue design offers a major opportunity to exploit the unlimited geometric freedom offered by 3DSP process. In this study, conventional principles of casting hydrodynamics is advanced by validated novel numerical models for novel sprue designs to improve melt flow control. Computational flow simulations demonstrate that conical-helix sprue satisfy the critical velocity condition by reducing the ingate velocity below 0.5 m/s. Multiple approaches to integrate 3DSP into conventional manufacturing to fabricate complex gating systems through “Hybrid Molding” are presented. 3DSP molds featuring two optimized sprue profiles and a benchmark straight sprue are fabricated to pour 17-4 stainless steel. Computed tomography scans (CT) shows that parabolic sprue casting (PSC) and conical-helix sprue casting (CHSC) reduced overall casting defects by 56% and 99.5% respectively when compared to straight sprue casting (SSC). Scanning electron microscopy (SEM) analysis confirms the presence of globular oxide inclusions and that PSC and CHSC exhibits 21% and 35% reduced inclusion when compared to the SSC. Three point flexural testing reveals that CHSC and PSC exhibits an increase of 8.4% and 4.1% respectively in average ultimate flexural strength than SSC. The findings from this study demonstrate that numerically optimized gating systems that can only be fabricated via 3DSP have the potential to significantly improve both mechanical and metallurgical performance of sand castings.

Automation of the mechanical tensile and three-point flexural test

This paper presents the design and implementation of Mechanical system testing for tensile and three-point flexural test for both metallic and polymeric materials. A control and monitoring system was adapted to the data, using specialized equipment for industrial automation, i.e. PLC system. Main Parameters to perform the tensile and three point flexural tests, and the functional and technical specifications according to the ASTM (American Society of Testing Materials) standards were defined. Conceptual design, mathematical calculations and CAD designs were developed using Solidworks. Graphical user interfaces (GUI) were designed to interact with the user. Human machine interface (HMI) was implemented in proprietary software and includes rules for the supervision and manipulation of core variables for the user according to the ASTM standard. The HMI was interconnected with a programmable logic controller (PLC) where the process selection rules was implemented in GRAFCET diagram, following the ASTM protocols. The system has a test capacity of 500 Kgf both for the tensile test and for the three-point flexural test, with an accuracy of ± 2%, under the ASTM E177 standard, and the HMI interface as an innovative monitoring and control system.

Process-property-performance relationships in CFRP composites using fractal dimension

The present study considers the dependence of the mechanical properties on the fibre architecture for composite laminates. Woven carbon/epoxy fabric composites were manufactured by the resin transfer moulding (RTM) process. Image analysis and fractal dimension (D) were used to quantify fibre distribution and resin-rich volumes (RRV) then correlate these data with the mechanical properties of the fibre-reinforced composites. The static strength of these composite laminates showed a clear dependence on the fibre distribution. Four- point flexural fatigue tests were conducted under load control, at a sinusoidal frequency of 10 Hz under load amplitude control with a stress ratio (R=σmin/σmax) of 0.1. Specimens were subjected to maximum fatigue stresses of 95% to 82.5% step 2.5% of the ultimate flexural strength (UFS). The fatigue properties of the composite laminates are shown to have statistically significant correlations with the fibre distribution and the static properties of the laminates. A loss of 5-6 % in the flexural modulus of the composite laminates predicted an increasing probability of failure of the composite laminates under fatigue loading. This occurs at about 90% of the fatigue life at a particular stress level.

Design of Composite Structures Using Advanced Numerical Tools

The main topic of the presented paper is review of the mostly used tools in designing of composite structures. Consequently, practical demonstration of their using has been done on an example of a bending test of the wound, thin-walled composite rod. Further methods of definitions individual layers and the associated interface properties using the cohesive elements, based on that it is possible to detect arising delamination. Unlike conventional approaches, there is not possible to define a definite strength limit or nonlinear plasticity. For this purpose, the so-called failure criteria exist for the composite materials. In this way, it is possible to describe the real stress/ strain situation for the composite parts. Composite materials, due to their anisotropy, offer by suitable layer composition the possibility of significantly improving the efficiency of material utilization. Just in such cases, some advanced numerical tools like e.g. DOE, response surface and genetic algorithms could be used. Based on the above described methods, the experimental results of the carried three point flexure test have been numerically verified and the properties of the tested rod optimized.

Performance Evaluation of Plant Produced Warm Mix Asphalt

Warm mix asphalt (WMA) is relatively a new technology which enables the production and compaction of asphalt concrete mixtures at temperatures 15-40 °C lower than that of traditional hot mix asphalt HMA. In the present work, six asphalt concrete mixtures were produced in the mix plant (1 ton each) in six different batches. Half of these mixes were WMA and the other half were HMA. Three types of fillers (limestone dust, Portland cement and hydrated lime) were used for each type of mix. Samples were then taken from these patches and transferred to lab for performance testing which includes: Marshall characteristics, moisture susceptibility (indirect tension test), resilient modulus, permanent deformation (axial repeated load test) and fatigue characteristics (third point flexural beam test). The obtained results indicated that the performance of WMA is enhanced when using the hydrated lime as filler in comparison with the limestone dust and Portland cement fillers. Better fatigue life was obtained for WMA using hydrated lime filler in comparison with HMA. Regardless the filler type, the Marshall properties of WMA satisfy the requirement of local specification, other properties of WMA were relatively lower than the HMA.

Shell Mould Strength of Rice Husk Ash (RHA) and Bentonite Clays in Investment Casting

Investment casting process (IC) plays a major role in the modern manufacturing process in providing an economical means of mass production components with intricate shape and complex geometry as demand in various crucial applications including aerospace, automotive, military, biomedical and others. This casting technique, develop shell mould fabrication by coating the required pattern with a refractory mixture which offers the complex geometrical shape and sizes parts to be cast. However, the modern IC approach in shell mould production suffers from zircon’s cost and supply instability as it is the main material to be used. Zircon uses as refractory filler for slurry production, and also in the form of sand used as stucco particles, is favoured by the investment casting facilities and industries as it exhibits the most versatile properties such as low thermal expansion and low reactivity to the metal to be cast. During the period of zircon supply shortage, many facilities introduce several alternatives. Currently, the step taken to reduce the cost of primary slurry material is by using some alternate refractory material like, alumina, silica, to be used with zircon for shell mould production. In relation to that, several researches continue to search for alternatives approach for shell mould materials. This research introduces the alternative method in fabricating investment casting shell mould as recognized from investment casting industry located in Sungai Puar of Bukittingi Padang Indonesia. This industry employs several local resources to fabricate the shell mould. These materials consist of rice husk ash (RHA), and two types of bentonite clays. The bentonite clays were obtained nearly from Kota Payakumbuh in the western provinces. However, this industry suffers from weak shell mould strength and need to be investigated and consulted. In this paper, the investigation on shell mould strength made from rice husk ash (RHA), and bentonite clays were conducted. The strength was measured by its modulus of rupture (MOR) performed in 3 points flexural bending test. The green and fired shell mould strength was determined from five type of slurry composition. The results revealed that the highest green and fired strength obtained were 0.157 MPa and 0.361 MPa from shell mould sample C of RHA (46%) and bentonite (54%) of its composition.

The Influence of Thermocycling on the Flexural Strength of a Polyamide Denture Base Material.

ObjectiveThe aim of the present study was to evaluate the influence of thermocycling on the flexural strength of a polyamide base denture material.Materials and methodsA polyamide denture base material (Valplast) was tested, whereas a PMMA material (Vertex) was used as a control. Thirty specimens of each material were fabricated for flexural strength testing according to ISO 1567. They were prepared and stored in water at 37°C for 48 hours. The specimens of each material were divided into three equal groups (n=10). Flexural strength testing was performed immediately after water storage and after thermocycling (5°C / 55°C, 2 c/min) for 3000 and 5000 cycles. A three point flexural test was performed on a universal testing machine at a crosshead speed of 5 mm/min. The final flexural strength was calculated using the formula: FS = 3 PL/2 bd2. A two-way ANOVA with post-hoc analysis using Tukey's procedure was applied at .05 level of statistical significance.ResultsA statistically significant reduction in flexural strength was recorded after thermocycling at 3000 cycles for PMMA and at 5000 cycles for both materials. The flexural strength of PMMA was significantly higher compared to polyamide for all the conditions tested (p<0.05).ConclusionThermocycling had a significant adverse effect on the flexural strength of polyamide and PMMA denture base materials.