Fiber Reinforced Poly Lactic Acid Research Articles

Strong and thermal-resistance glass fiber-reinforced polylactic acid (PLA) composites enabled by heat treatment.

Polylactic acid (PLA) is a biodegradable polymer derived from renewable resources, showing potentials in replacing traditional petroleum-based polymers, yet its brittleness and low thermal-resistance limits its applications. Thus, glass fibers (GF) combined with heat treatment were used to prepare high-performance PLA. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were employed to analyze crystallization behavior of PLA/GF composite. Tensile, flexural and impact tests were conducted to investigate mechanical properties, and heat deflection temperature was measured to evaluate thermal resistance. GF can coincidently enhance strength, rigidity, and toughness of PLA. Isothermal heat treatment can further improve the mechanical properties regardless of GF content. Compared with neat PLA, the tensile strength, flexural modulus, and impact strength can be increased by 162.5%, 266.4%, 232.5%, respectively, in the presence of 20 wt% GF after isothermal heat treatment, and meanwhile heat deflection temperature can be increased from 50.6 °C to 148.8 °C. Both DSC and XRD analysis results indicated that GF can significantly enhance crystallization of PLA. Thus, not only GF but also enhanced crystallization led to the outstanding mechanical performance of PLA/GF composites. While GF shows little effect on thermal resistance, heat treatment can remarkably improve thermal stability, in particular for PLA/GF composites.

Water Absorption Behaviour and Mechanical Performance of Pineapple Leaf Fibre Reinforced Polylactic Acid Composites

Fast-growing scientific work is focusing on alternative sources to replace modern synthetic fibre materials due to the adverse effects caused by petroleum-based materials. Natural fibre possesses high potential as a replacement for synthetic fibre and petroleum-based products. These materials are not only greener and environmental-friendly, but also safe for human health. As such, this study investigated the influence of compatibilising agent of maleated anhydride polyethylene (MAPE) on mechanical performance of pineapple leaf fibre (PALF) reinforced polylactic acid (PLA). The raw materials, such as PALF, PLA, and MAPE, were mixed by using a hot roller mixer machine and hot compression moulding at 190ºC. The specimens were then tested for water absorption and flexibility. The specimens were submerged in water for 0, 7, 14, and 21 days. Three types of tests were conducted, namely water absorption, tensile, and flexural assessments. The results of water absorption, tensile, and flexural tests for the untreated PALF composite (UPALF) and treated PLAF composite (TPALF) were recorded and explained. As a conclusion, composite materials based on hydrophilic natural fibre may reduce the tensile and flexural properties of the composite.

A strategy for controlling degradation in vitro of carbon fiber-reinforced polylactic acid composites (by combining fiber modification and pulsed electromagnetic fields)

Carbon fiber-reinforced polylactic acid (C/PLA) composites are a human bone-fixation material, but control of the material’s degradation remains a major factor hindering its widespread use. In this study, a combined method for controlling the degradation performance in vitro of C/PLA composites was designed. In this strategy, carbon fibers for C/PLA composite reinforcement were prepared in both modified and unmodified forms. A pulsed electromagnetic field (PEF) was then selectively applied during the subsequent degradation process. Results and analysis showed that the interfacial ester bonding between modified carbon fibers and PLA matrices significantly affected degradation in vitro of C/PLA composite. However, PEF affected the degradation performance of C/PLA composites and, after PEF treatment, the material's water absorption, mass retention, and bending and shearing strengths were changed to varying degrees. This method, by combining fiber modification and pulsed electromagnetic fields (abbreviated as CMP) provided a new strategy for the controlled degradation of C/PLA composites in human skeletal fixation.

Effect of Extrusion Temperature on the Physico-Mechanical Properties of Unidirectional Wood Fiber-Reinforced Polylactic Acid Composite (WFRPC) Components Using Fused Deposition Modeling.

Wood fiber-reinforced polylactic acid (PLA) composites (WFRPCs) were used as a filament to manufacture the unidirectional WFRPC components by means of fused deposition modeling (FDM). The physico-mechanical properties of the WFRPC components printed at different extrusion temperatures (200, 210, 220, and 230 °C) were determined. The results revealed that most of the physical properties (moisture content, surface roughness, water absorption rate, and thickness swelling rate) of the printed WFRPC component were not significantly influenced by extrusion temperature, while its density and color difference increased as the extrusion temperature increased. Additionally, the tensile and flexural properties of the FDM-printed WFRPC component decreased when the extrusion temperature was more than 200 °C, whereas the compressive strength and internal bond strength increased by 15.1% and 24.3%, respectively, when the extrusion temperature was increased from 200 to 230 °C. Furthermore, scanning electronic microscopy (SEM) demonstrated that the fracture surface of the tensile component printed at a higher extrusion temperature exhibited a better compatibility at fiber/PLA interfaces and good adhesion between the extruded filament segments. These results indicate that the FDM printing process using different extrusion temperatures has a substantial impact on the surface color, density, and mechanical properties of the printed WFRPC component.

Accelerated thermal ageing behaviour of bagasse fibers reinforced Poly (Lactic Acid) based biocomposites

Ageing behavior is one of the crucial factor for selection of material by designers and engineers, mainly for structural applications. Investigation of the ageing effect on biocomposites would supplement current knowledge and may help in encouraging their uses in real life applications. The current experimental investigation aims to determine the variation in various properties of Bagasse fibers reinforced Poly Lactic Acid (PLA) biocomposites during accelerated thermal ageing. Specimens of biocomposite were fabricated and exposed to temperature cycles of −20 °C and 65 °C (12 h each) for 12 weeks and characterized after every 4 weeks of exposure. Tensile and flexural properties exhibited steady improvement on exposure up to 8 weeks, followed by a reduction after ageing for 12 weeks. It can be concluded from X-ray diffraction (XRD) and dynamic mechanical analysis (DMA) that significant change in crystalline and glass transition behavior happens during the exposure period.

THE EFFECT OF ALKALINE TREATMENT AND FIBER LENGTH ON PINEAPPLE LEAF FIBER REINFORCED POLY LACTIC ACID BIOCOMPOSITES

The awareness of natural fibers as alternative materials to synthetic fibers in composite applications have increased briskly due to lightweight, non-toxic, low cost and abundantly available. To-date, there are still limited works on fully biodegradable composites also known as biocomposites, especially using long pineapple leaf fiber (PALF) reinforced poly lactic acid biocomposites. Thus, this study presents an investigation of the effects of alkaline treatment and use of different fiber length on the mechanical performance of pineapple leaf fibers reinforced poly lactic acid, biocomposites. Flexural testing was conducted via ASTM D790. The results showed enhancement in flexural properties of the biocomposites when the PALF fibers were treated with alkaline treatment, suggesting an effect of improving mechanical interlocking between matrix and reinforcement due to rougher fiber surface. The flexural strength and modulus of long treated fibers increased from 56.47 MPa and 4.24 GPa to 114.03 MPa and 5.70 GPa respectively compared to long untreated fibers. Â In addition, the effect of fiber length is also proven to affect the overall performance of the biocomposites, in which the long PALF fiber composites exhibit superior flexural properties to those of the short fiber reinforced PLA biocomposites, i.e. flexural modulus of 5.7 GPa and 0.22 GPa for the long fiber composites and short fiber composites respectively. The existence of sodium hydroxide, (NaOH) on PALF fibers were confirmed by FTIR analysis. Surface morphology of both untreated and treated samples was studied by using a scanning electron microscope (SEM). Results from both analyses suggest removal of lignin and hemicellulose on the alkaline-treated PALF fiber reinforced composites led to a rougher fibers surface and formed a better fiber-matrix adhesion, as reflected in the flexural properties of the biocomposites as reported above.

Treatment of ramie fiber with different techniques: the influence of diammonium phosphate on interfacial adhesion properties of ramie fiber-reinforced polylactic acid composite

Ramie fiber-reinforced polylactic acid (PLA) composites were successfully prepared by hot compression molding. Different treatment techniques were used to modify the surface of ramie fiber. The influence of diammonium phosphate (DAP) on the interfacial adhesion between ramie fiber and PLA composites was investigated by the contact angle measurements, FTIR and SEM analyses. The contact angle measurement results showed that alkali treatment combined with DAP was very efficient in decreasing the hydrophilicity of fibers. After treatment, the hydrophilicity of untreated ramie fiber from 5.9 ± 1.3 decreased to 2.0 ± 0.8 mJ/m2. The wettability of alkali/silane/DAP-treated ramie fiber/PLA composite was higher (95.4° ± 1.3°) than that of pure ramie fiber/PLA composite (87.3° ± 1.9°). The FTIR results were consistent with the wetting measurements as the increment of hydrophilicity. Thermal analysis indicated that DAP-modified ramie fiber/PLA composites exhibited a lower thermal decomposition temperature, unique decomposition behavior and more residual char formation at decomposition temperature. The tensile, flexural and impact properties of DAP-modified ramie fiber composites were comparable to those of untreated ramie fiber composite. Moreover, proper alignment and uniform distribution of ramie fibers within the PLA matrix were found to be excellent. The morphological structures observed by SEM showed that well-modified ramie fibers enhanced the failure of the PLA composites in tensile, flexural and impact tests.

Hole making in natural fiber-reinforced polylactic acid laminates

Natural fiber-reinforced composite materials are finding wide acceptability in various engineering applications. A substantial increase in the volume of production of these composites necessitates high-quality cost-effective manufacturing. Drilling of holes is an important machining operation required to ascertain the assembly operations of intricate composite products. In the present experimental investigation, natural fiber (sisal and Grewia optiva fiber)-reinforced polylactic acid-based green composite laminates were developed using hot compression through film stacking method. The drilling behavior of green composite laminates was evaluated in terms of drilling forces (thrust force and torque) and drilling-induced damage. The cutting speed, feed rate, and the drill geometry were taken as the input process parameters. It was concluded that all the three input process parameters affect the drilling behavior of green composite laminates. The drill geometry was established as an important input parameter that affects the drilling forces and subsequently the drilling-induced damage.

Preliminary Study on the Mechanical Properties of Continuous Long Pineapple Leaf Fibre Reinforced PLA Biocomposites

This research work investigates the effect of using alkaline-treated continuous long pineapple leaf fibers (PALF) as reinforcement in bio-based poly lactic acid (PLA) polymer biocomposite. Alkaline treatment using NaOH solution was employed to improve the fiber-matrix adhesion, with the aim to enhance the mechanical properties of the biocomposites, in terms of its tensile and impact properties. In this study, both the plain PLA polymer and the PALF reinforced PLA biocomposites were prepared using compression moulding process. Thin films with nominal thickness of approximately 1 mm each were stacked in between continuous long PALF fibers prior to compression moulding via hot press machine to form biocomposites plate. Two types of mechanical testing were performed, i.e., tensile test (ASTM D3039) and impact test (ASTM D6110). Significant enhancements are observed when the plain PLA were reinforced with the PALF long fiber, with the biocomposites showing two times better the tensile strength and modulus, with the values of approximately 73.26 MPa in comparison to only about 34.85 MPa for the plain PLA and tensile modulus of approximately 2735.36 MPa in comparison to 1641.12 MPa for the plain PLA. The energy absorption of the biocomposites also showed promising results with a value of approximately 0.92 J/cm2 in comparison to only about 0.35 J/cm2 for the plain PLA. In addition, a scanning electron microscope (SEM) was used to scrutinize morphology of the PALF reinforced PLA biocomposites.

Experimental and theoretical investigation of prestressed natural fiber-reinforced polylactic acid (PLA) composite materials

Abstract In this work we demonstrate that the specific (weight-normalized) mechanical properties of polylactic acid (PLA) can be enhanced by leveraging a combination of (a) additive manufacturing (3D printing) and (b) initial post-tensioning of continuous natural-fiber reinforcement. In this study both tensile and flexural PLA specimens with different cross-sectional geometries were 3D-printed with and without post-tensioning ducts. The mechanical properties of two continuous reinforcing fiber strands (i.e., jute, flax) were experimentally characterized prior to threading, post-tensioning to a prescribed level of stress, and securing in place with 3D-printed anchors. The effect of fiber type, matrix cross-sectional geometry, number of reinforcing strands, and degree of post-tensioning on the specific mechanical properties (i.e., strength-, stiffness-, rigidity-to-weight) of PLA were investigated using both tensile and flexural mechanical testing. Experimental results confirmed that additive manufacturing alone can improve the specific tensile and flexural mechanical properties of PLA and that these properties are further improved via initial mechanical prestressing of natural fiber reinforcement. Data indicate increases of 116% and 62% for tensile specific strength and stiffness and 14% and 10% for flexural specific strength and rigidity, respectively, compared to solid, unreinforced PLA. A theoretical model of the prestressed composite tensile response was employed and found to accurately predict (

Mechanical and degradation properties of successive alkali treated completely biodegradable sisal fiber reinforced poly lactic acid composites

The natural fiber reinforced biodegradable polymer composites were prepared with short sisal fiber as reinforcement in poly lactic acid (PLA) matrix. The sisal fiber is treated with 10% NaOH followed by H2O2. The composites were prepared with untreated and treated short sisal fibers at different weight proportions up to 25% in PLA matrix and investigated for mechanical and degradation properties. The results showed that the composite with treated fiber at 20% fiber loading has shown 30% and 8% higher tensile strength than neat PLA and untreated sisal/PLA composite, respectively. The flexural strength of treated sisal fiber composite at same weight fraction was 17% higher than that of plain PLA. The impact strength of composite with untreated fibers at 25% fiber loading was 107% high compared to that of neat PLA whereas the impact strength of treated sisal composite was reduced with increased fiber loading. The water absorption was high for untreated sisal/PLA composite compared to all other composites in the present study. Untreated sisal/PLA composite has high thermal degradation temperature compared to composite with treated fibers but lower than that of pure PLA. The enzymatic environment has increased the rate of degradation of composites. Surface morphology of tensile fractured and soil degraded surfaces of the composites were observed using scanning electron microscopy.

Mechanical properties of bio-absorbable PLA/PGA fiber-reinforced composites

This study investigated important mechanical properties, the flexural strength and flexural modulus, of polyglycolic acid (PGA) fiber-reinforced polylactic acid (PLA) composites fabricated by melt-mixing. The flexural strength and flexural modulus were estimated using three-point bending tests conducted at 37°C. Both the flexural strength and flexural modulus were increased by PGA fiber reinforcement. Viscoelastic properties were also investigated using dynamic mechanical analysis (DMA) under tensile loading. Results show that PGA fiber, which acts as the nucleate agent of PLA, restrains the molecular chains of PLA. That restraint reduces deformation at the same stress condition, thereby improving the PLA flexural properties.

Thermo-mechanical performance of poly(lactic acid)/flax fibre-reinforced biocomposites

Abstract In this study, the thermo-mechanical performance of flax fibre reinforced poly lactic acid (PLA) biocomposites was investigated for the potential use in load bearing application such as body-in-white and body structures in the automotive sector. Focus was given into the relationships between the thermal and mechanical properties, and the material response under different loading and environmental conditions. The strength (72 MPa) and stiffness (13 GPa) of flax/PLA composites investigated indicate a very promising material to replace traditional choices in load bearing application. The PLA’s crystallinity was measured to approximately 27%. Annealing above 100 °C for an hour decreased that value to 30%, but analysis of tensile results of annealed specimens reveals a significant reduction of both the tensile strength and modulus. This reduction is associated with micro-cracking that occurred on the surface of PLA during the heating as well as deterioration of the flax properties due to drying. The study results show that strength and modulus increased with increasing strain rates, while elongation at break reduces respectively. A modulus of 22 GPa was recorded in 4.2 m/s crosshead velocity. Further, flax/PLA showed significantly higher modulus than flax/epoxy for the composites studied. Improvement of the interfacial bonding and the temperature characteristics, combined the thermoplastic nature of PLA, demonstrates that flax/PLA composites is ideal for use in structural automotive applications.

Bio-composites: Development and mechanical characterization of banana/sisal fibre reinforced poly lactic acid (PLA) hybrid composites

The work focuses on the influencing effect of fiber surface treatment by BP towards mechanical properties of BSF reinforced PLA composites. BSF were treated by BP to improve the adhesion between fibres and matrix. BSF (30 wt %) reinforced PLA (70 wt %) hybrid composites were fabricated by means of twin screw extrusion followed by injection molding process. Tensile strength, flexural strength and modulus were tested by means of UTM. The morphological analysis of the untreated and treated BSF reinforced PLA composites in comparison with virgin PLA was carried out by SEM to examine the existence of interfacial adhesion between BSF and PLA. The resultant data reveals that treated BSF restricts the motion of the PLA matrix due to better wettability and bonding. Consequently, mechanical properties like tensile and flexural moduli of BSF reinforced PLA composites were enhanced in comparison to virgin PLA and untreated BSF reinforced PLA composites. The results are discussed in detail.

The Influence of Alkaline Treatment on Mechanical Properties and Morphology of Rice Husk Fibre Reinforced Polylactic Acid

This study focuses on the influence of surface treatment and fibre sizes on mechanical behavior, physical properties and morphology of rice husk fibre (RHF) reinforced polylactic-acid (PLA). Modified RHF was prepared by using 6w.t.% sodium hydroxide (NaOH) and distilled water. PLA composite reinforced with 25w.t.% volume fractions of modified RHF was mixed using the internal mixer and fabricated by the mini injection moulding. Tensile and flexural strength results showed that the PLA composite with 100, 200 and 500μm particles sizes of water treated fibre are much higher than those of alkaline treated. DSC measurement was performed and indicated that the Tg, Tm and ΔHm of PLA reduced after reinforcement with water treated and alkaline treated fibres. TGA results showed that the treatment reduced the thermal stability of the PLA. FESEM micrographs for flexural fractured surfaces of composites showed micro crack and pores due to brittle fracture of the PLA matrix adjacent to the fibre as a result of the brittle nature of the PLA resin.

Effect of Triacetin on Tensile Properties of Oil Palm Empty Fruit Bunch Fiber-Reinforced Polylactic Acid Composites

The effects of triacetin as a plasticizer on the tensile properties and morphology of oil palm empty fruit bunch (EFB) fiber-reinforced polylactic acid (PLA) composites were studied. In this research, pulverized oil palm EFB fiber size from 0.25–0.50 mm were weighted with different fiber loadings and mixed with 5% triacetin. The obtained results indicated that the tensile strength and the Young's modulus of PLA/EFB composites with the addition of triacetin were enhanced at an 80% PLA and 20% EFB fiber loading. The interfacial properties between PLA and the EFB fiber were improved after the addition of triacetin.

Cytocompatibility and Mechanical Properties of Short Phosphate Glass Fibre Reinforced Polylactic Acid (PLA) Composites: Effect of Coupling Agent Mediated Interface.

In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ϕ = 20 µm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent’s within medical implant devices.

Effect of surface treatment on the morphology of sisal fibers in sisal/polylactic acid composites

Sisal fibers were pretreated by alkali and alkylation, and then mixed with polylactic acid to make sisal fiber-reinforced polylactic acid composites, respectively. The architecture and aspect ratio of sisal fibers before and after mixing, the micro-morphology of fracture surface, and the properties of composites were investigated. The results showed that surface treatment greatly impacted the fiber fracture behavior. Shearing fracture occurred to the untreated sisal fibers and alkali-treated sisal fibers, which led to a sharp reduction in the length of the fiber, while the shear-tear facture occurred to the alkylation-treated sisal fibers and resulted in obvious decrease in both length and diameter of alkylation-treated sisal fibers. The fiber aspect ratio of sisal fibers was affected first by the pretreatment method, then by the processing temperature, and the sisal fiber content. Furthermore, the mechanical properties of reinforcing fibers and sisal fiber-reinforced polylactic acid composites were influenced fundamentally by the pretreatment method.

The potential of wood fibers as reinforcement in cellular biopolymers

Wood fiber-reinforced polylactic acid composite foams have been successfully produced using supercritical carbon dioxide. The addition of fibers had a strong effect on microstructure of the foams. An increase in wood fiber content implied smaller average cell size and higher average cell wall thickness as estimated from image analysis of scanning electron microscopy micrographs. Addition of 10 wt% wood fibers seemed to be a limit to obtain foams, with the used processing conditions. The stiffness properties of the foams in compression improved upon addition of wood fibers. A significant increase of specific stiffness was achieved by adding 5–10 wt% wood fibers. It was shown that the stiffness was about 50% higher in the transverse direction for reinforced foams. The strength in the transverse direction increased for foams with unmodified wood fibers but decreased for foams with two types of treated wood fibers as compared with the strength of the pure polylactic acid foam of similar density. A butyl tetracarboxylic acid treatment followed by an additional surfactant treatment results in reduced wood fiber network-forming ability and reduced fiber–matrix adhesion. This contributes to the inferior observed strength properties in this study. The experimental stiffness was comparable with a superposed micromechanical model for a three-phase fiber-reinforced foam. The model shows that increasing the relative density, that is, the ratio of the density of the foam to the density of the composite material, by adding wood fibers results in a noteworthy increase in the transverse compression stiffness of the foams but only at relative density values above 0.2 for the used processing conditions in this study. The key factor for reinforcement is the relation between foam relative density and fiber volume fraction in the preform. The foaming conditions have to be adapted for each wood fiber content to obtain foams with the desired relative density.

Influence of surface treatments on structural and mechanical properties of bamboo fiber-reinforced poly(lactic acid) biocomposites

Bamboo fiber-reinforced polylactic acid (PLA) composites were prepared using a film-stacking process. Bamboo fibers were treated using three different methods, i.e., direct silane coupling (DC), silane coupling after plasma (CAP) treatment, and silane coupling during UV irradiation (CDU), to improve the interfacial bonding strength between fibers and PLA. After surface treatment, the chemical group on the surface of bamboo fibers was analyzed through Fourier transform infrared spectroscopy. The intensity of bands around 880–900 cm−1 increased strongly. These results suggested that the grafting of silane onto fibers was enhanced substantially. X-ray diffraction analysis indicated that the amorphous region of the CDU- and CAP-treated fibers increased. The interfacial shear strength between the fibers and the matrix also increased by 44.2%, 64.2%, and 87.4% by DC, CDU, and CAP treatment, respectively. In addition, the tensile strength of bamboo–PLA composites with DC-, CDU-, and CAP-treated fibers increased 43.0%, 61.1%, and 71.2%, respectively. Moreover, the predicted tensile modulus of the composites with CAP-treated fibers showed good agreement with the experimental one.