Shape memory and mechanical characterization of polylactic acid wood composite fabricated by fused filament fabrication 4D printing technology

The present study focuses on fabrication and characterization of polylactic acid wood composite fabricated using fused filament fabrication 4D printing technology. The major tests performed to investigate the effect of nanosilica and nanoalumina included shape recovery rate, hardness, compressive strength, dynamic mechanical properties and Thermo-gravimetric analysis. The result of mechanical test indicated that the addition of 2 wt.% nanoalumina improved the hardness, compressive strength and flexural strength by 40 %, 25 % and 3.3 % respectively. On the other hand, the addition of 2 wt.% nanosilica improved the hardness, compressive strength and flexural strength by 60 %, 55 % and 10 % respectively. Further, the addition of nanosilica and nanoalumina improved the thermal stability and decreased the maximum shape recovery rate of wood polylactic acid composite. Nanosilica reinforced wood polylactic acid composite indicated a better choice as compared to nanoalumina reinforced wood polylactic acid composite in terms of mechanical properties, thermal properties and maximum shape recovery rate.     

Evaluating the effects of multi-walled carbon nanotubes on the mechanical properties of chopped strand mat/polyester composites

In this research, the influence of adding multi-walled carbon nanotubes at various contents on the mechanical properties of chopped strand mat/polyester composites was investigated. Initially, the effect of the sonication time on the dispersion of carbon nanotube at the highest weight ratio (0.5 wt.%) was inspected. To achieve this goal, a new technique based on scanning electron microscopy, which utilizes the burn-off test, was introduced to visualize the dispersion state of carbon nanotubes. Subsequently, the effect of addition of multi-walled carbon nanotube on the tensile and flexural properties of the fiber reinforced composites was studied. The results of mechanical tests showed that adding only 0.05 wt.% carbon nanotube enhanced the flexural strength of the hybrid composite by 45% while the tensile strength was not changed significantly. Improvements in the tensile and flexural moduli were also observed. Moreover, theoretical relations between the tensile, flexural and compressive moduli based on the classical beam theory were employed to determine the effect of carbon nanotube on the compressive modulus of composites. The theoretical result showed 31% enhancement in the compressive modulus.     

Mechanical and thermal properties of natural fibers reinforced polymer composites: Doum/low density polyethylene

Polymer composite materials with vegetable fibers were an attractive field for many industries and researchers, however, these materials required the issues of compatibility between the fibers and the polymeric matrix. This work evaluates the thermal and mechanical properties of Doum-fibers reinforcing a low density polyethylene (LDPE) composite to follow the effect of adding fibers into polymer matrix. Doum-fibers were Alkali treated to clean the fiber surface and improve the polymer/fibers adhesion. The Doum-fibers were compounded in LDPE matrix at various contents and extruded as continuous strands. An enhance on mechanical properties of composites was found, a gain of 145% compared to neat polymer at 30 wt.% fiber loading in Young’s modulus, a gain of 135% in flexural modulus at 20 wt.% fiber loading and a gain of 97% in torsional modulus at 0.1 Hz. Thermal properties were evaluated and the results show a slight decrease with increase of added Doum.     

Mechanical properties of poly(butylene succinate) (PBS) biocomposites reinforced with surface modified jute fibre

A biocomposite was originally fabricated with biodegradable polymer PBS and jute fibre, and the effects of fibre surface modification on characteristics of jute fibre and mechanical properties of the biocomposite were evaluated in this paper. The experimental results show that surface modification can remove surface impurities and reduce diameter of jute fibres. Regarding the mechanical properties of biocomposites, it is observed that the biocomposites with jute fibres treated by 2% NaOH, 2 + 5% NaOH or coupling agent, respectively, an optimum in mechanical properties can obtain at fibre content of 20 wt.%, which exhibit an obvious enhancement in mechanical strength and modulus compared to the ones with untreated jute fibre. Furthermore, surface modification also exhibits less effects on flexural properties compared to tensile properties and more on flexural or tensile modulus than on the strength.     

Mechanical and thermal properties study of glass fiber reinforced polyarylene ether nitriles

Glass fiber (GF) reinforced phenolphthalein-based polyarylene ether nitrile composites were prepared through melt blending, and the composites were characterized by various methods to find that both the mechanical and thermal properties of the silane coupling agent treated GF reinforced composites were improved with the increase of GF content. Tensile strength, flexural strength and Izod impact strength got their highest values with GF content at 35 wt.%, 30 wt.% and 25 wt.% respectively. The heat distortion temperature (HDT) of 30 wt.% GF reinforced composite is 284 °C, more than a 100 °C increase compared to the pristine resin.     

Combined effects of boron and compatibilizer on dimensional stability and mechanical properties of wood/HDPE composites

Thickness swelling, water absorption, and mechanical properties of the wood flour-high density polyethylene composites incorporated with different contents (4, 8, or 12 wt.%) of boron compounds (borax/boric acid and zinc borate) and compatibilizer (2, 4, or 6 wt.% maleic anhydride-grafted polyethylene (MAPE)) were investigated. The dimensional stability and mechanical properties of the uncoupled samples, except for the modulus of elasticity, were negatively affected by increasing the boron content while these properties were positively affected by increasing the compatibilizer content. The samples containing the zinc borate showed better dimensional stability and the flexural, tensile, and impact properties compared with the samples containing the borax/boric acid. The dimensional stability of the samples increased when the contents of the compatibilizer MAPE and boron compounds increased to 4% and 8 wt.%, respectively. However, a further increment in the content of the boron compounds (12 wt.%) negatively affected the dimensional stability and mechanical properties of the coupled samples (6 wt.% MAPE), except for the modulus of elasticity.     

Utilization of natural montmorillonite modified with dimethyl,dehydrogenated tallow quaternary ammonium salt as reinforcement in almond shell flour–polypropylene bio-nanocomposites

The main goal of this work was to evaluate the technical feasibility of almond shell flour (ASF) as wood substitute in the production of wood–plastic composites (WPCs). The effects of organically modified montmorillonite (OMMT), as reinforcing agent, on the mechanical and physical properties were also investigated. In order to improve the poor interfacial interaction between the hydrophilic Lignocellulosic material and hydrophobic polypropylene matrix, maleic anhydride grafted polypropylene (MAPP) was added as a coupling agent to all the composites studied. In the sample preparation, OMMT and ASF contents were used as variable factors. The morphology of the specimens was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results of mechanical properties measurements indicated that when 3 wt.% OMMT were added, tensile and flexural properties reached their maximum values. At high level of OMMT loading (5 wt.%), increased population of OMMT lead to agglomeration and stress transfer gets blocked. The addition of OMMT filler decreased the water absorption and thickness swelling of composites. SEM study approved the good interaction of the almond shell flour with the polymer as well as the effectiveness of OMMT in improvement of the interaction. TEM study revealed better dispersion of silicate layers in WPCs loaded with 3 wt.% of OMMT. The improvement of physico-mechanical properties of composites confirmed that OMMT has good reinforcement and the optimum synergistic effect of OMMT and ASF was achieved at the combination of 3 and 50 wt.%, respectively. The findings indicated that almond shell as agro-waste material is a valuable renewable natural resource for composite production and could be utilized as a substitute for wood in composite industries.     

Development and Characterization of the Midrib of Coconut Palm Leaf Reinforced Polyester Composite

In this paper, midrib of coconut palm leaves (MCL) was investigated for the purpose of development of natural fiber reinforced polymer matrix composites. A new natural fiber composite as MCL/polyester is developed by the hand lay-up method, and the material and mechanical properties of the fiber, matrix and composite materials were evaluated. The effect of fiber content on the tensile, flexural, impact, compressive strength and heat distortion temperature (HDT) was investigated. It was found that the MCL fiber had the maximum tensile strength, tensile modulus flexural strength, flexural modulus and Izod impact strength of 177.5MPa, 14.85GPa, 316.04MPa and 23.54GPa, 8.23KJ/m² respectively. Reinforcement of MCL enhanced the mechanical properties of pure polyester, including that of tensile strength (by 26%), tensile modulus (by 356%), flexural strength (by 41.81%), flexural modulus (by 169%) and Izod impact strength (by 23 times), but the compressive strength was adversely affected. HDT decreased due to fiber loading, but increased with weight fraction of fiber content. Moreover, the experimental results were compared with theoretical model (Rule of mixture) and other natural fiber /polyester composites.     

Hybrid bio-composite from talc,wood fiber and bioplastic: Fabrication and characterization

This investigation deals with the development of hybrid composites from wood fiber, talc and a bioplastic i.e., polyhydroxybutyrate-co-valerate (PHBV) using the extrusion–injection molding. Synergistic improvement in the mechanical properties of PHBV–wood fiber composites were obtained with the additional reinforcement of micro sized talc in it. The compositional design of hybrid green composites primarily focuses to create a balance among the cost effectiveness, the environment friendliness and the characteristics of the hybrid composites. The hybrid green composites showed a pronounced leap of 200% in the Young’s and flexural modulus with the dual reinforcement of 20 wt.% talc and 20 wt.% wood fiber in PHBV matrix. The dynamic-mechanical and thermo-mechanical properties of the composite were experimentally determined and show similar trend. The theoretical reasoning based on the surface energy parameters of the interacting components in the composite is elaborated to explain the reinforcing effect of talc and wood fiber. The Morphological analysis of the hybrid composite was carried out using the scanning electron microscopy (SEM), to study the interfacial interactions among the different components in the hybrid composite. The quantitative decrease of 36% in coefficient of linear thermal expansion, and the improvement in heat deflection temperature of the hybrid composite was also observed. This investigation was based on the structure–property-processing, co-relationships of the three components in order to obtain hybrid composites.     

Manufacture of a polymer-based carbon nanocomposite as bipolar plate of proton exchange membrane fuel cells

The aim of this paper is to prepare a polymer-based carbon nanocomposite reinforced by carbon fiber cloth (CF) to be utilized as bipolar plate of proton exchange membrane (PEM) fuel cell. For this purpose, some single, double, and triple-filler composites were manufactured by using phenolic resin as polymer (P) and graphite (G), carbon fiber (CF) and expanded graphite (EG) as fillers. The production method was compression-molding technique. The electrical conductivity, flexural strength, toughness, hardness, porosity, and hydrogen permeability tests were then measured to determine the mechanical and physical properties. A triple-filler composite containing 45 wt.% G, 10 wt.% CF, 5 wt.% EG, reinforced by a layer of CF cloth, was selected as composite bipolar plate. The electrical conductivity, thermal conductivity, and flexural strength of this composite were 74 S/cm, 9.6 W/m K, and 74 MPa, respectively, which are higher than the specified value by department of energy in USA (DOE). The composite bipolar plate used in the single fuel cell assembly showed a maximum power density 810 mW/cm². In this paper, a material selection was performed on the different materials of bipolar plates. It can be concluded that the composite bipolar plates are more suitable for high life time stationary applications.     

Effect of fiber loading on mechanical and morphological properties of cocoa pod husk fibers reinforced thermoplastic polyurethane composites

In this study, cocoa (Theobroma cacao) pod husk (CPH) fiber reinforced thermoplastic polyurethane (TPU) was prepared by melt compounding method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber loading: 20%, 30% and 40% (by weight), with the optimum processing parameters: 190 °C, 11 min, and 40 rpm for temperature, time and speed, respectively. Five samples were cut from the composite sheet. Mean value was taken for each composite according to ASTM standards. Effect of fiber loading on mechanical (i.e. tensile, flexural properties and impact strength) and morphological properties was studied. TPU/CPH composites showed increase in tensile strength and modulus with increase in fiber loading, while tensile strain was decreasing with increase in fiber loading. The composite also showed increase in flexural strength and modulus with increase in fiber content. Impact strength was deteriorated with increase in fiber loading. Morphology observations using Scanning Electron Microscope (SEM) showed fiber/matrix good adhesion.     

Effects of wood constituents and content,and glass fiber reinforcement on wear behavior of wood/PVC composites

In flooring applications, experimental data and insight from scientific investigations on wear properties of wood/polymer composites (WPCs) are important for engineers to understand how to design and formulate WPC materials with high resistance to wear. In this work, three different types of wood flour – namely Xylia kerrii Craib & Hutch., Hevea brasiliensis Linn., and Mangifera indica Linn. – were utilized and incorporated into poly(vinyl chloride) (PVC) with a fixed content (10 phr) of E-chopped strand glass fiber. The physical, mechanical and wear properties, in terms of specific wear rate, were then assessed as a function of wood content and sliding distance. The experimental results suggested that the addition of wood flour increased the flexural modulus and strength up to 40 phr; beyond this concentration, the flexural properties decreased. Hardness was not affected by the addition of wood flour. The mechanical and wear properties of WPVC composites were found to improve with the addition of the E-glass fiber. Xylia kerrii Craib & Hutch. wood exhibited the lowest specific wear rate for non-reinforced WPVC composites, whereas Hevea brasiliensis Linn. wood showed the lowest specific wear rate for the glass fiber reinforced WPVC composites. The longer the sliding distance, the greater the specific wear rate in all cases.     

Mechanical behavior of fire-resistant biocomposite

Biocomposites are typically formed by binding natural fibers derived from plants or cellulose using organic binders. The fibers that are used are normally industrial by-products and, hence, they are abundant and inexpensive. One such material is sawdust, and varieties of composite boards are being manufactured utilizing sawdust as filler material. Two major drawbacks of this system are their vulnerability to fire and very low bending strength. Both the matrix and the sawdust are flammable and this paper deals with using an inorganic matrix to improve the fire resistance. The inorganic matrix can resist temperatures up to 1000 °C and it provides protection to sawdust for short durations. The strength of these boards was increased by reinforcing with a very low percentage of high strength glass and carbon fibers. Since these fibers provide up to a fifteen-fold increase in strength, the cost increase is justifiable. Prisms were made using various proportions of sawdust ranging from about 11% to 38% by mass. The prisms were tested in compression and flexure to obtain the basic mechanical properties and determine the optimal sawdust content. Prisms with optimal sawdust content were also strengthened with glass or carbon fiber reinforcements to increase flexural capacity. The results indicate that it is possible to manufacture and engineer these types of composite beams to obtain a specified strength without using any specialized equipment, heat, or pressure, thus, producing an environmentally conscious biocomposite material.     

Physico‐mechanical characterization of garnet and fly ash reinforced Al7075 hybrid composite

The aim of present work was to study the effect of adding garnet and fly ash on the physical and mechanical performance of Al7075 hybrid composites. Al7075 hybrid composites reinforced with varying weight percentage (0 wt.%–15 wt.%) of each of garnet and fly ash were fabricated and characterized for the comparative assessment of their physical and mechanical properties. The physical and mechanical tests such as void content test, hardness test, tensile strength test, impact strength tests, flexural and fracture toughness test were performed for both garnet and fly ash reinforced composites. The finding of results indicated that the addition of 0 wt.%–15 wt.% of garnet increased the void content, hardness, flexural strength, tensile strength, impact strength and fracture toughness in the range of 1.01 %–2.69 %, 33 HRB–88 HRB, 165 MPa–275 MPa, 205 MPa–263 MPa, 12 J–22 J and 0.11 MPa ? m^1/2–0.58 MPa ? m^1/2 at crack length 0.1 respectively whereas addition of 0 wt.%–15 wt.% of fly ash increased the void content, hardness test, flexural strength, tensile strength, impact strength and fracture toughness in the range of 1.010 %–1.351 %, 33 HRB‐80 HRB, 165 MPa–225 MPa, 205 MPa–236 MPa, 12 J–20 J, 0.11 MPa ? m^1/2–0.48 MPa ? m^1/2 at crack length 0.1 respectively. Apart from the economic concern and void issue, Garnet indicated better choice of reinforcement as compared to fly ash in terms of mechanical properties.     

Effect of hybridization on the physical and mechanical properties of high density polyethylene–(pine/agave) composites

This work reports on the properties of high density polyethylene based hybrid composites made with two natural fibers: agave and pine. The composites were produced by a combination of extrusion and injection molding. The effect of hybridization was analyzed via morphological, mechanical and water immersion tests for two total fiber contents, 20 and 30 wt.%, and different pine-agave fiber ratios (100–0, 80–20, 60–40, 40–60 and 0–100). Moreover, the effect of coupling agent (maleated polyethylene) in the hybrid composite formulation was evaluated. The results showed that addition of agave fibers improves tensile, flexural and impact strength, while pine fibers decreases water uptake. As expected, the addition of a coupling agent improves substantially the quality of the polymer–fiber interface as well as the mechanical properties, but this effect was more important for composites produced with higher agave fibers content due to the their chemical composition.     

Development of slate fiber reinforced high density polyethylene composites for injection molding

During the last decade the use of fiber reinforced composite materials has consolidated as an attracting alternative to traditional materials due to an excellent balance between mechanical properties and lightweight. One drawback related to the use of inorganic fibers such as those derived from siliceous materials is the relative low compatibility with conventional organic polymer matrices. Surface treatments with coupling agents and the use of copolymers allow increasing fiber–matrix interactions which has a positive effect on overall properties of composites. In this research work we report the use of slate fiber treated with different coupling agents as reinforcement for high density polyethylene from sugarcane. A silane (propyltrimethoxy silane; PTMS) and a graft copolymer (polyethylene-graft-maleic anhydride; PE-g-MA) were used to improve fiber–matrix interactions on HDPE-slate fiber. The effect of the different compatibilizing systems and slate fiber content were evaluated by scanning electron microscopy (SEM), dynamic thermomechanical analysis (DTMA) as well as mechanical properties (tensile, flexural and impact). The results show that the use of silane coupling agents leads to higher fiber–matrix interactions which has a positive effect on overall mechanical properties. Interesting results are obtained for composites containing 30 wt.% slate fiber previously treated with propyltrimethoxy silane (PTMS) with an increase in tensile and flexural strength of about 16% and 18% respectively.     

Mechanical,sorption and adhesive properties of composites based on low density polyethylene filled with date palm wood powder

Low density polyethylene (LDPE) was blended with date palm wood powder (DPW) to prepare composites with concentrations of filler ranging from 10 to 70 wt.%. The Younǵs modulus of the composites significantly increased with an increase in the filler content in the entire concentration range. The maximum value of 1933 MPa for the composite filled with 70 wt.% of the filler is approximately 13 times higher than that for the neat LDPE.The presence of the filler improved the flexural strength, which was represented by the flexural stress at peak. The flexural strength of 17.8 MPa for the composite filled with 70 wt.% of the filler was two-times greater than that for the neat LDPE. The water absorption test revealed that the composites had a strong tendency to absorb water, which was dependent on the filler content. The experimental data were compared with several theoretical models.     

Investigation of rheological and mechanical properties of wood flour reinforced polypropylene

This study aims to investigate the rheological and mechanical properties of polypropylene when reinforced by wood flour. In the study, wood flour (WF) was added as filling material to polypropylene (PP), and its effects were investigated. The grain size of the wood flour was 300 μm. Wood flour was mixed into polypropylene material at different rates of weight. Viscosity changes of the polypropylene at various temperatures and pressure values of the concentration rates were documented. As a result, viscosity increases as the amount of wood flour filling is increased; yet as temperature, pressure and shear rate are increased, viscosity decreases. The study also focuses on the changes in its mechanical properties of polypropylene reinforced with wood flour. The tensile strength of reinforced polypropylene at varying percentages (wt. 5 %, wt. 10 % and wt. 15 %) was observed to decrease by 11 %, 16 % and 21 %, respectively, compared to that of non‐reinforced polypropylene. Additionally, impact tests showed that the highest energy absorption was in 10 % wood flour reinforced polypropylene.     

Effect of short nylon-6 fibres on natural rubber-toughened polystyrene

Composites based on polystyrene and natural rubber at a ratio of 85/15 were prepared by melt mixing with nylon-6 fibres using an internal mixer. The loading of short nylon-6 fibre, untreated and resorcinol formaldehyde latex (RFL)-treated, was varied from 0 to 3 wt.%. Tensile and flexural test samples were punched out from sheets and tested to study the variation of mechanical and dynamic mechanical properties. The tensile behaviour of the composite has been determined at three different strain rates (4.1 × 10⁻⁴ s⁻¹, 2 × 10⁻³ s⁻¹ and 2 × 10⁻² s⁻¹). Both the tensile strength and Young’s modulus of the composite increased with strain rate. The tensile strength, tensile modulus, flexural strength and flexural modulus increased with the increase in fibre content up to 1 wt.%, above which there was a significant deterioration in the properties. The RFL-treated fibre composites showed improved mechanical properties compared to the untreated one. Dynamic mechanical analysis (DMA) showed that the storage modulus of the composite with RFL-treated fibre was better compared to the untreated one. The fibre–matrix morphology of the tensile fractured specimens was studied by scanning electron microscopy (SEM). The results suggested that the RFL treatment of nylon fibre promoted adhesion to the natural rubber phase of the blend, thereby improving the mechanical properties of the composite.     

Effect of the addition of milled carbon fiber as a secondary filler on the electrical conductivity of graphite/epoxy composites for electrical conductive material

In this work, carbon composite bipolar plates consisting of synthetic graphite and milled carbon fibers as a conductive filler and epoxy as a polymer matrix developed using compression molding is described. The highest electrical conductivity obtained from the described material is 69.8 S/cm for the in-plane conductivity and 50.34 S/cm for the through-plane conductivity for the composite containing 2 wt.% carbon fiber (CF) with 80 wt.% filler loading. This value is 30% greater than the electrical conductivity of a typical graphite/epoxy composite with 80 wt.% filler loading, which is 53 S/cm for the in-plane conductivity and 40 S/cm for the through-plane conductivity. The flexural strength is increased to 36.28 MPa compared to a single filler system, which is approximately 25.22 MPa. This study also found that the General Effective Media (GEM) model was able to predict the in-plane and through-plane electrical conductivities for single filler and multiple filler composites.