Composites Of Resin Research Articles

The effect of elevated temperature exposure on the fracture toughness of solid wood and structural wood composites

Fracture toughness of wood and wood composites has traditionally been characterized by a stress intensity factor, an initiation strain energy release rate (G init) or a total energy to fracture (G f). These parameters provide incomplete fracture characterization for these materials because the toughness changes as the crack propagates. Thus, for materials such as wood, oriented strand board (OSB), plywood and laminated veneer lumber (LVL), it is essential to characterize the fracture properties during crack propagation by measuring a full crack resistant or R curve. This study used energy methods during crack propagation to measure full R curves and then compared the fracture properties of wood and various wood-based composites such as, OSB, LVL and plywood. The effect of exposure to elevated temperature on fracture properties of these materials was also studied. The steady-state energy release rate (G SS) of wood was lower than that of wood composites such as LVL, plywood and OSB. The resin in wood composites provides them with a higher fracture toughness compared to solid lumber. Depending upon the internal structure of the material, the mode of failure also varied. With exposure to elevated temperatures, G SS for all materials decreased while the failure mode remained the same. The scatter associated with conventional bond strength tests, such as internal bond and bond classification tests, renders any statistical comparison using those tests difficult. In contrast, fracture tests with R curve analysis may provide an improved tool for characterization of bond quality in wood composites.

Kompozyty zywicy epoksydowej z modyfikowanymi bentonitami dla potrzeb przemyslu lotniczego

Kompozyty zywicy epoksydowej z modyfikowanymi bentonitami dla potrzeb przemyslu lotniczego

Flexural properties of sawdust-reinforced epoxy composites post-cured in microwaves

Epoxy resin was filled with sawdust to optimize the flexural properties of the composite for structural applications. In order to reduce costs, it will be necessary to fill as much sawdust as possible subject to maintaining sufficient strength of the composites in civil and structural applications. This project varies the percentage by weight of the sawdust in the composites. The sawdust particles were sieved into three different sizes, which were <425 µm, 425–600 µm and 600–1180 µm, respectively. Palm oil was also added to the composites of epoxy resin and sawdust as a plasticizer to improve the flexibility of the composites. After casting the composites to the moulds, they were cured at ambient conditions for 24 h. They were then post-cured in a conventional oven or microwave irradiation and subjected to flexural tests. It was found that the best percentage of sawdust, with particle size of <425 µm, and of palm oil, by weight that can be added to epoxy resin to give an optimum flexural modulus and flexural strength, as well as cost was 15% and 5%, respectively. The contribution of the study was that if flexural modulus was the most important factor to be considered in the applications of the composites, sawdust is a suitable filler. However, if the most sought after properties were the flexural strength then sawdust is not a suitable filler.

Addition-curable phenolic resin with arylacetylene groups: preparation, processing capability, thermal properties, and evaluation as matrix of composites

Ethynyl phenyl azo novolac resin with substitution extent of 100% (EPAN100) was synthesized by a two-step procedure, including coupling reaction between salicyl alcohol and diazonium sulfate of 3-ethynyl aniline to get 4-(3-ethynylphenyl) azo salicyl alcohol (EPAS), and its polycondensation reaction. EPAS and EPAN100 were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H-NMR), and gel permeation chromatography. The melt viscosity characteristics of the resin were investigated by TA AR2000 rheometer. The cure characteristics and cure schedule of EPAN100 were determined by differential scanning calorimetry (DSC) analysis and the FT-IR technique. The DSC curve of EPAN100 showed a cure exotherm between 120 and 280 °C with an enthalpy of 416 J g−1, which was far lower than that of 1079 J g−1 for polyarylacetylene resin (PAA). Dynamic mechanical analysis and thermal gravimetric analysis were used to investigate the thermal stability of EPAN100. The results showed that cured EPAN100 resin possessed significantly improved thermal stability and char-yielding property relative to novolac-type phenolic resin. The onset decrease temperature of storage modulus ( Tonset) and glass transition temperature ( Tg) were 350 and 400 °C, respectively. The 5% weight loss temperature ( Td5) was approximately 420 °C, and the char yield at 900 °C in nitrogen was approximately 79%. In comparison with PAA-matrix composites, the composites of EPAN100 resin presented much higher mechanical strength both at room and high temperature. Scanning electron microscope analysis showed that silica cloth/EPAN100 resin possessed better interaction between resin and fibers.

Mechanical properties of sisal natural fiber composites according to strain rate and absorption ratio

AbstractThe effects of strain rate and water absorption properties can be used to evaluate the environmental degradation of sisal fiber reinforced polymer–matrix composites. Composites of vinylester and epoxy resin, reinforced by sisal fiber, were manufactured using the RTM method. To examine how the mechanical properties change with different surface treatments of a fiber, three fibrous composites with nontreated, permanganate, and silane treatments were compared in this experiment. Material fracture occurred as the brittleness hardened due to an increase in strain rate. The tensile strength was the largest in the permanganate‐treated epoxy composites, while the untreated vinylester had high elongation and fracture energy. The highest tensile strength value occurred at a 30% absorption ratio. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

Autotransplantation of a maxillary first premolar to replace an ankylosed maxillary incisor: 7-year follow-up

To present the combined endodontic, surgical and orthodontic treatment of an autotransplanted maxillary first premolar for the replacement of an ankylosed maxillary incisor. This case report describes the autotransplantation of a maxillary premolar after the extraction of an ankylosed incisor in a 13-year-old boy. To allow better adaptation of the donor tooth, the buccal root of the first premolar was removed using a diamond bur and the denuded root site was filled with acid-etched composite resin. The palatal root canal was dressed with calcium hydroxide for 2 months before filling with gutta-percha. Autotransplantation of a remodelled maxillary first premolar was achieved to substitute for the ankylosed maxillary central incisor. Orthodontic treatment was performed to correct an Angle Class II malocclusion. Seven years after root canal treatment, the autotransplanted tooth and supporting tissues appeared healthy both clinically and radiographically and were functioning well. • Autotransplantation is a viable option for the treatment of a missing tooth or for the replacement of a traumatized tooth when there is a donor tooth available. • Autotransplantation of a premolar for replacement of a missing anterior tooth is sometimes a suitable alternative to conventional prosthetic rehabilitation or implant treatment in young individuals. • Proper combined endodontic and orthodontic treatment of autotransplanted teeth might be possible without periodontal complications.

Mechanical behavior of basalt fiber-reinforced and basalt fiber metal laminate composites under tensile and bending loads

This article examines the mechanical behavior of Basalt fiber-reinforced epoxy (BFRE) and a new type of fiber metal laminates (FMLs) composed of steel, aluminum, and BFRE named as Basalt fiber metal laminate (BFML) under tensile and bending loads. To study the effect of fillers in epoxy, the micro glass powder (MGP) was only added into the epoxy resin in BFRE composites at various volume fractions. It was found that the MGP had no significant effect on tensile strength, but it raised the stiffness and decreased the failure strain of BFRE. On the other hand, bending strength increased by adding MGP. BFML showed superiority in energy absorption via tensile strength. This FML had flexibility much higher than that of BFRE. Adding MGP or metal layer to basalt-reinforced composites improved the mechanical properties in tensile and bending loads. Selective bending specimens of BFRE are studied by SEM to show the positive role of MGP in raising the bending strength and further analysis of the nature of fracture surfaces. High fragmentation of matrix was obvious.

Effect of carbonization temperature on the structure and microwave absorbing properties of hollow carbon fibres

A series of polyacrylonitrile-based hollow carbon fibres (PAN-HCFs) were prepared by carbonizing polyacrylonitrile (PAN) hollow cured fibres at temperature ranging from 550 to 950 °C for 1 h in nitrogen. The effects of carbonization temperature on the structure, elemental compositions, surface electrical conductivity, electromagnetic parameters and reflectivity of PAN-HCFs were investigated. Results indicate that the obtained PAN-HCFs have not been graphitized and the C content and surface electrical conductivity increases as the carbonization temperature increases. The reflectivity of composites of PAN-HCFs and resin is −7.50 dB at 6.06 GHz and the band of the reflectivity under −5 dB is 6 GHz when the carbonization temperature is 750 °C.

Synthesis and Characterization of Highly Flexible Thermoplastic Films from Cyanoethylated Corn Distillers Dried Grains with Solubles

Corn distillers dried grains with solubles (DDGS) can be made into highly flexible thermoplastic films without the need for plasticizers. DDGS is an abundantly available coproduct of ethanol production that is inexpensive ($80-130/ton) compared to most of the polymers used for thermoplastic applications. In this research, oil-and-zein-free DDGS was cyanoethylated using acrylonitrile, and cyanoethylation conditions were optimized to obtain high percent weight gain of up to 42%. Cyanoethylated DDGS was characterized using (1)H NMR, FTIR, DSC, and TGA. Cyanoethylated DDGS was compression molded into thermoplastic films, and the tensile properties of the films were studied. It was found that DDGS films with elongation as high as 38% and strength of 14 MPa could be obtained without the use of any plasticizers. Alternatively, films with strength as high as 651 MPa but with relatively low elongation (2.5%) were obtained by varying the extent of cyanoethylation. This research showed that cyanoethylation could be a viable approach to develop biothermoplastics from biopolymers for applications such as packing films, extrudates, and resins for composites.

Influence of Carbon Nanotubes on Mechanical and Thermal Properties of Glass Fiber Reinforced Vinyl Ester Resin Composites

Carbon nanotubes (CNTs) were incorporated into glass fiber/ vinyl ester resins composites to improve their mechanical and thermal properties, especially the interlaminar shear and longitudinal compressive strengths which are belong to the matrix-dominanted properties and much weaker than the fiber-dominated properties. In this study, a higher temperature initiator was added to improve the polymerization degree and raise the transition temperature (Tg). Mechanical testing indicated that by adding 0.4 wt% CNTs, the nano-filled composites attributed to 21%, 16%, 10%, and 8% improvement in interlaminar shear strength, compressive strength, tensile strength and flexural strength with respect to their counterparts without CNTs, respectively. Moreover, Thermogravimetric analysis (TGA) also exhibits approximately 14°C higher decomposition temperature than those of conventional composites.

Properties of the glass fibre/interpenetrating polymer network composites based on novel naphthalene-contained bismaleimide and cyanate resin

To obtain attractive properties, the structure of interpenetrating polymer networks (IPNs) is made from 2,7-bis (4-maleimidophenoxy) naphthalene (BMPN) and 2,7-dihydroxynaphthalene dicyanate (DNCY) containing 0.11 mmol/mol Fe(AcAc) 3 and 2% nonylphenol. The glass fibre reinforced composites are made from the novel IPNs bismaleimide-triazine (BT) resin containing BMPN and DNCY. Two T g s and high storage modulus are shown in DMA curves of these composites. Two glass transitions could be detected between 250°C and 350°C, and the storage modulus show higher than 19,000 MPa. Opposed to composites of co-cure BT resin, the flexural property, dielectric property and moisture uptake value of composites are improved obviously due to the formation of IPNs structure for the composites. This composites show good flexural property, low dielectric constants (DC) and low moisture absorption.

Experiment Study on Nd: YAG Pulsed Laser Cutting Carbon Fibers Composites

Nd:YAG pulsed laser cutting carbon fibers reinforced epoxy resins composites was studied. HAZ and kerf width was made as evaluation index, as well as laser pulse energy, cutting speed, pulse duration and assistant gas pressure was made as controlled parameters. Ideal quality of cutting can be achieved by adjusting those parameters. The effect of each parameter was analyzed.

The Preparation and PhysicoChemical Study of Glass, Jute and Hybrid Glass-Jute Bisphenol-C-Based Epoxy Resin Composites

Glass-PA (EC-G-PA), Jute-PA (EC-J-PA), Glass-Jute-Glass (EC-GJG-PA), Jute-Glass-Jute (EC-JGJ-PA) composites of epoxy resin of bisphenol-C (EBC) have been prepared using a hand lay-up technique at 150°C under 27.58 MPa pressure for 6 h by using phthalic anhydride as a curing agent. EC-G-PA, EC-J-PA EC-GJG-PA and EC-JGJ-PA Possess 34, 41, 27 and 21 MPa tensile strength; 34, 27, 19 and 22 MPa flexural strength; 1.9, 1.0, 1.6 and 1.3 kV/mm electric strength and 4.2 × 1013, 1.2 × 109, 8.7 × 1011 and 4.0 × 1011 ohm.cm volume resistivity. Hydrolytic stability of the composites was tested against water, 10% aq. HCl and NaCl solutions at 35°C and also in boiling water. The percent water uptake, equilibrium time and diffusivity of the composites have been determined and discussed their possible applications.

The thermal and dielectric properties of high performance cyanate ester resins/microcapsules composites

Novel high performance bisphenol A dicyanate ester (BADCy) resins/poly(urea-formaldehyde) microcapsules filled with epoxy resins (MCEs) composites have been prepared. The effects of different contents of MCEs on the thermal and dielectric properties of cured BADCy were investigated using dynamic mechanical analyzer (DMA), thermalgravimetric analyzer (TGA) and broadband dielectric analyzer. The dielectric properties of BADCy/MCEs treated in hot water and hot air were also discussed. The morphologies of BADCy/MCEs composites were characterized by scanning electron microscopy (SEM). Results indicate that the appropriate content of MCEs can improve or maintain the thermal stability, the low dielectric constant and dielectric loss of cured BADCy mainly owing to higher conversion of cyanate ester (–OCN) groups. After aged in hot water and hot air, respectively, BADCy/MCEs composites with small content of MCEs can retain the low dielectric constant and dielectric loss.

Experimental Study on Crack Defects Formation in Polyarylacetylene Composites and Modification Improvement of Resin

Polyarylacetylene (PAA) resin is one among the ideal ablation materials, due to its high char yield and has been used to fabricate composite structures for solid rockets and missiles. However, the manufacturing quality of PAA composite is difficult to control. This article aims to reveal the formation mechanism of crack defect for PAA composite and presents an improvement method by resin modification. In this article, crack features and formation process of quartz fiber reinforced PAA composite were first studied, and the shrinkage and brittleness of PAA resin were evaluated to analyze the reason for crack formation. Furthermore, PAA resin modified by blending with phenolic resin was developed to reduce the crack defect. It is found that large curing shrinkage and extreme brittleness are the main reasons, which result in crack defect and poor mechanical performances of PAA. Moreover, PAA and phenolic (PF) blend was proved to be effective in raising ductility and reducing shrinkage, leading to the reduction of crack defect. Besides, the interlaminar shear strength of quartz fiber/PAA-PF blend composite increased twice as compared with quartz fiber/PAA composite.

Novel radiation-resistant glass fiber/epoxy composite for cryogenic insulation system

A new radiation-resistant epoxy resin system was developed that has low viscosity and long working time at 45 °C. The system consists of triglycidyl-p-aminophenol (TGPAP) epoxide, isopropylidenebisphenol bis[(2-glycidyloxy-3-n-butoxy)-1-propylether] (IPBE) epoxide and diethyl toluene diamine (DETD). Boron-free glass fiber composites of epoxy resin with different ratio of TGPAP/IPBE/DETD were prepared by vacuum press impregnation. The ratio of TGPAP/IPBE affected the working time and the viscosity at the impregnation. The mechanical properties of the composites at 300 K and at 77 K were measured before and after 60Co γ-ray irradiation of 1 MGy at ambient temperature. The γ-ray radiation scarcely affected the properties of the composites.

Cardanol biocomposites reinforced with jute fiber: Microstructure, biodegradability, and mechanical properties

This work aims at studying the preparation and characterization of composites of phenolic resin (matrix) based on cashew nut shell liquid, reinforced by natural jute fibers. The fibers were chemically modified using alkaline treatment with solutions of NaOH (5 and 10%) and bleached with sodium hypochlorite NaClO/H20 (1:1) at 60–75°C. The microstructure was investigated by Scanning Electron Microscopy to observe the fiber surface after the treatment. As a result, there was an improvement in the thermal stability of the fiber, which was verified by Thermogravimetric Analysis. The jute fiber composites showed an improvement in their mechanical properties due to chemical treatment with 5% NaOH. Their biodegradability level depended on the employed alkali solution concentration. This study is important to evaluate the application of the fibers as renewable materials. POLYM. COMPOS., 31:1928–1937, 2010. © 2010 Society of Plastics Engineers.

Tribological properties of polymer composites with diamond-like carbon flakes

Composites of epoxy resin with diamond-like carbon (DLC) flakes were fabricated. The DLC flakes were prepared from a DLC film deposited by chemical vapor deposition on an aluminum substrate. The tribological properties of composites were evaluated in air and water environments using a reciprocating friction tester and an AISI 440C mating ball. The friction coefficient of the epoxy composite decreased from 0.90 to 0.69 in air and from 0.71 to 0.29 in water with the addition of DLC flakes. The specific wear rate of the composite also decreased from 5 × 10 − 5 to 7 × 10 − 6 mm 3/N m in air and from 4 × 10 − 5 to 4 × 10 − 6 mm 3/N m in water. In contrast, the wear of the mating ball increased. Furthermore, the tribological properties of DLC flakes as an additive in water were evaluated. The suspension of powdered DLC in water reduced the friction coefficient of epoxy resin against the AISI 440C mating ball. Furthermore, the wear of the resin was negligibly small, although severe abrasive wear on the mating ball was observed.

High-performance aromatic thermosetting resins with hydroxyl and ethynyl groups

A novel hydroxyl-ethynyl-arene (HEA) resin was synthesized via Aldol condensation and Sonogashira reaction. The structure of the obtained resin was confirmed by the techniques of mass spectroscopy (MS), gel permeation chromatography (GPC), proton nuclear magnetic resonance spectroscopy (1H-NMR), Fourier transform infrared spectroscopy, (FT-IR) and elemental analysis (EA). Differential scanning calorimetry (DSC) results showed an exotherm at the temperature range of 187°C–245°C, attributable to crosslinking reaction of the acetylene groups. After thermal cure, the obtained cured resin possessed excellent thermal stability. Thermal gravimetric analysis (TGA) in nitrogen showed the Td5 (temperature of 5% weight loss) was about 400°C, and the char yield in nitrogen was about 78% at 900°C. The laminate composite of HEA resin was prepared and its mechanical and thermal properties were determined. The usefulness of the HEA resin as matrix for ablative composite was evaluated. Copyright © 2010 John Wiley & Sons, Ltd.

Resistance to fracture of endodontically treated premolars restored with glass ionomer cement or acid etch composite resin: An in vitro study

Aim: Due to the weakness of endodontically treated posterior teeth requires more strengthened restoration to withstand occlusal forces. The purpose of the present study was to determine and compare the resistance to fracture of endodontically treated maxillary 1 st premolars restored with different materials in mesio-occluso-distal (MOD) cavity preparations. Materials and Methods: MOD cavity preparations in 80 endodontically treated maxillary 1 st premolars were restored using four different methods. Fiber rings were filled with stone plaster and the teeth were placed into the plaster up to the level of cemento-enamel junction. The teeth were grouped according to restorative method, mounted in an Instrom T.T. machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. Result: The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. Conclusion: The resistance to the fracture of the teeth was the same when they were stored with glass ionomer cement as a base over which composite resin was placed. When the entire cavities were filled with glass ionomer cement, the resistance to fracture of the teeth decreased significantly compared with the acid etch resin technique.