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Mechanical properties of fiber reinforced additive manufacturing (FRAM) parts are affected by the fiber size and orientation. Oriented fiber composite is most likely to produce better properties. The objective of this research is to perform a comparative analysis of the mechanical properties of short and continuous fiber reinforced nylon 6 produced with fused filament fabrication (FFF) technology. In this study, it was observed that tensile, compression and flexural properties are significantly affected by the change in the fiber length and orientation. Scanning electron microscopy (SEM) was performed after mechanical testing to observe the influence of fiber on the final properties. From the testing, it was observed that continuous-FRAM (C-FRAM) parts show better properties in tensile loading and short-FRAM (S-FRAM) in bending. S-FRAM parts show better improvement in flexural and compression properties as compared to CFRAM parts. Morphological analysis of tested 3D-printed parts concluded that the fiber-pull out and fiber breakage are the main failure mechanisms.

Reported in this paper are the effects of tip-to-collector distance, voltage, deposition time and solution concentration on the fiber size distribution and filter quality factor of electrospun cellulose acetate (CA)-based nanofibers. Nanofibrous filter samples were produced by electrospinning in a laboratory setting. The CA solutions were prepared by diluting various concentrations of CA in a 2:1 (w:w) ratio of N,N-dimethylacetamide (concentration 10–20 wt.%). The electrospinning voltages ranged from 8–12 kV, with distances from 10–15 cm and deposition times of up to 30 minutes. The produced nanofibrous filter samples were then analyzed in terms of fiber size distribution and filter quality factor using nanosized sodium chloride particles ranging from 4–240 nm in diameter. The maximum filtration efficiency measured was 99.8% for filter samples obtained with an overall deposition time of 30 minutes. The maximum filter quality factor was 0.14 Pa−1 for a CA concentration of 20 wt.% and a tip-to-collector distance of 15 cm. The average fiber diameters of the fibers were between 175 and 890 nm, and CA concentrations below 15% led to the formation of beads.

To investigate the effects of mixing polypropylene fiber of different sizes and the effect of fiber size on the impact characteristics of concrete, two sizes of polypropylene fine fiber and one siz...

This work investigated the effect of maple fiber size and content on the auto-hybridization of linear low density polyethylene (LLDPE) composites. The samples were compounded by twin-screw extrusion and molded by compression molding. Different fiber loadings (5 to 20% wt.), fiber sizes (0-425 microns) and size ratios (30/70, 50/50, 70/30 of short, medium, and long fibers) were used to prepare the auto-hybrid composites with 3% of coupling agent (maleated polyethylene). Micrographs and impact strength results showed that the fracture in auto-hybrid composites is mostly dependent on the longer fibers. At 10% wt. the optimum ratio was 30/70 of shorter/longer fibers, which improved tensile strength (20%), tensile modulus (20%), and impact strength (13%) compared with composites with a single fiber size. But at 20% wt., tensile modulus increased by 30% and torsion modulus by 40% above the rule of hybrid mixtures (RoHM) at a 70/30 ratio of shorter/longer fibers.

Palm–based medium-density fibreboard (palm-based MDF) comprised of polyurethane prepolymer (pPU) and palm oil empty fruit bunch fibre (EFB) was prepared. The pPU was a reacting mixture in acetone consisted of palm kernel oil-based monoester polyol (PKO-p) and 4,4-diphenylmethane diisocyanate (MDI) with polyethylene glycol (Mw of 200 kDa, PEG200) as the plastisizer. EFB with size ranging from 250 μm to 500 μm (MDF S1), 500 μm to 1000 μm (MDF S2) and 1000 μm to 2000 μm (MDF S3) was investigated. The flexural strength and modulus increased with decreasing fibre size with optimum strength and modulus at 46.7 MPa and 1923 MPa respectively. Higher glass transition temperature (Tg at 77 °C) was observed in MDF S1 compared to MDF S3 (Tg at 67 °C). FTIR spectrum indicated possible formation of urethane linkage between the reactive NCO active groups in pPU with OH group from cellulose constituent in EFB fibre.

In this paper, the effects of fiber shape, fiber distribution, fiber size and fiber hybridization on the tensile properties of short sisal fiber-reinforced polypropylene composites were studied by the generalized method of cells and laminate analogy approaches. It is found that the fiber distribution has a large effect on the axial Young’s modulus. The fiber shape and fiber size have stronger influences on the transverse Young’s modulus and axial Poisson’s ratio than the fiber distribution. The fiber type hybridization and fiber shape are shown to be important factors in affecting the axial shear modulus. Hybridization with glass fiber is found to be an efficient method of creating high-performance composites.

Age-related changes in skeletal muscle, in combination with bed rest, may result in a poorer rehabilitation potential for an elderly patient. The purpose of this study was to determine the effects of non-weight bearing (hind limb unweighting [HU]) on the soleus and extensor digitorum longus (EDL) in older rats. Two non-weight bearing conditions were used: an uninterrupted bout of HU and an interrupted bout of HU. Twenty-one rats were randomly placed into 1 of 3 groups: control, interrupted HU (2 phases of 7 days of HU, separated by a 4-day weight-bearing phase) and an uninterrupted HU (18 uninterrupted days of HU). Following non-weight bearing, the soleus and EDL muscles were removed. Fiber type identification was performed by myofibrillar ATPase and cross-sectional area was determined. The findings suggest that any period of non-weight bearing leads to a decrease in muscle wet weight (19%-45%). Both type I and type II fibers of the soleus showed atrophy (decrease in cross-sectional area, 35%-44%) with an uninterrupted bout of non-weight bearing. Only the type II fibers of the soleus showed recovery with an interrupted bout of weight bearing. In the EDL, type II fibers were more affected by an uninterrupted bout of non-weight bearing (15% decrease in fiber size) compared to the type I fibers. EDL type II fibers showed more atrophy with interrupted bouts of non-weight bearing than with a single bout (a 40% compared to a 15% decrease). This study shows that initial weight bearing after an episode of non-weight bearing may be damaging to type II fibers of the EDL.

Introduction The extremely small fiber size and low mass of nanofiber composites makes quality control measurement very difficult. Most commercially available contact measurement equipment cannot work with the nanofiber composite without altering its characteristics. Generally, non-contacting optical methods are not effective because the wavelength of the light used is greater than the diameter of the nanofibers. Non-contact Gamma or Beta gauges lack the necessary resolution. Research methods such as Scanning Electron Microscopy (SEM) are not practical in a production setting. Large-scale production of nanofiber composites requires unique quality control (QC) methods. Figures 1a, 1b, and 1c show examples of nanofiber composites manufactured by Donaldson. As Donaldson Company’s nanofiber production has increased to over 10,000 m per day during the last 20 years, QC methods have been developed to address these needs. Four evaluation tools that have been developed for commercial production of nanofibers will be described. These evaluation tools focus on: uniformity of nanofiber distribution, fiber size distribution, durability of fiber layer in the composite, and environmental resistance.

Objective: The aim of this study was to analyze, morphologically and biochemically, one of the soft palate muscles, the levator veli palatini (LVP), in children born with cleft palate. Subjects and Methods: Biopsies were obtained from nine male and three female infants in connection with the early surgical repair of the hard and soft palate. Samples from five adult normal LVP muscles were used for comparison. The muscle morphology, fiber type and myosin heavy chain (MyHC) compositions, capillary supply, and content of muscle spindles were analyzed with different enzyme-histochemical, immunohistochemical, and biochemical techniques. Results: Compared with the normal adult subjects, the LVP muscle from the infantile subjects with cleft had a smaller mean fiber diameter, a larger variability in fiber size and form, a higher proportion of type II fibers, a higher amount of fast MyHCs, and a lower density of capillaries. No muscle spindles were observed. Moreover, one-third of the biopsies from the infantile subjects with cleft LVP either lacked muscle tissue or contained only a small amount. Conclusions: The LVP muscle from children with cleft palate has a different morphology, compared with the normal adult muscle. The differences might be related to different stages in maturation of the muscles, changes in functional demands with growth and age, or a consequence of the cleft. The lack of contractile tissue in some of the cleft biopsies offers one possible explanation to a persistent postsurgical velopharyngeal insufficiency in some patients, despite a successful surgical repair.

A method to fabricate flat laminates by filament winding was developed. Different fracture tests were then performed on materials with two different fiber size treatments. Based on the results, simple test methods sensitive to fiber size effects are suggested. Moisture conditioning was necessary for size effects to show.

A simple mathematical model has been developed to explain the mechanical behavior of a mono-fiber reinforced metal-matrix composite subjected to transverse loading. It is assumed that the metal-matrix material behaves as an elastic material at room temperature, and as a power-law creep material at elevated temperatures. In the model, material responses (stress, strain and displacement) are quantitatively described. The model predicts the effect of fiber size on failure mechanisms. Decohesion of the fiber/matrix interface is predicted to be easier as the fiber diameter increases, irrespective of test temperature. The model also predicts the location of void initiation which occurs away from the fiber/matrix interface at elevated temperatures. In addition, elongation was found to increase with increasing fiber diameter. Some qualitative experimental evidence supporting the theoretical predictions is presented.

Fiber size, pore size, and air permeability are three important properties in melt blown (MB) webs. Air permeability governs the air resistance or the pressure drop of the air through the web. One of the major applications of MB webs is for air filters. Fiber size dominates the web air filtration efficiency. Liquid filtration is another major application of MB webs. Pore size of the web determines the rated particle size in liquid filtration. Air permeability can be easily determined by air permeability testers. Fiber size and pore size in MB webs are difficult to measure by optical microscopy or other methods. However, they can be determined in fibrous products from the air flow rate through the web.

SummaryThe ATPase technique following preincubation in an acid medium (pH 3.8–4.0) was used to visualize capillaries. After preincubation at a pH of 4.5, in combination with the DPNH tetrazolium reductase, it was used to identify fiber types. A positive correlation has been demonstrated between fiber cross sectional area and C:F, indicating that large fibers are surrounded by more capillaries. The increase in fiber size may or may not be associated with changes in capillary density.

Biopsy specimens of skeletal muscle and peripheral nerve from two dogs with primary hypothyroidism but without clinical neuromuscular disease were studied with histological, histochemical and morphometric techniques. The most prominent change in skeletal muscle was variation in fiber size associated with a pronounced reduction in mean diameter of type II fibers. Type II fiber loss was apparent in the specimen from one dog. No histological or morphometric differences were noted in nerves from either dog compared with an age-matched control. The myopathic findings suggest a preferential metabolic defect in type II muscle fibers.

The effects of slack and tension mercerization on selected physical and accessibility characteristics of ramie were compared to the effects of the same treatments on flax and cotton. Slack mercerization of ramie and flax resulted in considerable losses in yam strength, while tension mercerization resulted in increased strength. Increased yarn strength was seen in both slack and tension mercerized cotton yarn. The effects of mercerization on ramie fiber cross-sectional parameters included increases in pe rimeter and area with no change in circularity. Little apparent change in fiber size or shape occurred in flax fibers, while the primary effect on cotton was increased circu larity. Increases in fiber accessibility were seen in all mercerized fibers, but the mag nitude of change in flax was approximately half of that in ramie and cotton. For all three fibers, the extent of swelling and modification in accessibility was greater under slack conditions.

A method previously reported for measuring shear friction of fiber assemblies was used for making a 5-week mill survey of samples that go routinely through the mill, for studying within and among bale variations and for examining some effects of growth environment. Some tentative interpretations are suggested. The shear friction was negatively correlated with span lengths and fiber tenacity. It was found to be sensitive to fiber size, shape, and finish on man-made fibers and to fiber orientation, as shown by differences in the shear friction values when the shear was executed parallel and then perpendicular to the direction of processing.

In observing the effects of stimulating a nerve in the body, it is possible to lead off the cut end of the nerve into the oscillograph and thus correlate the potential form with the functional result of stimulation. Since the different fibers of a nerve are stimulated at different threshold strengths, if the difference in thresholds of different fibers were known, the oscillograph or other potential recorder could be dispensed with except for an occasional observation of threshold for the most irritable fibers, and the experimental procedure thus simplified. With this end in view, we have examined the ratios between the threshold of the first fibers stimulated in a nerve and that of other fibers, taking as criteria the thresholds of the first fibers in the various potential waves which represent fiber size groups. Gasser and Erlanger1 have shown that the conduction rates of different fibers tend to vary as the fiber diameters, and by correlating the thresholds and conduction rates of different waves it sh...