Decrease In Impact Resistance Research Articles

Evaluation of mechanical and wear properties of LM24/fly ash/titanium diboride hybrid metal matrix composites using stir casting

This study focuses on the development of novel hybrid composites based on the LM24 alloy, utilizing liquid metallurgy stir casting to incorporate dual reinforcements (titanium diboride (TiB2) and fly ash (FA)). The weight percentage of TiB2 was maintained at levels of 2.5%, 5%, and 7.5%, keeping the FA at 2.5% during the course of fabrication. The introduction of 7.5 wt% TiB2 and 2.5 wt% FA displayed a very notable 43.18% increase in hardness and a 21.53% increase in tensile strength of the hybrid composite compared to the LM24 alloy. Furthermore, hybrid composites with a total reinforcement of 10 wt% exhibited superior wear resistance across the entire range of applied loads. Tensile fractography revealed ductile fracture mode for the LM24 alloy, while hybrid composites displayed a mixed-mode fracture. High-load-induced abrasive wear with little plastic deformation was seen on worn surfaces of hybrid composites, whereas adhesive wear was the dominant type of wear in the LM24 alloy. The results show that hybrid composites have better mechanical and tribological properties because the reinforcement particles are well distributed and the load is transmitted optimally. However, it is noted that increased reinforcement levels lead to a reduction in ductility, resulting in decreased impact resistance for the hybrid composites.

Impact of Packaging Materials and Storage Duration on the Physical Properties of Mantangan (Merremia peltata)-Based Complete Wafers

This study evaluated how packaging materials (PM) and storage duration (SD) influence the physical properties of mantangan-based complete wafers (MbCW). The MbCW formulation consisted of 44% Merremia peltata, 16% Brachiaria mutica, and 40% concentrate. Ingredients were ground (2 mm), homogenized, steamed, and pressed to produce wafers. A 4 × 3 factorial completely randomized design assessed four PM types (WP: no packaging, PL: plastic, CB: cardboard, PS: plastic sack) and three SD levels (30, 60, and 90 days). Statistical analyses revealed significant PM × SD interactions (p < 0.01) for moisture content, impact resistance, and water absorption. SD alone affected density, specific gravity, shrinkage, and fungal concentration. Moisture content and water absorption increased over time, while plastic packaging uniquely improved impact resistance with extended storage. Other packaging types showed decreased impact resistance. Plastic packaging demonstrated superior performance, preventing fungal growth for up to 90 days, with only 1.06% mould at this time, compared to 4.43% without packaging. The effective shelf lives were 57, 54, 53, and 43 days for PL, CB, PS, and WP, respectively. In conclusion, plastic was the optimal packaging material for MbCW storage.

Selection of Additive Elements Focusing on Impact Resistance in Practical TiAl Cast Alloys

Despite the widespread use of TiAl alloys in many fields, their poor impact resistance has recently emerged again as a major issue. Therefore, in this study, the practical effects of additive elements were examined by considering impact resistance as the most important property of practical TiAl cast alloys. The impact resistance was evaluated via the Charpy impact test, which has been rarely applied to TiAl alloys, revealing that only V, Cr, Mn, and B slightly improved the impact resistance, compared to that of the Ti–Al binary alloy, both in the as-cast and heat-treated states. In contrast, Nb, Mo, W, Fe, Ni, Si, C, and N decreased the impact resistance. If a slight decrease in impact resistance is permitted, then only Si and C can improve the creep strength, and Nb and W can improve the anti-oxidation resistance. These results confirm the excellence of practical TiAl cast alloys developed a considerable time ago, containing these elements in addition to Cr, Mn, and B.

NUMERICAL INVESTIGATION OF AS-BUILT AND CARBON FIBER REINFORCED POLYMER RETROFITTED REINFORCED CONCRETE BEAM WITH WEB OPENINGS UNDER IMPACT LOADING

It is not uncommon to provide openings in beams due to utility needs such as mechanical, electrical and sewerage passages. However, no clear guidelines are available in code of practice to handle beam web openings and presence of openings in beams changes behavior of Reinforced Concrete beam into a more complicated one. This research work investigates response of RC beam with openings under impact loading and proposes application of carbon fiber reinforced polymer (CFRP) composites to restore lost beam performance due to the presence of web openings. 3D nonlinear finite element software LS-DYNA is used for model development, validation and parametric finite element analysis work. The accuracy of the nonlinear finite element models are verified using experimental results from literature. Further parametric studies are performed to optimize beam web openings on opening location, size and CFRP no. of layers and fiber orientation. Numerical results showed as compared to control, large opening cutouts in RC beam decreased impact resistance of a beam by 54%. Also, RC beam exhibited poor impact loading resistance close to loading point (mid span) and performed good near shear zone. As compared to control as-built RC beam, Carbon Fiber Reinforced Polymer (CFRP) composites strengthening reduced mid span deflection by 74% and improved beams brittle failure mode. Also, 900 fiber orientation complete wrapping resulted in reduction of shear cracking around opening however exhibited low overall impact resistance as compared with 0º fiber orientation.

An experimental evaluation on the dynamic response of water aged composite/aluminium adhesive joints: Influence of electrospun nanofibers interleaving

The impact response of adhesives is a critical design parameter considering their lifetime. Additionally, environmental effects such as water or moisture may cause to degrade of the polymer-based adhesive and shorten its service life. This study aimed to investigate the impact response of water-aged aluminium-composite adhesively bonded single lap joints (SLJs). Nylon 6.6 nanofibers modified with graphene nanoplatelets (GNPs) were introduced in the adhesion areas to increase adhesive performance. The water aging resulted in decreased impact resistance in all cases. However, nanofiber-modified SLJs exhibited comparatively higher impact performance under both non-aged and water-aged conditions. Further, the GNP reinforced nylon 6.6 nanofibers increased the maximum impact load by 15 and 19% compared to neat nanofibers before and after aging, respectively. The fracture surfaces were examined via scanning electron microscopy (SEM) to understand damage and toughness mechanisms. A schematic model has been developed to explain the mechanisms leading to improved bonding performance by applying N6.6 nanofiber reinforcement to the adhesion zone.

Mechanical characterization of heat treated Al2219 hybrid composites

Aluminium alloy matrix composites with Al2O3 reinforcements exhibit superior mechanical properties and utilize in several demanding fields’ viz., automobile, aerospace, defense, sports equipment, electronics and bio-medical. The present work emphasizes on improvement of microstructure and mechanical properties of age hardened graphite and alumina reinforced Al alloy matrix hybrid composites. Different composites with a constant carbon content of 1 weight % and 0, 2, 4 and 6 weight % Al2O3 as reinforcements are fabricated by using stir casting technic and tested for hardness, tensile and impact strength. Scanning electron microscopy (SEM) is performed to analyse the failure mode under tensile load. All the composites are subjected to age hardening treatment with solutionising temperature of 530oC and aging temperatures of 100 and 200oC. The peak hardness of the composites at two aging temperatures are noted. Tensile and impact tests are conducted for the peak aged specimens. Results show substantial increase in the hardness of the age hardened specimens in the range of 34-44% in comparison with the as cast specimens. Result analysis shows increase in tensile strength (upto 40%) and decrease in impact resistance (upto 33%) with the increase in weight % of reinforcements. As the aging temperature increases a reduction in tensile strength and impact resistance is observed in each composites.

Investigations on the influence of matrix and textile on the response of textile reinforced concrete slabs under impact loading

Textile Reinforced Concrete (TRC) is gaining its popularity as a construction material. It is essential to investigate new materials to quantify its expected structural performance and integrity. The purposed study is to investigate the influence of material type and volume fraction of textile and type of matrix on the impact behaviour of textile reinforced concrete slabs. Both glass and basalt textiles were used in the investigations. Based on the investigations, it is concluded that the type of binder influences the impact resistance at first crack as well as the delamination possibility. Glass textile reinforced concrete slabs show more displacement and more residual capacity compared to basalt textile reinforced concrete slabs. With increased number of layers, the basalt textile reinforced concrete slabs exhibited decrease in impact resistance due to delamination. As energy level increases, glass textile reinforced slabs show increase in peak displacement whereas basalt textile reinforced concrete slabs show a decrease. The investigations reported will be useful for extending the knowledge of textile reinforced concrete for various impact resistant applications.

Characterization of Structure–Property Relationship of Incoloy 825 and SAF 2507 Dissimilar Welds

This study was carried out to investigate the evaluation of dissimilar welding between Incoloy 825 Ni-based alloy and SAF 2507 super duplex stainless steel. Welding was conducted by pulsed current (PC) and continuous current (CC) gas tungsten arc welding (GTAW) methods using ERNiCrMo-3 filler wire. The microstructure of weld zones and base metal/weld interfaces as well as mechanical properties of weldments were characterized. The results detailed the formation of Nb, and Mo-rich phases in the inter-dendritic regions of weld metals leading to a decrease in impact resistance of weld zones in comparison to parent metals. Presence of more secondary phases at the CCGTA weld metal resulted in higher hardness and lower toughness than that of the PCGTAW sample. During tensile tests, fracture occurred at the Incoloy 825 base metal, and both weldments also underwent ductile mode of fracture. The research addressed the microstructure–property relationship for dissimilar weld joints.

Wood‐based composites with thermoplastic polyurethane as matrix polymer

ABSTRACTThis research reports the influence of the mechanical properties of thermoplastic polyurethane (TPU) as a function of wood filler percentage. Wood flour was mixed with two different chemically based TPUs. Also, moisture content during compounding process as well as the origin of moisture (wood or TPU) were studied. All experimental designs and statistical analysis were done with the software Design Expert Version 10. Composite preparation took place in a multi‐stage process. The results showed that 70% wood filler can be incorporated in the composite manufacture. The properties of the composite were mainly influenced by the proportion of wood and TPU. Wood flour increased the density, hardness, water absorption, and tensile modulus with a decrease in impact resistance and abrasion resistance of the composite. Tensile strength exhibited a decrease up to ∼35% wood content, but an increase with further addition of wood. Moisture content had only a minor influence on the mechanical and water absorption properties despite the noted severe moisture sensitivity of TPU, which usually leads to decline in mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46344.

A comment on the impact resistance of organic offshore coatings at low temperatures

The Communication reconsiders impact testing results on organic offshore coatings published in Cold Regions Sci. Technol., 127 (2016), 109–114. A contact mechanical approach, based on ball indentation, is applied to the problem in order to discuss the decrease in impact resistance at low temperatures. The approach covers qualitative trends and orders of magnitudes for the temperature-dependent impact resistance of organic coatings.

Featuring High Impact Polystyrene Composites Strengthened with Green Coconut Fiber Developed for Automotive Industry Application

Studies focused on generating products able to reduce environmental impact have been put in place, and those aiming at finding polymeric composites strengthened with natural fibers stand out among them. A composite was strengthened with coconut fibers in the present study, since the generation of coconut residues has increased in Brazil due to coconut water industrialization. The aim of the present study is to process a high impact polystyrene (HIPS) composite strengthened with coconut fiber and to verify its possible application in the automotive industry. Strengthened samples were prepared using coconut fibers in the proportions 10, 20 and 30% fiber to develop such HIPS composite. Analyses were performed in order to set the density, Shore A hardness and impact resistance of the processed composites. It was found that the density and Shore A hardness results in the HIPS did not change due to the addition of coconut fibers. However, it was observed that the impact resistance was reduced because of it. It was noteworthy that the decreased impact resistance did not preclude the use of the HIPS/coconut fiber composite, since it showed that such material can be used in parts free from strong mechanical stress such as those inside the automobiles. The use of coir HIPS also aimed at reducing costs related to the polymer’s consumption and at reusing the waste (coconut husk) from coconut water industries.

Investigation of Impact Behavior of TIG Welded Inconel 718 at Aircraft Engine Operating Temperatures

In this work, Charpy notch pendulum impact test was performed on non-welded and TIG (Tungsten Inert Gas) welded Inconel 718 specimens at three different temperatures as 20°C, 500°C and 700°C. After the completion of tests, SEM (Scanning Electron Microscopy) inspection and EDX (Energy-Dispersive X-Ray Spectroscopy) analysis were performed for the microstructural examination of the specimens. Hardness measurements on the rupture zone of selected welded and non-welded specimens were also performed to make a better approach to interpretation of the impact behavior of material. Inspections indicated that hardness values in the heat affected zone of welded specimens dramatically decreased and they displayed higher ductility during fracture than non-welded samples due to partial softening of structure. The reason of further decrease in impact resistance of welded specimens was explained as the precipitation and coarsening of γ′′ and carbide phases in the interdendritic regions with increasing temperature.

Effect of Fiber Length on Direct Tensile and Impact Strength of Cmentitious Materials Containing Silica Fume

This study is aimed to evaluate the tensile strength and impact resistance of cementitious materials which comprise steel fibers and silica fume in the mixes. Material variables include water-binder ratio, dosage of silica fume, steel fiber length and dosage. A designed tensile strength was used to perform the direct tensile in this study. Test results indicate that the compressive strength, splitting tensile strength and direct tensile strength of specimens for fiber length of 60 mm are higher than that of 35 mm. The inclusion of fibers in specimens containing silica fume has higher compressive and tensile strength; and lower impact resistance than the specimens made with silica fume. Incorporation of steel fiber and silica fume in composites achieves significantly higher increase in compressive strength, splitting tensile strength, and direct tensile strength than only individual use of steel fiber or silica fume and decrease in impact resistance than only individual use of steel fiber. Finally, the proposed direct tensile testing method is suitable for determining the tensile strength of fiber reinforce cementitious materials and generating the tensile stress-strain curves easily.

Wear Analysis of PM Compacts with Bainitic Microstructures, Under Unlubricated Sliding Conditions

Ferrous and non-ferrous alloys can be processed by PM. Complex shapes and good surface finishes can be achieved, leading to promising applications, if mechanical properties are demonstrated to be high enough. At the same time, both bainitic and carbide free bainitic microstructures have proved to be excellent candidates for wear applications. Therefore, the aims of this project were steered towards analysing wear behaviour of PM compacts, in relation to their bainitic microstructures.Three materials were employed and two conditions were taken into account: materials before and after austempering. A reference material was considered, corresponding to Distaloy DC with Mo and Ni. Microstructure was analysed in all the cases by means of optical and scanning electron microscope and it was related to the behaviour observed. Pin on plate reciprocating sliding test without lubricant was utilised in order to measure friction coefficient and specific wear rate in the pins. Effects of alloying elements were also examined.It was found that austempering decreased impact resistance, but enhanced hardness in Distaloy DC. In contrast, the other two materials presented the opposite behaviour. However, the presence of additional alloying elements in the initial composition fulfilled to increase wear resistance, compared to the reference material. A possible interaction between pores and oxides that may influence wear behaviour was observed. Si allowed carbide free bainitic microstructure to form but heterogeneity could not be prevented. Therefore, the advantage of this microstructure could not be fully used. Results obtained in the present work can lead to new wear applications for PM products, containing bainitic microstructures.

Resistencia a los impactos: una mirada óptica

<p>El objetivo de este artículo de revisión de tema es aportar información acerca de un aspecto que pocas veces se tiene en cuenta (principalmente por la falta de material documentado, escrito o publicado) en el momento de realizar una prescripción a una persona que requiera una ayuda óptica. Se analizará, desde diferentes puntos de vista, el aporte de un lente oftálmico a la seguridad y salud del paciente, con independencia del material en que se fabrique. La resistencia a los impactos de un sistema óptico depende de muchos aspectos, entre ellos: el espesor del lente, el índice de refracción del material, la curva base utilizada para su fabricación y la aplicación o no de tratamientos ópticos como el antirrayas, el antirreflejo y los fotosensibles. Todos los análisis de este tema se realizan a estudios basados en las indicaciones dadas por instituciones como ANSI (Estados Unidos), OLA (Estados Unidos), CSA (Canadá) y AS/NZS (Australia), para aplicar pruebas que miden la resistencia de lentes como Drop Ball Test, además de pruebas balísticas de velocidad y alto impacto. Se puede concluir que el policarbonato es el material más resistente y que el espesor central tiene relación directa con la fortaleza del lente. Adicionalmente, entre más plana sea la curvatura base, mayor es la fragilidad del material, y el tratamiento antirreflejo influye de manera directa en la disminución de la resistencia a los impactos, a diferencia de los tratamientos fotosensibles, los cuales no alteran esta propiedad.</p><p> </p>

An investigation into the correlation between nano-impact resistance and erosion performance of EB-PVD thermal barrier coatings on thermal ageing

Nanomechanical testing (nano-impact and nanoindentation mapping) has been carried out on the top surfaces of as-received and aged 8wt.% yttria stabilised zirconia (YSZ) thermal barrier coatings (TBCs) produced by electron-beam physical vapour deposition (EB-PVD). The correlation between the nanomechanical test results and the previously reported erosion resistance of the TBCs has been investigated. The experimental results revealed that aged TBCs on zirconia for 24h at 1500°C or on alumina for 100h at 1100°C resulted in large increases in their hardness (H), modulus (E), H/E and H3/E2 ratios but their erosion resistance was reduced. Nano-impact tests showed a dramatic decrease in impact resistance following the ageing of these TBCs, which is consistent with the erosion results. The strong correlation between the nano-impact and erosion resistances has confirmed the premise that rapid laboratory impact tests must produce deformation with similar contact footprint to that produced in the erosion tests.

Effect of temperature and pressure of hot pressing on the mechanical properties of PP–HA bio-composites

This paper focuses on the effects of pressure and temperature in hot press molding on the mechanical properties of polypropylene–hydroxyapatite composites with two different types of silanated and unsilanated hydroxyapatites. Density, crystallinity, ultimate tensile strength, Young’s modulus, and impact resistance were evaluated for the two types of composites. Increasing pressure caused enhancement of density, crystallinity, MFI, ultimate tensile strength, and Young’s modulus. Increases in temperature increased MFI, ultimate tensile strength, and Young’s modulus whilst decreased impact resistance of composites. Effects of increasing pressure and temperature on the mechanical properties of polypropylene–silanated hydroxyapatite were less than their effects on the mechanical properties of polypropylene–unsilanated hydroxyapatite. Micrographs showed changes in fracture mode from ductile to brittle with increasing pressure and temperature during hot press molding.

Effects on Impact and Tensile Behavior of Transparent Polymer Materials by the Addition of Anti-Biofouling Agents

This paper reports the effects on both the impact and tensile behavior, impact resistance, modulus, strain at break, and peak load for a series of polymers with anti-biofouling agents added. The materials include PMMA, bisphenol-A polycarbonate, and a co-polyterephthalate derived from 2,2,4,4-tetramethyl-1,3-cyclobutanediol and 1,3-propanediol (CBDO). The anti-biofouling agents studied were the algaecides Irgarol 1051 and Diuron. The anti-biofouling agents were not simply used as a coating but were compounded into pelletized material and then compression molded into test plaques. The results show that PMMA is the only polymeric material studied that does not show a decrease in impact resistance with an increasing quantity of the anti-biofouling agent. With respect to modulus, strain at break, and peak load, both PMMA and CBDO showed little dependence on the amount or type of anti-biofouling additive.

Novel inorganic/organic hybrid materials based on blown soybean oil with sol–gel precursors

New ceramer coatings based on blown soybean oil with sol–gel precursors were prepared and evaluated as a function of the blowing process and sol–gel precursors content. Soybean oils were blown at three different rates in order to optimize the blowing process. Three sol–gel precursors, titanium (IV) i-propoxide, titanium (IV) di- i-propoxide bis-acetoacetonate, and zirconium n-propoxide were then used with the blown oil to investigate the effect of sol–gel precursors content on film properties. The gelation and film properties of ceramer coatings were dependent on chemical composition, which was a function of blowing time and blowing rate. Both tensile properties and general coatings properties (including adhesion, hardness, impact resistance, and flexibility) were investigated as a function of sol–gel precursor content. In general, higher sol–gel precursor content increased tensile strength and modulus, but decreased impact resistance.

INSTRUMENTED IMPACT BEHAVIOR OF PARTICULATE-FILLED COMPOSITES

A study of the influence of calcium carbonate on impact energy of CaCO3/high-density polyethylene composites was conducted. Composites with calcium carbonate in the range of 0–40% were produced by twin-screw extrusion followed by compression molding. Notched Izod impact tests of composites were carried out using an instrumented impact tester. It was found that increasing the calcium carbonate content decreased impact resistance. Transition in total impact energy with filler content was observed at 20% filler volume fraction, similar to propagation energy. In the case of the initiation energy, the transition was found at a different level, 10% filler volume fraction. The impact fracture process of polyethylene was seen to be initiated by crazing, followed by brittle failure, whereas composites were initiated by microvoid nucleation from interfacial failure between the filler and matrix and were propagated via microvoid coalescence.