Hot Moulding Research Articles

The effect of fibre content on properties of ceramifiable composites

ABSTRACTWith the development of rocket and aerospace technology in recent decades, people have put forward higher requirements on the heat resistance and ablation performance of thermal protection materials. In this paper, zirconia fibre hybrid alumina fibre/boron phenolic (ZA/BPF) ceramifiable composites, based on ceramic fillers of MgO, Al2O3, SiC and mica-modified boron phenolic resin matrix, were prepared with different hybrid fibre contents (5, 10, 15, 20, 25, 30 wt-%) by hot compression moulding. The result shows that fibre contents have little effect on the ablation resistance of composite materials which all have a low linear ablation rate below 0. 01 mm s−1. When the fiber content is 25%, the ZA/BPF composite reaches the highest bending strength 48. 86 MPa and 15. 57 MPa before and after sintering respectively. It is showed by the SEM results that too high and too low fibre content would both lead to poor bonding between resin and fibre interfaces.

Low velocity impact behavior of carbon fibre composite curved corrugated sandwich shells

Composite thin-walled curved structures are widely used in aerospace, marine, automotive and building engineering application. In this paper we design and fabricate a series of carbon fibre composite axial and circular corrugated sandwich cylindrical panels (ACSCPs and CCSCPs) by an in-house hot press moulding method. Low velocity impact tests are carried out to evaluate the impact resistance and failure mechanisms of such structures. Furthermore, validated finite element analysis (FEA) models based on the Hashin failure criteria are adopted to study the effects of the relative density, impact energy and impact position on their impact responses. It is observed that generally the peak forces and absorbed energies of the specimens ascend with the increase of the relative density. The impact responses, especially the ultimate loads of the present structures are particularly dependent on the impact position, but insensitive to the increase of the impact energy. By comparison, the ACSCPs generally have a more excellent impact resistance and energy absorption properties than that of CCSCPs. In addition, the corresponding energy contribution of the components for the ACSCPs and CCSCPs under different impact energy is also revealed, which could be useful for the multifunctional design of such kinds of composite curved sandwich structures.

The effect of heat treatment on microstructure and properties of laser-deposited TiC reinforced H13 steel matrix composites

With the development of laser technology, laser processing technology has become increasingly popular in the additive manufacturing, remanufacturing and repairing of hot work molds. Due to the special nature of laser processing technology, it is obviously different from the traditional forging or casting methods, resulting in the need for re-exploration and formulation of the heat treatment process. Therefore, this paper hopes to use laser deposition technology to add hard ceramic phase to prepare H13 steel composites, and to explore the effect of tempering treatment on the microstructure and properties of TiC reinforced H13 steel composites, and to provide theoretical support and practical reference for extending the life of H13 steel. The results indicated that the structure after laser deposition is mainly martensite and fine carbides. With the increase of the proportion of TiC, the structure of the sample becomes more fine and uniform. After tempering,the microstructure of the sample is high-temperature tempered martensite and fine carbides,and the distribution of TiC is more uniform.Compared with untempered amples, the hardness and tensile strength of the sample tempered are lower, but the wear resistance is enhanced.

Simulation of macrosegregation in direct-chill casting—A model based on meshless diffuse approximate method

A multiphysics numerical model has been developed for prediction of macrosegregation in direct-chill casting. The model uses volume averaged mass, momentum, energy, and species conservation equations to simulate the solidification of axisymmetric aluminium-alloy billets. The boundary conditions for the heat transfer include the effects of hot top, mould chill, and direct chill. The volume averaged conservation equations are solved with the explicit local meshless diffuse-approximate method. The approximation coefficients are evaluated on subdomains containing 14 nodes with the second order polynomial basis and the Gaussian weight function. Problems with instabilities due to strong convection are successfully eliminated with an adaptive shift of the weight function and evaluation position in the upstream direction. The automatic adaptive generation of computational node arrangement decreases the calculation time and in a straightforward way enables investigation of the complex flow for geometrically different inflow structures, including sharp and curved edges. The model is used for casting simulation of an Al-5.25wt%Cu alloy billet with a 120 mm radius for various inlet designs. The effect of inlet geometry on the temperature, solid fraction, melt flow, and macrosegregation is investigated. The described developments represent a first meshless numerical approach for simulation of macrosegregation of an important industrial process.

Biomimetic scaffold fabricated with a mammalian trabecular bone template

This study proposes the method of ultra-high molecular weight polyethylene (UHMWPE) biomimetic scaffold fabrication. Anisotropy is considered to be a distinctive feature of native bone but basically only a 3D-fabricated scaffold structure may be anisotropic, while 3D-printing is not applicable to UHMWPE. We proposed a novel method that suggested a template of native mammalian bone to be used as a negative for UHMWPE scaffold fabrication. This method allows direct replication of the bone's structural features on the micro- and macro-scale. Bone scaffolds obtained using the specified method showed anisotropic structure; the pores' average proportions for scaffold and bone were 770 and 470, and 700 and 500 μm, respectively. According to SEM and CT investigations, the scaffolds' macro- and microstructure mimicked the native bone architecture; this feature distinguishes the proposed method from the other UHMWPE scaffold fabrication techniques. The combination of the hydrophilic surface and the nanorelief affected the adhesion and proliferation of cells: the adhesion of multipotent mesenchymal stromal cells (MMSC) amounted to 40% after 4 h; the proliferation of MMSC was 75% after 48 h. The proposed novel method of fabricating biomimetic scaffolds can be used to obtain bone implants of the complex microstructure and anisotropy from high-melt viscosity polymers which cannot be 3D-printed to be further applied in bone reconstruction. The FT-IR analysis confirmed the occurrence of carboxyl oxidation when the surface of UHMWPE sample was treated with chromic acid. The oxidation index (OI) of the samples was found in the order of etching in chromic acid > sterilization > hot moulding respectively. It can be suggested that the oxidative degradation of UHMWPE can be reduced by optimizing manufacturing conditions and further selection of an appropriate processing method.

Development and Evaluation of Mechanical Properties of Biodegradable PLA/Flax Fiber Green Composite Laminates

Biodegradable or Green composites are gaining much interest as they are environmental friendly and have the potential to replace traditional composites. In the present work, a green-biocomposite was developed, processed and evaluated as an alternative to traditional composite automotive components, using PLA (Poly Lactic Acid, a biodegradable thermoplastic extracted from natural sources such as corn starch), as the matrix and Flax fiber as reinforcement. The flax fiber surface was modified before fabrication by Silane chemical treatment to improve adhesion and wetting. PLA/Flax composites were fabricated by manual hot plate compression moulding using indigenously developed test-rig. The mechanical properties of the Flax/PLA biocomposite have been tested for varying fiber weight percentages of 7.9%, 13.6% and 17.6%. The results of these tests indicate an increase in mechanical properties like ultimate tensile strength for the composite with increase in fiber content and for treated fiber / PLA composite, it reduces in contrast. The flexural strength for these three compositions remains same. However, the compression strength of the composite with 13.6 wt. % treated fiber increased as compared to 7.9% and 17.6% fiber reinforced composite.The absorbed impact energy of the PLA/flax fiber composite laminate is in the range of 25 to 30 Joules.The adhesion between PLA and Flax fiber is observed to be uniform throughout the cross-section area for all the three compositions.

Material selection in hot shaping molds of titanium alloys

Titanium alloys are widely employed in industries especially in aviation sector due to their high strength, light weight, superior corrosion resistance and other specific characteristics. Titanium alloys with superplastic properties are shaped by different methods. The present study aims at selecting the mold materials used for the shaping of titanium parts with a maximum thickness of 2 mm at 500-700 ° C. In the selection of mold material, the chemical composition of the alloy, process temperature, thermal fatigue cracks and the number of parts to be shaped are taken into consideration. In this study, distortion and surface oxidation are investigated for the molds used in the isothermal hot shaping of titanium parts in order to select the most suitable mold material.For this purpose, 7 different hot work tool steels and 3 stainless steel types, which are easily available in the market, have been selected. Due to the titanium shaping operations for 2-3 hours at 700 C°, samples were kept in the oven at 700 ° C for 30, 60, 120 minutes respectively, depending on the shape of the part. Furthermore, the oxide layer formed on the surface was observed separately for each cycle. The heating-cooling cycle was repeated 5 times for 120 minutes to determine the structural changes that may occur on the mold material surface. At the end of the process, the hardness and surface roughness of the mold materials were measured and corrosion resistance was calculated. By analyzing the macro and microstructure of the internal structures, appropriate mold materials were determined.

Tribological behavior of laser thermal sprayed Cr3C2–NiCr + 10%Ni/MoS2 composite coating on H13 hot work mould steel

Cr3C2–NiCr+10%Ni/MoS2 composite coating was fabricated on H13 hot work mould steel using a Laser Thermal Spraying (LTS). The friction–wear behaviors of obtained coating at 25, 400 and 700 °C were investigated using a ball–on–disc wear tester, and the effect of MoS2 on the lubrication in the friction–wear process was also discussed. The results show that the average coefficients of friction (COFs) of Cr3C2–NiCr+10%Ni/MoS2 coating at 25, 400 and 700 °C are 0.68, 0.55, and 0.35, respectively, and the corresponding wear rates are 25.97 × 10–6, 30.06 × 10–6, and 11.86 × 10–6 mm3 · N–1 · s–1, respectively. The average COF and wear rate at 700 °C are the lowest among the three kinds of operation temperatures, the MoS2 particles and oxidation layer play a positive role of lubrication, which is the main factor of friction–wear reduction. The wear mechanism at 25 °C is abrasive wear, while those at 400 and 700 °C are primary abrasive wear, accompanied by oxidative wear.

Endurance of Renewable Polymer Composite to UV Irradiation

Polymer degradation occurs under the influence of sunlight and almost all polymer require stabilization to resist the adverse effect. The polymer degradation leads to discoloration when exposed to ultraviolet (UV) irradiation. In this study the renewable polymer composite was produce by preparation of renewable monomer from waste vegetable oil, crosslink with polymethane polyphenyl isocyanate, distilled water and titanium dioxide (TiO2) as filler. The fabrication method of renewable polymer composite in which to produce RF and its composites (RFC) by manual casting method while for CR and CRC using hot compression moulding technique. The density, porosity and morphology structure of RF, RFC, CR and CRC were measured endurance to UV irradiation exposure for a period of 1000 hours by UV Whetherometer apparatus. The density of RF and RFC exhibit no significant changes after UV irradiation exposure while porosity shows decrease with increasing of percentage of TiO2 filler loading. The morphology structure measurement gives no significant changes of pore cell size of renewable polymer with the increased of filler loading and UV irradiation exposure by different fabrication technique. From observation, discoloration of RF and RFC is less dark as compared to CR and CRC. This is due to the different fabrication technique gives some effects for surface of renewable polymer due to application of heat during hot compression technique. The discoloration surface structure of RF, RFC, CR and CRC were changed from yellow to dark yellow colour after UV irradiation exposure. This is due to formation of quinone structure product produced from the photolysis of renewable polymer under UV irradiation exposure. Hence, TiO2 is used for UV absorber to delay discoloration on the surface of renewable polymer.Â

Quasi and dynamic impact performance of hybrid cross-ply banana/glass fibre reinforced polypropylene composites

Natural fibres has been in demand as a replacement of synthetic fibres. However, natural fibres have disadvantages such as low mechanical properties compared to synthetic fibres, weak matrix to fibre adhesion and low thermal stability. Therefore, using natural fibres as a single reinforcement is inadequate to satisfy the technical needs of the composite. Hybridisation between natural and synthetic fibres can enhance the properties by taking the advantages of each of the individual fibres. This paper presents the hybridisation effect between banana and glass fibre. The low-velocity impact performance of hybrid cross-ply banana/glass fibre reinforced polypropylene composites were investigated and compared with quasi static indentation. Four types of stacking sequences composites were manufactured using hot compression moulding method, and the test was carried out according to American Society for Testing and Materials (ASTM) D6264 for quasi-static indentation and ASTM D7136 for low-velocity impact. The results revealed that the incorporation of glass fibre in banana fibre reinforced composite leads to higher energy absorption and improved the overall impact performance.

Mechanical Properties of Thermoplastics Corn Starch (TPCS) Reinforced Pineapple Leaf Fibre (PALF) Composite

The aim of this study is to investigate the mechanical characterization of bio-composites on thermoplastic corn starch (TPCS) reinforced with 2 mm length of pineapple leaf fibre (PALF). The selection of different weight percentages of fibres (20, 30, 40, 50 and 60) weight percentage (wt.%) of PALF contents were applied in this study. The mixtures of TPCS with different wt.% of PALF were made by using a hot compression moulding at 165 °C for 15 minutes. The mechanical testing that has been performed are tensile, flexural and impact testing to determine the effect of fibre loading on bio-composites characteristics. The results show that by incorporating 40 wt.% loading of PALF, the tensile strength and tensile modulus has increased to the maximum. However, the flexural testing result shows that 50 wt.% loading of PALF show the highest strength and modulus. Meanwhile, the impact testing result shows decrement when the loadings of PALF increases. Scanning electron microscopy (SEM) show that the TPCS with 40 wt.% of PALF have a good miscibility between matrix/fibre in the bio-composites. Overall, the TPCS/PALF composites enhance the properties of the bio-composites for short-life application: that is, plate, container, disposable tray, packaging etc.

Electrochemical corrosion behavior of HVOF sprayed WC–12Co coating on H13 hot work mould steel

Purpose This study aims to investigate the electrochemical corrosion performance of high velocity oxygen fuel (HVOF) sprayed WC–12Co coating in 3.5 Wt.% NaCl solution, which provided a guiding significance on the corrosion resistance of H13 hot work mould steel. Design/methodology/approach A WC–12Co coating was fabricated on H13 hot work mould steel using a HVOF, and the electrochemical corrosion behaviors of WC–12Co coating and substrate in 3.5 Wt.% NaCl solution was measured using open circuit potential (OCP), potentiodynamic polarization curve (PPC) and electrochemical impedance spectroscopy (EIS) tests. Findings The OCP and PPC of WC–12Co coating positively shift than those of substrate, its corrosion tendency and corrosion rate decrease to enhance its corrosion resistance. The curvature radius of capacitance curve on the WC–12Co coating is larger than that on the substrate, and the impedance and polarization resistance of WC–12Co coating increase faster than those of substrate, which reduces the corrosion process. Originality/value The electrochemical corrosion behaviors of WC–12Co coating and substrate in 3.5 Wt.% NaCl solution is first measured using OCP, PPC and EIS tests, which improve the electrochemical corrosion resistance of H13 hot work mould steel.

Thermal properties of pineapple leaf/kenaf fibre reinforced vinyl ester hybrid composites

In this modern technology era, the usage of natural fibres has been widely used in various field of applications such as aerospace, maritime, military, automotive as well as structural building. This is due to the reason that they are lightweight, cheap, good sustainability and biodegradable. Only a small amount of research work being conducted on the hybridization of pineapple leaf and kenaf fibres reinforced with vinyl ester (PALF/KF/VE) hybrid composites. Thus, in this present work, the PALF/KF/VE hybrid composites are presented. The thermal properties of PALF, KF, VE as well as hybrid composites were investigated based on their structural components. PALF was in long fibre form while kenaf fibre was in woven form fabricated to form hybrid composites by using the hand lay-up and hot compression moulding. TGA testing was conducted to determine their respective thermal properties. From the experimental testing, the results showed that the thermal stability of hybrid composites enhanced rather than fibres themselves. The thermal degradation of PALF and KF occurred at the range temperature of 250-370°C while neat VE, PALF/VE and PALF/KF/VE occurred at 300-450°C. Thus, these composites can be used for various application such as automotive, aerospace, structural and others.

Characteristics and Tribological Behaviors of TiAlN/Cr-Ni Composite Coatings at Elevated Temperatures

A TiAlN/Cr-Ni composite coating was fabricated on H13 hot work mold steel using a cathode ion arc plating and laser cladding. The surface and cross-sectional morphologies, chemical compositions, phases and surface roughness of obtained coating were analyzed using a scanning electron microscope, energy disperse spectroscopy, x-ray diffraction and atomic force microscope, respectively, and the bonding strength was measured using a scratch test. The friction-wear properties of TiAlN/Cr-Ni coating at 400, 500 and 600 °C were investigated using a ball-on-disc wear test. The results show that the TiAlN coating is primarily composed of c-TiN and c-AlN hard phases, and the bonding strength of TiAlN coating with the Cr-Ni coating is 22.15 N. The average coefficients of friction of TiAlN/Cr-Ni coating at 400, 500 and 600 °C are 0.458, 0.318 and 0.449, respectively, and the corresponding wear rates are 0.329 × 10−3, 0.384 × 10−3 and 0.205 × 10−3 mm3 N−1 s−1, respectively, and the wear mechanism includes adhesive wear and oxidation wear.

Flame retardancy and mechanical properties of glass fibre reinforced polyethylene composites filled with novel intumescent flame retardant

A novel intumescent flame retardant (IFR) system composed of ammonium polyphosphate and poly (1,3-diaminopropane-1,3,5-triazine-o-bicyclic pentaerythritol phosphate) (APP/PDTBP) was mixed with polyethylene to prepare the continuous glass fibre reinforced polyethylene (CGF/PE) unidirectional prepregs by melt impregnation process, and then the CGF/PE/IFR composite laminate were consolidated by hot compression moulding method. The flame retardancy, thermal stability and mechanical properties of CGF/PE/IFR composite laminates were investigated by limiting oxygen index, vertical burning test, cone calorimetric test, thermogravimetric analysis, tensile and flexural strength tests, mode I interlaminar fracture toughness test, and scanning electron microscopy (SEM). The flame retardancy of CGF/PE composite laminates increased with the increase of IFR system loading, which attributes to the formation of intumescent char layer from flame retardants and the weakening of wicking actions of glass fibres. The mechanical properties increased and then decreased with addition of flame retardants, except for the flexural strength with continuous increase. The SEM images showed that IFR system had toughening effect and could improved the strength of fibre-matrix interface. Based on the mechanical properties and the flame retardancy, when the matrix contains 30 wt% IFR system, the CGF/PE/IFR composite laminate had the best comprehensive performance.

Development of bio-composite film based on high density polyethylene and oil palm mesocarp fibre

The aim of this study is to develop bio-film based on high-density polyethylene (HDPE) and oil palm mesocarp fibre (OPMF). Rheological and mechanical properties of the biofilm were investigated using melt flow index and tensile test respectively. The produced films were characterized using scanning electron microscopy and differential scanning calorimetry (DSC). In addition, biodegradation and absorption properties were studied. OPMF is dried and then added to HDPE to be compounded using a twin-screw extruder. Maleic anhydride was used as compatibilizer during the melt mixing. The film samples were prepared using hot compression moulding process. Young’s modulus was found to increase with addition of OPMF and vice versa for tensile strength and elongation at break of the film sample. The reason behind the reduction of tensile strength and elongation at break is the low effective cross sectional area of HDPE matrix. Melting point value was increased after the addition of OPMF into the film as shown in DSC analysis. The rising of water absorption rate of the films is greatly relative to the content of OPMF as a result of high affinity of OPMF to water.

Ply and interlaminar behaviours of 3D printed continuous carbon fibre-reinforced thermoplastic laminates; effects of processing conditions and microstructure

Taking advantage of an extended design and manufacturing space for composites, the technology of fused filament fabrication (FFF) of continuous fibre-reinforced thermoplastics shows great potential for the production of the next generation of lightweight structural parts. This process still has room for development. Moreover, knowledge of the mechanical behaviour of the resulting 3D printed composites is still limited. In this work, the intra- and inter-laminar behaviours of carbon fibre/polyamide printed laminates were extensively characterised to determine ply elastic and strength properties, as well as interface strength and fracture characteristics. Moreover, the effects of eventual production defects on these properties were analysed, putting in evidence some of the present shortcomings of the FFF process. Such defects include non-homogeneous fibre distribution, large amounts of intra- and interlaminar voids, and weak interlayer bonding, which are likely to be due to insufficient thermo-mechanical consolidation of the material during the FFF process, and have significant influence on the matrix-dominated mechanical properties. As a result, the transverse and interlaminar properties were found to be lower than those obtained through hot compression moulding of carbon fibre/polyamide laminates. Besides highlighting possible process improvements, the mechanical characterisation carried out in this work promises a significant contribution to the abilities of designing and simulating general 3D printed composite parts.

Effects of Hot Molding Parameters on Physical and Mechanical Properties of Brake Pads

Hot molding is one of the most important processes for the manufacture of friction materials in automotive brake systems. That is because it has direct impacts on the physical and mechanical properties. Porosity and compressibility affect properties like brake vibration. This then affects brake noise. Therefore, the objective of this work was to study the effects of hot molding conditions on the porosity and compressibility of friction materials. The crucial parameters; molding pressure, temperature and holding time were varied in the hot molding process. Porosity and compressibility were investigated and analyzed in relation to the manufacturing parameters using statistical analysis. The results and the correlation coefficients (R2) show that molding pressure and holding time are the most significant effects on porosity and compressibility. They indicate that the hot molding parameters can adequately explain porosity and compressibility.

Structural performance of poultry eggshell derived hydroxyapatite based high density polyethylene bio-composites

In this research, hydroxyapatite (HAp) was synthesized from chicken eggshell waste by hydrothermal method for the development of bio-composite material suitable for biomedical implant. However, since environmental influences on natural materials are unique for different geographical locations in the world, the use of agro wastes from these locations need to be investigated. This work provides the detail results of the potentials of eggshell as HAp source. High-density polyethylene (HDPE)/HAp composites were developed by random dispersion of Hap (10, 20, 30 and 40 wt.%) in HDPE matrix, and were designated as HAC10, HAC20, HAC30, and HAC40. The HAp-filled HDPE composites were developed by a hot compression moulding process. The samples were subjected to tensile, flexural, impact, fracture toughness and wear tests according to ASTM standards in order to establish their structural performance as an implant material. Furthermore, the samples were also tested for hydrophilicity using tap water and simulated body fluid (SBF). X-ray diffraction analysis showed strong peaks of hydroxyapatite phase which established that the influence of the selected processing conditions on the poultry eggshell as a natural source for the biomedical application was suitable for the synthesis of high-quality hydroxyapatite. The mechanical properties of the developed composites were enhanced to the level of the required properties expected of an implant material compared to the control sample except for impact strength. Water absorption characteristics of the developed composite samples also displayed expected behaviour in SBF solution than in tap water thereby promoting the material as a good implant material. From the results, the sample with 40 wt.% HAp possess the highest values in the mechanical properties examined while sample from 20 wt.% had the best fracture toughness. The results revealed that these waste eggshells could be successfully converted into useful biocompatible HAp particles needed for the enhancement of the mechanical properties of polymer composites to meet the structural challenges of bio-composites.

Study of Betel Nut Husk Fibre Reinforced Polymer Composite

The mechanical properties of oxo-biodegradable high-density polyethylene (oxo-HDPE) composites reinforced betel nut husk (BNH) fibre were studied in this research. A neat oxo-HDPE laminate and four betel nut fibre reinforced oxo-HDPE composites were fabricated using hot press compression moulding method. The composites contain 7%, 12%, 17%, and 22% fibres volume fraction respectively. The cross section of the composite was observed under scanning electron microscopy (SEM) and all five laminates are put through tensile test and hardness test. The result of the study shows that adding betel nut husk (BNH) fibres as reinforcement increases its tensile strength, specific tensile strength, and hardness of the composites. The good lamination observed under scanning electron microscopy (SEM) enable good transfer and distribution of stresses from the matrix to the fibres.