Increasing Fiber Length Research Articles

Исследование зависимости прочности при изгибе от длины и диаметра сапфировых волокон, полученных методом Степанова

Bending tests of sapphire fibers with different diameters from 220 to 410 μm at room temperature were investigated. Experimental dependences of strain at failure and fiber strength on length for different cross-section diameters have been obtained. Using the statistical Weibull distribution, the parameters of these dependences have been determined. On the basis of these parameters, a comparison of the dependences of the strength and strain of fibers at fracture on their diameter at different lengths has been investigated. It is established that the increase of strength occurs with the increase of fiber diameter. It is shown that, at a fiber length of 1 mm, the dependence of fiber strength on its diameter is the steepest, and the dependences are “smoothed out” with increasing fiber length up to 100 mm.

Effect of natural fish tail palm fiber on the workability and mechanical properties of fiber reinforced concrete

To improve the pre-cracking behavior and post peak strength of concrete composites, a new variety of natural fiber called Fish Tail Palm Fibers was used as micro reinforcement in concrete. Fish Tail Palm Fibers (FTPF) are completely renewable natural resources and are available in abundance, in many parts of the country including India. Three different volume fractions, (0.1%, 0.2% and 0.3%, and three different lengths of fibers (10 mm, 20 mm and 30 mm) were chosen as the parameters for investigation. Silane treated FTPF was added to concrete and the fresh and mechanical properties were studied. The slump values were slightly affected by the increase in volume fraction of fibers, as the viscosity of concrete increases with fiber content. The compressive strength of the control specimen was 30 MPa (M30). The maximum compressive strength, splitting tensile strength, and flexural strength of Fish Tail Palm Fiber Reinforced Concrete (FTPFRC) specimens are 36 MPa, 2.82 MPa and 4.2 MPa respectively, which were recorded for specimens with 0.2 Volume Fraction (VF) and 30 mm Fiber Length (FL). The increase in the compressive strength, splitting tensile strength and flexure strength is about 20 %, 22% and 30 % with the addition of 0.2 VF of fibers. The findings indicate that the incorporation of fish tail palm fibers reduced the work-ability of concrete. But the mechanical characteristics such as compressive strength, splitting tensile strength, flexural strength, and impact resistance were enhanced with the increase in fiber content and fiber length.

Investigations on Tensile and Flexural Behaviours of Fly Ash / Coir Reinforced Polymer Matrix Composites

HIGHLIGHTS Influence of Fly ash and Coir Fibre in mechanical performance of Polymer composite Polymers exhibits varying performance in tensile and flexural loading A threshold fly ash proportion has been limited to 5- 10%. Increasing fibre length shows improvement in strength whereas short fibre are good enough for modulus.

Investigation Of Dual-Pump Fiber Optical Parametric Amplifier Performance Driven by Energy Transfer Between Four-Wave Mixing Process

Fiber optical parametric amplifier (FOPA) is operated based on energy transfer from pump waves to signal wave and at the end of the fiber, an idler wave is generated. This process is called four-wave mixing (FWM). Even though effects of higher-order dispersion coefficients, fiber length, fiber nonlinearity, fiber attenuation, pump powers, pump wavelength separation and distance of central pump wavelength with ZDW on gain profiles have been examined by previous researchers, but on different fiber or numerically studied using the Optisys system, analytical model or different amplitude equations. Thus, in this study, the above-mentioned parameters on the gain performance of dual pump fiber optical parametric amplifier (FOPA) using highly nonlinear shifted fiber (HNL-DSF) as a medium will be numerically investigated using ode45 function in Matlab. The gain at a certain wavelength can be obtained by solving 4 coupled amplitude equations with fiber loss and pump depletion that govern the four-wave mixing (FWM) process of pumps, signal and idler waves. Simulations results indicate positive gives poor or no gain, meanwhile, an addition of to negative widens the bandwidth, but there is no significant effect with the addition of . Besides, an increase of fiber length, nonlinearity and pump powers improve gain performance, but an increase of fiber loss decays the gain amplitude. Increment of pump separation will enhance flatness of gain at wavelength far from central wavelength but results in an increase of gain reduction at the central wavelength. Lastly, must be positive, not too small and not bigger than 1.125nm to get a high, broader and lesser ripples gain.

Calculation of Bandwidth of Multimode Step-Index Polymer Photonic Crystal Fibers.

By solving the time-dependent power flow equation, we present a novel approach for evaluating the bandwidth in a multimode step-index polymer photonic crystal fiber (SI PPCF) with a solid core. The bandwidth of such fiber is determined for various layouts of air holes and widths of Gaussian launch beam distribution. We found that the lower the NA of SI PPCF, the larger the bandwidth. The smaller launch beam leads to a higher bandwidth for short fibers. The influence of the width of the launch beam distribution on bandwidth lessens as the fiber length increases. The bandwidth tends to its launch independent value at a particular fiber length. This length denotes the onset of the steady state distribution (SSD). This information is useful for multimode SI PPCF applications in telecommunications and optical fiber sensing applications.

An integrated approach to investigate age-related modifications of morphological, mechanical and structural properties of type I collagen

The main propose of this study is to characterize the impact of chronological aging on mechanical, structural, biochemical, and morphological properties of type I collagen. We have developed an original approach combining a stress-strain measurement device with a portable Raman spectrometer to enable simultaneous measurement of Raman spectra during stress vs strain responses of young adult, adult and old rat tail tendon fascicles (RTTFs). Our data showed an increase in all mechanical properties such as Young's modulus, yield strength, and ultimate tensile strength with aging. At the molecular level, Raman data revealed that the most relevant frequency shift was observed at 938 cm−1 in Old RTTFs, which is assigned to the C–C. This suggested a long axis deformation of the peptide chains in Old RTTFs during tensile stress. In addition, the intensity of the band at 872 cm−1, corresponding to hydroxyproline decreased for young adult RTTFs and increased for the adult ones, while it remained unchanged for Old RTTFs during tensile stress. The amide III band (1242 and 1265 cm−1) as well as the band ratios I1631/ I1663 and I1645 / I1663 responses to tensile stress were depending on mechanical phases (toe, elastic and plastic). The quantification of advanced glycation end-products by LC-MS/MS and spectrofluorometry showed an increase in their content with aging. This suggested that the accumulation of such products was correlated to the alterations observed in the mechanical and molecular properties of RTTFs. Analysis of the morphological properties of RTTFs by SHG combined with CT-FIRE software revealed an increase in length and straightness of collagen fibers, whereas their width and wavy fraction decreased. Our integrated study model could be useful to provide additional translational information to monitor progression of diseases related to collagen remodeling in musculoskeletal disorders. Statement of significanceType I collagen is the major component of the extracellular matrix. Its architectural and structural organization plays an important role in the mechanical properties of many tissues at the physiological and pathological levels. The objective of this work is to develop an integrated approach to bring a new insight on the impact of chronological aging on the structural organization and mechanical properties of type I collagen. We combined a portable Raman spectrometer with a mechanical tensile testing device in order to monitor in real time the changes in the Raman fingerprint of type I collagen fibers during the mechanical stress. Raman spectroscopy allowed the identification of the type I collagen bonds that were affected by mechanical stress in a differential manner with aging.

Mechanical Properties of Engineered Cementitious Composite Materials Using Different Types of Fibers

An Engineered Cementitious composite is an ultra ductile cementitious composite which is highly crack resistant, with a tensile strain capacity over that of normal concrete. In this study, three different types of PP. fibers are added to cement mortars with the aim to determine how they can be used to develop ECC materials. Fibers are used in different (aspect ratio, tensile strength and different proportions in volume fraction (1.0, 2.0, 3.0 and 4%)) in concrete mixture design. Hardened concrete properties, 28-days splitting tensile strength, flexural strength, cracking width were evaluated. Statistically significant effects were observed for polypropylene fibers on the splitting tensile and flexural strength, toughness indexes, and durability parameters showed an increase in the presence of polypropylene fibers. Increased fiber availability (fiber aspect ratio) in the concrete matrix, in addition to the ability of longer polypropylene fibers to bridge on the micro cracks, are suggested as the reasons for the enhancement in mechanical properties. Finally, crack width in fiber-reinforced concrete is calculated analytically with fiber property variables (fiber type, length, diameter and proportion). Results are compared with experimental values and concluded that with an increase in fiber length and/or decrease in fiber diameter crack width, decrease significantly

Investigation of bandwidth in multimode graded-index plastic optical fibers.

A new method is proposed for investigating the bandwidth in multimode graded-index plastic optical fibers (GI POFs). By numerically solving the time-dependent power flow equation, bandwidth is reported for a varied launch conditions (radial offsets) of multimode GI POF. Our theoretical results are supported by the experimental results which show that bandwidth decreases with increasing radial offset. This decrease is more pronounced at short fiber lengths. At fiber length close to the coupling length Lc at which an equilibrium mode distribution (EMD) is achieved, this decrease becomes slower, indicating that mode coupling improves bandwidth at larger fiber lengths. With further increase of fiber length, bandwidth becomes nearly independent of the radial offset, indicating that a steady-state distribution (SSD) is achieved. Such a fiber characterization can be applied to optimize fiber performance in POF links.

Experimental study on the mechanical properties of different fiber-reinforced seawater sea-sand engineered cementitious composites

Engineered cementitious composites (ECCs) are a type of fiber-reinforced cementitious composite featuring tensile multiple-cracking and strain-hardening behaviors. Fiber-reinforced seawater sea-sand engineered cementitious composites (SS-ECCs) are a new type of ECC used for construction in coastal and marine areas lacking fresh water and river or manufactured sand, offering SS-ECCs much potential and socioeconomic benefit. In this study, SS-ECCs were prepared with artificial seawater, natural sea-sand, different fiber types (polyvinyl alcohol (PVA) fibers, polyethylene (PE) fibers, polypropylene (PP) fibers) and different fiber lengths (6, 9, 12, and 18 mm). Compression, flexural, tensile and bending tests showed that the compressive and flexural strengths of SS-ECCs initially increased and then decreased with increasing fiber length. A fiber length of 12 mm yielded the maximum strength. The 12-mm PE fiber-reinforced SS-ECC displayed the largest ultimate tensile stress of 4.047 MPa and the largest ultimate tensile strain of 3.023%, and its flexural and tensile toughness indexes and residual flexural and tensile strength indexes all satisfied the corresponding requirements for an ideal elastoplastic material. In contrast, the 9 mm and 12 mm PVA fiber-reinforced SS-ECCs satisfied the requirements for an ideal elastoplastic material only partially. The relationship between the ultimate flexural deflection and the ultimate tensile strain is discussed, and the error of the formula between them is analyzed. All the findings can facilitate the future design and application of SS-ECCs in coastal and marine structures.

Function analysis of a cotton R2R3 MYB transcription factor GhMYB3 in regulating plant trichome development.

Cotton is an important fibre-producing crop. Cotton fibres consist of highly elongated trichomes derived from the ovule. To improve the quality of cotton, it is necessary to identify the genes regulating fibre development. GhMYB3 was identified through bioinfomatic analysis and introduced to Arabidopsis and cotton to observe the phenotype. Protein inteaction and promoter bingding assays were conducted to explore the role of GhMYB3 in trichome fibre growth. Cotton fibre development might share a similar regulatory mechanism to Arabidopsis leaf trichomes, which is determined by the essential regulatory complex, MYB-bHLH-WD40. The GL1-like R2R3 MYB transcription factor GhMYB3 interacts with the AtGL3 protein involved in Arabidopsis trichome development. Ectopic expression of GhMYB3 could rescue the glabrous phenotype of the Arabidopsis gl1 mutant and produced more ectopic trichomes on inflorescence stems and floral organs, confirming its orthologous function in plant trichome development. The expression of GhMYB3 increased in response to exogenous gibberellin (GA3 ), auxin (IAA) and methyl jasmonate (MeJA). Overexpression of this gene in cotton leads to a slight increase in fibre length and lint percentage, possibly by activating the transcription of its downstream gene GhRDL1 or other fibre-related genes. The results increase our understanding of the key role of GhMYB3 in positively controlling plant trichome development, and this gene could be a potential target for molecular breeding in cotton.

Study of silty sand slope protection from seepage flows using short fiber-sand mixtures

Silty sand slopes are prone to damage due to seepage or rainfall. A partial reinforcement method using short polypropylene fiber and sand mixtures was proposed to protect silty sand slopes from seepage flow failure. The effects and the reinforcement mechanism were explored. First, triaxial tests were performed on sand samples reinforced with fiber lengths (6 and 12 mm) and contents (0.25 and 0.50%) to verify the reinforcement effect. Then, model tests were conducted on sand slopes under lateral seepage flow and the failure mode with different fiber contents and reinforcement method were examined. The results showed that the cohesion and shear strength of sand were significantly improved with the increase of fiber content and length. The suction of unsaturated sand was also enhanced by the fibers. The change in stress-strain behavior from strain softening to strain hardening indicated that static liquefaction could be effectively prevented. The failure mode and extent of slope damage depended on the fiber content. However, it was noted that the slope surface with small reinforcement range performed similarly to that with large reinforcement range. In conclusion, the partial reinforcement method with short discrete synthetic fibers can be used as an effective alternative for slope reinforcement.

Insulin resistance limits corneal nerve regeneration in patients with type 2 diabetes undergoing intensive glycemic control.

Aims/IntroductionThis study aimed to investigate whether insulin resistance (IR) in individuals with type 2 diabetes undergoing intensive glycemic control determines the extent of improvement in neuropathy.Materials and MethodsThis was an exploratory substudy of an open‐label, randomized controlled trial of individuals with poorly controlled type 2 diabetes treated with exenatide and pioglitazone or insulin to achieve a glycated hemoglobin <7.0% (<53 mmol/mol). Baseline IR was defined using homeostasis model assessment of IR, and change in neuropathy was assessed using corneal confocal microscopy.ResultsA total of 38 individuals with type 2 diabetes aged 50.2 ± 8.5 years with (n = 25, 66%) and without (n = 13, 34%) IR were studied. There was a significant decrease in glycated hemoglobin (P < 0.0001), diastolic blood pressure (P < 0.0001), total cholesterol (P < 0.01) and low‐density lipoprotein (P = 0.05), and an increase in bodyweight (P < 0.0001) with treatment. Individuals with homeostasis model assessment of IR <1.9 showed a significant increase in corneal nerve fiber density (P ≤ 0.01), length (P ≤ 0.01) and branch density (P ≤ 0.01), whereas individuals with homeostasis model assessment of IR ≥1.9 showed no change. IR was negatively associated with change in corneal nerve fiber density after adjusting for change in bodyweight (P < 0.05).ConclusionsNerve regeneration might be limited in individuals with type 2 diabetes and IR undergoing treatment with pioglitazone plus exenatide or insulin to improve glycemic control.

Inter-annual effects of potassium/sodium fertilization and water deficit on wood quality of Eucalyptus grandis trees over a full rotation

In Brazil, most Eucalyptus plantations are located in regions experiencing periods of water shortage, where fertilizers such as potassium (K) are intensively used to achieve high productivity. Recently, sodium (Na) has also been considered a potential nutrient in K-deficient soils. K and Na supply can increase water stress in Eucalyptus grandis trees, which could negatively impact forest productivity over prolonged droughts. Wood properties are determinants of the quality and yield of products. They are important factors to consider when measuring the impacts of silvicultural practices and water deficit on forest productivity. However, alterations in wood properties due to interactions between K/Na fertilization, water availability, and stand age are not well documented.Through annual sampling of E. grandis trees throughout a complete rotation (6 years) in Brazil, we evaluated the interactive effects of K/Na fertilization, water availability, and stand age on stem volume, sapwood/heartwood ratio, wood density, fiber, and vessel features. We also evaluated the relationships between growth rate, wood density, and fiber and vessel features. The split-plot experimental design consisted of two water supply regimes (37% throughfall reduction versus undisturbed throughfall) and three fertilization regimes (K, Na, and control).Until six years of age, K and Na fertilization increased stem volume by 3 and 2-fold, respectively, and only K-fertilized trees affected stem volume by 37% throughfall reduction. Both K and Na detrimentally affected wood density and beneficially affected fiber length. The sapwood/heartwood ratio was highly and negatively related to the growth rate of trees. Wall thickness was not affected by either K or Na. As expected, K and Na affected vessel size due to an increase in basal area growth. However, the effects of Na were more pronounced than those of K. Significant interactions between fertilization and water availability suggest that, under water deficit, wood density will not be affected by K fertilization. In contrast, the effect of Na and control treatments were invariable regardless of water availability.The effects of fertilization on wood properties changed over time, with non-significant effects in the first year and stronger effects from two years of age of trees. The variations in wood density were strongly related to variations in the fiber wall thickness. High increases in basal area growth promoted by K and Na were not related to significant decreases in wood density, but they were related to increases in fiber length. These findings highlight the significant effects of K addition on stem volume without significant losses in wood quality, even under water stress over a complete rotation. The negative impacts observed on wood density and lower productivity in commercial E. grandis plantations with the use of Na as a substitute for K should be considered.

Investigation on Speckle-Free Imaging at the Output of a Multimode Fiber under Various Mode Excitation Conditions

Speckle-free imaging using a multimode fiber has been widely used for imaging systems. Generally, previous work has assumed that all the propagating modes of the fiber are uniformly excited, but the modal power distribution is actually affected by excitation conditions. Here, we propose the utilization of a modal analysis method to study the dependence of the speckle contrast on the modal power distribution by changing the tilt angle of the Gaussian beam and on the group delay time difference caused by different fiber lengths. The results of numerical simulations and experiments show that, with an increase in the tilt angle of the Gaussian beam, the modal power is transferred to higher-order modes and the maximum delay difference between excitation modes becomes larger. Therefore, the inter-mode interference effect is effectively weakened, and the speckle contrast is significantly reduced. The increase in fiber length will also make the delay difference between excitation modes larger and thus the speckle contrast is decreased. For the larger tilt angle of the Gaussian beam, only a shorter optical fiber is required to reduce the speckle contrast significantly. Our work further promotes the use of a multimode fiber to produce speckle-free patterns in laser imaging systems.

Role of hydrogen peroxide in intra-operative wound preparation based on an in vitro fibrin clot degradation model

Three per cent hydrogen peroxide (H2O2) is widely used to irrigate acute and chronic wounds in the surgical setting and clinical experience tells us that it is more effective at removing dried-on blood than normal saline alone. We hypothesise that this is due to the effect of H2O2 on fibrin clot architecture via fibrinolysis. We investigate the mechanisms and discuss the clinical implications using an in vitro model. Coagulation assays with normal saline (NaCl), 1% and 3% concentrations of H2O2 were performed to determine the effect on fibrin clot formation. These effects were confirmed by spectrophotometry. The effects of 1%, 3% and 10% H2O2 on the macroscopic and microscopic features of fibrin clots were assessed at set time intervals and compared to a NaCl control. Quantitative analysis of fibrin networks was undertaken to determine the fibre length, diameter, branch point density and pore size. Fibrin clots immersed in 1%, 3% and 10% H2O2 demonstrated volume losses of 0.09-0.25mm3/min, whereas those immersed in the normal saline gained in volume by 0.02±0.13 mm3/min. Quantitative analysis showed that H2O2 affects the structure of the fibrin clot in a concentration-dependent manner, with the increase in fibre length, diameter and consequently pore sizes. Our results support our hypothesis that the efficacy of H2O2 in cleaning blood from wounds is enhanced by its effects on fibrin clot architecture in a concentration- and time-dependent manner. The observed changes in fibre size and branch point density suggest that H2O2 is acting on the quaternary structure of the fibrin clot, most likely via its effect on cross-linking of the fibrin monomers and may therefore be of benefit for the removal of other fibrin-dependent structures such as wound slough.

Painful diabetic neuropathy is associated with increased nerve regeneration in patients with type2 diabetes undergoing intensive glycemic control.

Aims/IntroductionPainful diabetic peripheral neuropathy (pDPN) is associated with small nerve fiber degeneration and regeneration. This study investigated whether the presence of pDPN might influence nerve regeneration in patients with type 2 diabetes undergoing intensive glycemic control.Materials and MethodsThis exploratory substudy of an open‐label randomized controlled trial undertook the Douleur Neuropathique en 4 questionnaire and assessment of electrochemical skin conductance, vibration perception threshold and corneal nerve morphology using corneal confocal microscopy in participants with and without pDPN treated with exenatide and pioglitazone or basal–bolus insulin at baseline and 1‐year follow up, and 18 controls at baseline only.ResultsParticipants with type 2 diabetes, with (n = 13) and without (n = 28) pDPN had comparable corneal nerve fiber measures, electrochemical skin conductance and vibration perception threshold at baseline, and pDPN was not associated with the severity of DPN. There was a significant glycated hemoglobin reduction (P < 0.0001) and weight gain (P < 0.005), irrespective of therapy. Participants with pDPN showed a significant increase in corneal nerve fiber density (P < 0.05), length (P < 0.0001) and branch density (P < 0.005), and a decrease in the Douleur Neuropathique en 4 score (P < 0.01), but no change in electrochemical skin conductance or vibration perception threshold. Participants without pDPN showed a significant increase in corneal nerve branch density (P < 0.01) and no change in any other neuropathy measures. A change in the severity of painful symptoms was not associated with corneal nerve regeneration and medication for pain.ConclusionsThis study showed that intensive glycemic control is associated with greater corneal nerve regeneration and an improvement in the severity of pain in patients with painful diabetic neuropathy.

Theoretical and Experimental Investigation of the Effect of Pump Laser Frequency Fluctuations on Signal-to-Noise Ratio of Brillouin Dynamic Grating Measurement with Coherent FMCW Reflectometry.

Signal-dependent speckle-like noise has constituted a serious factor in Brillouin-grating based frequency-modulated continuous-wave (FMCW) reflectometry and it has been indispensable for improving the signal-to-noise ratio (S/N) of the Brillouin dynamic grating measurement to clarify the noise generation mechanism. In this paper we show theoretically and experimentally that the noise is generated by the frequency fluctuations of the pump light from a laser diode (LD). We could increase the S/N from 36 to 190 merely by driving the LD using a current source with reduced technical noise. On the basis of our experimental result, we derived the theoretical formula for S/N as a function of distance, which contained the second and fourth-order moments of the frequency fluctuations, by assuming that the pump light frequency was modulated by the technical noise. We calculated S/N along the 1.35 m long optical fiber numerically using the measured power spectral density of the frequency fluctuations, and the resulting distributions agreed with the measured values in the 10 to 190 range. Since higher performance levels are required if the pump light source is to maintain the S/N as the fiber length increases, we can use the formula to calculate the light source specifications including the spectral width and rms value of the frequency fluctuations to achieve a high S/N while testing a fiber of a given length.

Measurement on Spurious Phase Stability in Optoelectronic Oscillators

Long loop delay in optoelectronic oscillator (OEO) helps to achieve high Q factor, but it also produces narrowly spaced spurious modes, which is hard to be filtered out. To suppress spurious modes, dual-loop and inject-locking structures have been studied. Besides, feedforward technique may also be used for spurious suppression. The more stable the spurious phase relative to the principal mode in OEO, the better the suppression can be obtained. To assess the phase stability of spurious mode, we built up a phase measurement system using digital IF structure. OEOs oscillated at 10GHz with different fiber lengths were set up. The results showed that the stability of the spurious phase improved with the increase of fiber length. This article provided experimental evidence of a possible method of spurious suppression for future work.

Quantitative Morphometry of Elastic Fibers in Pelvic Organ Prolapse.

Pelvic organ prolapse (POP) is common among older women who have delivered children vaginally. While the pathophysiology is not fully delineated, POP can occur in part from insufficient repair of disrupted elastic matrix fibers. Quantification of structural changes to elastic fibers has not been described previously for POP. The goal of this paper is to present a validated technique for morphometric analysis of elastic fibers in vaginal tissue cultures from lysyl oxidase like-1 knock out (LOXL1 KO) mice with POP. The effect of LOXL1 KO, effect of POP, effect of culture, and effect of elastogenic treatment on the changes in elastin fiber characteristics were tested using vaginal tissues from wild type multiparous (WT), LOXL1 KO multiparous prolapsed (POP) and LOXL1 KO multiparous non-prolapsed (NP) mice. Our results show significantly higher mean aspect ratio, maximum diameter and perimeter length in POP compared to NP after 3 weeks of tissue culture. Further, treatment of POP tissues in culture with growth factors with previously documented elastogenic effects caused a significant increase in the mean area and perimeter length of elastic fibers. This technique thus appears to be useful in quantifying structural changes and can be used to assess the pathophysiology of POP and the effect of elastogenic treatments with potential for POP.

A Comparative Study of Pellet-Based Extrusion Deposition of Short, Long, and Continuous Carbon Fiber-Reinforced Polymer Composites for Large-Scale Additive Manufacturing

Abstract Pellet-based extrusion deposition of carbon fiber-reinforced composites at high material deposition rates has recently gained much attention due to its applications in large-scale additive manufacturing. The mechanical and physical properties of large-volume components largely depend on their reinforcing fiber length. However, very few studies have been done thus far to have a direct comparison of additively fabricated composites reinforced with different carbon fiber lengths. In this study, a new additive manufacturing (AM) approach to fabricate long fiber-reinforced polymer (LFRP) was first proposed. A pellet-based extrusion deposition method was implemented, which directly used thermoplastic pellets and continuous fiber tows as feedstock materials. Discontinuous long carbon fibers, with an average fiber length of 20.1 mm, were successfully incorporated into printed LFRP samples. The printed LFRP samples were compared with short fiber-reinforced polymer (SFRP) and continuous fiber-reinforced polymer (CFRP) counterparts through mechanical tests and microstructural analyses. The carbon fiber dispersion, distribution of carbon fiber length and orientation, and fiber wetting were studied. As expected, a steady increase in flexural strength was observed with increasing fiber length. The carbon fibers were highly oriented along the printing direction. A more uniformly distributed discontinuous fiber reinforcement was found within printed SFRP and LFRP samples. Due to decreased fiber impregnation time and lowered impregnation rate, the printed CFRP samples showed a lower degree of impregnation and worse fiber wetting conditions. The feasibility of the proposed AM methods was further demonstrated by fabricating large-volume components with complex geometries.