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A conducting polymer, polyaniline (PANI), was synthesized in the presence of dispersed pulp fibers in the polymerization reaction to yield PANI/pulp composite fibers, which were then formed into a conducting paper sheet. The paper surface was observed using scanning electron microscopy, and electrical conductivity and electron spin resonance measurements were performed. This simple, convenient method for preparing organic conducting materials should prove useful for industrial applications, and the present results encourage further study in the new field of ‘textile electronics’. [ABSTRACT FROM PUBLISHER]

With the high precision requirements and the trend of large-scale composite parts, the development of composite molds is imminent. The short carbon fiber (SCF) composite mold is mainly prepared by the technological process flow of composite sheet injection, the bonding of composite plates, and machining. However, the current process optimization method has not matured adequately, and there are still many shortcomings, for example, low precision and high cost. In this paper, the optimization method of SCF/polyetherimide (PEI) composite molds is proposed. Many experiments have been conducted, and the results show that the coefficient of thermal expansion of composite samples can be effectively reduced and the mechanical properties can be improved by optimizing the SCF weight ratio and carbon fiber length. The bonding strength of composite joints in a high-temperature environment can be improved by optimizing the bonding process parameters and modification by carbon nanotubes. Based on the above optimization method, the SCF/PEI composite mold is prepared, and the C-shaped beam composite part is fabricated by using this mold. Compared with the part made by aluminum mold, the shape accuracy of the C-shaped beam composite part is proven high through digital measurement technology. [ABSTRACT FROM AUTHOR]

The process presented in the paper allows to produce bulk carbon fibre/thermoplastic composite parts with oriented continuous fibre to get specific mechanical loading constraints for structural parts. This fibre orientation allows to increase the mechanical strength of the composite product. This process consists of two steps: i) preforming and pre-consolidation necessary for the placement and orientation of the composite and ii) compression step. In this study, the first two steps are performed simultaneously by 3D printing. This study provides elements for optimizing certain process parameters and the associated results, particularly at different steps in the forming process. This paper also focuses on the movement of the material during shaping process. It links processing conditions and material characteristics, by determining the porosity and fibre ratio of composite part realized with different compression ratios. In addition, a repeatability study is conducted to identify the variability of the process and of the measurement method. [ABSTRACT FROM AUTHOR]

Tidal turbine infrastructure is currently in the large-scale prototype and short-term demonstration phase. However, the immediate requirement is to develop materials, processes and long-term life predictive facilities for tidal turbine plant that has decades of operational lifetime requirements. Computational modelling is a key tool to interpret the experimental data, understand the relevant mechanisms and provide a predictive capability for the performance of aged components for industries. The goal of this paper is a prediction of the long-term life of marine-based glass/epoxy and carbon/epoxy composite laminates aged in artificial seawater with 3.5% salinity based on Arrhenius degradation theory and tensile strength retention over 180 days ageing at room temperature and 60°C. Three different analytical models (linear and exponential) were implemented to calculate time shift factors and corresponding life in a real marine environment. Additionally, multi-scale modelling has been implemented via a representative volume element approach for square and hexagonal cells, and two-step homogenization of textile composites in accordance with nanoindentation testing for matrix/resin cells and fibre constraint cells after 90 days of immersion in saltwater. In general, the multi-scale modelling in ABAQUS and TexGen4SC was able to approximate (with about 10% difference) the mechanical properties of dry and aged composite laminates. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of the z-pin pre-hole inserted (ZPI) process on the impact resistance and post-impact flexural properties of skin/stringer composite structure with different z-pin parameters. The responses of the specimens are characterized in terms of impact denting & cracking length, load-carrying capacity, energy absorption and so on. Experimental results demonstrate that the z-pin cannot inhibit the initiation of debonding cracks at the skin/stringer interface. However, the z-pin forms a bridging traction zone across the cracking and prevent it from developing, which ensures the skin/stringer structure preserve higher peak loading and impact resistance. The specimens with the highest z-pin density have better impact resistance and outstanding residual flexural post-impact properties. Moreover, z-pins play a bridging role through its own failure. One is the inter-fiber debonding and splitting or shear failure of z-pins due to "snubbing effect," the other is the sliding friction of z-pins and z-pins' elastic deformation. These results could provide some guidance for designing z-pinning connection of composite skin/stringer structure. [ABSTRACT FROM AUTHOR]

The vacuum bagging is a common but critical step of various manufacturing process chains for Carbon/Glass Fibre reinforced polymers (C/GFRP). Whilst developing a new generation of vacuum bagging, significant efforts have been made to deeply understand the relevant physics fields, process variables involved and to provide predictive approaches to support dimensioning and scaling exercises prior to implementation into real production process. Main features of the new bagging system are, (1) the reduction of material diversity through merging of various properties within one single layer and, (2) the suppression of critical folding steps by using thermoforming for pre-shaping purposes. This paper will mainly focus on considerations of heat transfer during the pre-shaping of the film, directly on the CFRP part short before the curing step. For the better risk assessment of the short time exposition of an uncured composite part to the heat flow, a problem of transient coupled field analysis involving heat transfer via conduction, convection and radiation is formulated and solved by using Finite Element Analysis in COMSOL under consideration of realistic process conditions. Further a section dedicated to the comparison of the obtained results with measurements performed on a system including an IR-emitter, the bagging material, a ground plate and in some studies as well a CFRP sample is included. During the study the influence of time, power output of the emitter, distance between emitter and surface as well as irradiation angle has been assessed including a comparison of simulated results and performed measurements. [ABSTRACT FROM AUTHOR]

In this work, the analysis of the static behavior of the composite honeycomb and anti-trichiral sandwich is studied. The objective of this paper is to estimate the effect of cellular geometrical parameters which are the ligament length and the cylindrical node radius on the static properties of the anti-trichiral structures. The core and the sandwiches were made from the same biobased material which is polylactic acid with flax fibers (Flax/PLA Material). 3D printing technology was used to manufacture the specimens. Several tensile tests were performed on the anti-trichiral core while bending tests were carried out on the sandwich structures. Several specimens with different geometric parameters of the anti-trichiral unit cell are tested to study their effect on the static properties of this material. The results show that the static properties of the anti-trichiral shaped meta-material depend on the unit cell dimensions. The Poisson's ratio varies from 1 to −1 and from 0.5 to−0.8 respectively for one-cell and two-cell cores in width. To validate the experimental results, numerical simulations were carried out. Experimental and computational results for the Poisson's ratio were quite similar. [ABSTRACT FROM AUTHOR]

Control of energy expenditure in computer numerical control (CNC) machining is needed for eco-friendly operation of machining operations. Production industries deeply emphasize the improvement of productivity and saving in cost. The aluminum-based metal matrix composites (AMCs) can be substituted for metals for their mechanical properties in several applications. However, to bring in composite to usage, generally demand certain machining operation, which is quite challenging. This paper presents fabrication, characterization, and machining (turning) of Al-4032/6%GMP (granite marble powder) composite. Optical micrographs (OM) and scanning electron microscopy (SEM) with energy dispersive x-ray analysis (EDAX) have been used for the portrayal of the composite microstructure, surface topography, and fracture behavior. Also, mechanical characterization (tensile strength, micro-hardness, and impact strength) of the fabricated AMC has been carried out. The AMC samples have been examined for machinability for CNC turning operation. Cutting speed, feed rate, and depth of cut are the cutting parameters selected for the machining experiments. The response surface methodology (RSM)-based desirability function has been used to obtain the best combination of parameters for achieving the desired objectives. Experimental results demonstrate the built-up edge (BUE) formation on cutting insert and interfacial bonding of particles on workpiece surface at low cutting speed. Generally, smooth cutting operation has been observed at cutting speeds above 100 m/min. Best surface finish (1.38 μm) and minimum energy consumption (0.27 kWh) have been observed at cutting speed 176 m/min, feed rate 0.15 mm/rev, and depth of cut 0.45 mm. [ABSTRACT FROM AUTHOR]

This paper conducted experiments and theoretic analysis of the fracture performance of pultruded GFRP (Glass Fiber Reinforced Polymers) laminates. The mode-I fracture toughness of pultruded GFRP laminates was evaluated by the eccentrically loaded, Extended Compact Tension (ECT) specimen. The geometry of specimen and experimental procedure refer to ASTM E1922. A total of 16 specimens were tested, which included 0° and 90° roving orientation. Finite element analysis with the Virtual Crack Closure Technique (VCCT) was implemented to calibrate the experimental results. A correction function for normalized notch length was proposed for pultruded GFRP translaminar fracture toughness. Carpet plot was designed to discuss the relationship between fiber volume ratio and fracture toughness, which demonstrated that the fracture toughness strongly correlated with the fiber volume ratio. Also, the effect of fraction of 0° layers on fracture toughness and material orthotropy was studied. The relationship of material orthotropy parameter and fracture toughness was discussed. [ABSTRACT FROM AUTHOR]

The Air Force Research Laboratory led a research effort to benchmark the accuracy of static and fatigue predictions of several emerging composite progressive damage analysis techniques. The static portion of this technical effort is described in detail in a previous special issue of the Journal of Composite Materials. This paper provides the details of the fatigue experiments that were conducted to calibrate and validate the computational models. Initially, in-plane and out-of-plane S–N curves were generated through coupon tests that were performed on unidirectional laminae. The challenges experienced during fatigue testing of in-plane, matrix-dominated unidirectional coupon specimens are presented in detail. The higher fidelity test data from the fiber-dominated and out-of-plane experiments are also included in this paper. Following the calibration experiments, a series of tension–tension fatigue validation tests were conducted on open-hole coupons with three different stacking sequences. Each specimen was cycled to a pre-determined number of fatigue cycles, followed by static residual strength tests in both tension and compression. This paper provides the stress–strain responses of these validation tests as well as high-resolution X-ray computed tomography images of the subsurface damage as a function of cycles. Seven analysis teams used these test results to calibrate their models and to benchmark the accuracy of their predictions of damage and residual mechanical properties. [ABSTRACT FROM AUTHOR]

In this paper the results of an experimental investigation conducted on 76 mm (3 in) square hollow pultruded glass fiber-reinforced polymer (GFRP) tubes and their assemblies have been discussed. These GFRP tubes are used in the fabrication of an all-composite bridge deck that is designed for H-20 truckloads as specified by the American Association of State Highway and Transportation Officials (AASHTO). The study is principally focused on the experimental characterization of flexure performance under static loading of pultruded GFRP tubes made of unidirectional glass fibers. Several tests were conducted on single GFRP tubes followed by combinations of two tubes and a four-layered tube assembly. The tubes were bonded together using epoxy adhesive to build the assembly. The specimen details, experimental setup and instrumentation, testing procedure, failure modes and the test results of these experiments have been discussed in detail. A preliminary design model of each test coupon was developed and analyzed using Finite Element Analysis (FEA). Experiments were conducted to corroborate the analytical design model. Comparison between the theoretical and experimental results showed good correlation. Experimental results show excellent linear elastic flexural and shear behavior up to failure. The stiffness of the tubes and their assemblies demonstrate that they can be used in the building of all-composite bridge decks and for other infrastructure applications. Failure modes for the samples under static flexural loads are described. [ABSTRACT FROM AUTHOR]

The object of the static strength analysis presented in the following paper is an aerobatic airplane Harnaś-3. It is a new generation of an aerobatic airplane and its unusual arrangement makes it possible to make aerobatic maneuvers that are not possible to do by other airplanes. The untypical arrangement of the aerobatic plane Harnaś-3 causes that the strength analysis of its structure is particularly complex. A spatially developed structure requires a comprehensive approach, taking into account both the specific properties of composite materials and the need to analyze the strength ratio for various cases of external loads, appropriate for aviation regulations. The methodology presented in this article allowed to improve the structure of the Harnaś-3 aircraft to reach the weight of a complete structure of only 235 kg, which allows building an aircraft lighter than the competitors. [ABSTRACT FROM AUTHOR]

Recently, bonded composite patch repair, because of its significant advantages over traditional methods, has been highly accepted in several industries, particularly in aerospace applications. In this paper, a multi-scale finite element algorithm is proposed to simulate crack growth of repaired plates under fatigue load by considering the effects of composite micro-scale properties. The algorithm is verified through conducting an experimental set up and the proposed model is in reasonable agreement with experiments. The influences of different fiber volume fractions (VF), number of layers and fiber orientation of composite patch on the fatigue responses of adhesively bonded patch are investigated. For this purpose, Python scripts are written to automatically increase the size of the crack in ABAQUS. In this study, glass–epoxy and boron–epoxy patches are selected with volume fraction 0.1 to 0.7, the numbers of layers of 4, 8 and 16 as well as 5 different fiber orientation lay-ups. The maximum enhancement of fatigue life experimented by the variation of volume fraction is 133% in the mentioned range. Also, increment in the number of cycles by about 287% and 172% were seen per different number of layers and fiber orientation, respectively. [ABSTRACT FROM AUTHOR]

Waste marble dust is a solid waste generated during the cutting and polishing of marble pieces in construction sites and also in marble processing industries. This paper reports on the utilization of this waste as a filler material in particulate-filled polymer composite. Polyester-based composites are prepared with different weight proportions of waste marble dust and the dry sliding wear behavior of these composites is studied. Wear trials are conducted using a pin-on-disc test apparatus based on the Taguchi's L25 orthogonal array as per ASTM G 99-05. The effects of different parameters on the specific wear rate of the composites are studied and an optimum combination of parameters is obtained for the least wear rate. Based on the experimental data, a prediction model using the artificial neural network is used to predict the specific wear rate of the composites at a wider range of operating parameters, within and beyond the test region. The morphologies of the worn surfaces are studied by a scanning electron microscope to ascertain the wear mechanism of the composites at different conditions. This work thus opens up a new avenue for the value added utilization of a waste like marble dust in tribological applications. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of different tool pin morphologies on the inter-mixing capability, microstructure, mechanical properties, corrosion, fracture, and wear behaviors of the dissimilar friction stir welded AA6061-T6 alloy--Al 20wt% Mg2Si composite. Grooved shoulder tools with varying pin profiles such as tapered cylindrical, threaded tapered cylindrical, and triangular tapered pins were used for joining the base materials. The parameter combination of 80 mm/min travel speed and 1000 r/min rotation speed (at which no visible flow-induced defect was obtained) was used for this study. Among the pin profiles, the triangular tapered pin produced significantly improved intermingling/inter-material flow, fragmentation, and dispersion of the primary Mg2Si particles in the AA6061-T6/Al-Mg2Si joint. The triangular tapered tool reduced the average grain sizes of the AA6061 alloy and the Mg2Si particles from 18.4 to 4.6 µm and from 115 to 7.5 µm, respectively. Intermetallic phases of Mg2Si, AlFe, Al3.21Si0.47, and Al0.7Fe3Si0.3 are formed in the weld nugget of all the AA6061/Al-Mg2Si joints. The tensile strengths of the joints fabricated with tapered cylindrical, threaded tapered cylindrical, and triangular tapered tools are 108, 139, and 141 MPa, respectively. Abrasive wear is promoted in the joints fabricated with triangular tapered tool due to the homogeneous dispersion and fragmentation of the inherent hard Mg2Si particles. The corrosion attack is dependent on the fragmentation level of the Mg2Si phase. Triangular tapered pin tool is recommended for dissimilar Al/composite welding due to favorable tool-induced material flow, dispersion, and fragmentation of reinforcement. [ABSTRACT FROM AUTHOR]

Ultrasonic welding is a common fusion bonding technique to join unreinforced and reinforced thermoplastics. It is expected that applying ultrasonic vibrations to thermoset prepregs can produce heat generation to promote resin flow and consolidation. This paper discusses the feasibility of using ultrasonic vibrations as a high-speed repair technique for carbon fiber/epoxy prepregs to replace the traditional vacuum-bagging scarf setup. Three material types were investigated: out-of-autoclave unidirectional and plain weave prepregs (Cycom® 5320) and a general purpose twill weave prepreg (AS4/Newport 301). Two welding modes were considered: time and travel (vibrations stop once the desired vertical displacement is reached). For each mode, vibration time, travel, force, and amplitude were investigated. Cross-sectional analysis showed that void content equal to or below the vacuum-bagged samples could be achieved with ultrasonic consolidation to meet aerospace standards (≤2%). The following ultrasonic parameters were recommended to preserve prepreg tows integrity and minimize void content: vibration time below 1.0 s, travel between 12.5% and 50% of sample's initial thickness, force equal to or below 100 N, and amplitude below 41.3 μm. Temperature values recorded during the ultrasonic process reached the manufacturer's cure temperature range (120℃ to 180℃), with a predicted maximum degree of cure of 0.24. Interlaminar shear strength values were comparable for ultrasonically consolidated and vacuum-bagged samples. Soft and hard repair patches were applied to open-hole tensile coupons, with up to 50% strength recovery for both repair methods. Overall, ultrasonic consolidation has potential as a time- and cost-efficient repair method for thermoset prepregs. [ABSTRACT FROM AUTHOR]

In this paper, a new bi-tubular corrugated composite tube, consisting of inner and outer cylindrical and conical tubes is proposed. Different models with various geometrical parameters including the radius of curvatures and their numbers are considered and studied numerically in axial and oblique crushing in order to achieve favorable crashworthiness parameters. Moreover, quasi-static compression tests have been conducted to obtain results in order to validate the finite element model. There has been a sensible agreement between the numerical results and experimental data. Finite element models are also validated using the analytical solutions for both straight and corrugated composite tubes. Regardless of the number and radius of curvatures, as the crashworthiness of bi-tubular corrugated structures both in axial and oblique crushing is investigated and compared with their single-wall and bi-tubular straight peers, a considerable improvement is achieved in all crashworthiness parameters, including desirable increase in specific energy absorption, favorable reduction in peak force, and consequently a beneficial rise in crushing force efficiency. In addition, an optimization study using a suitable multi-objective function is done to choose the best model among the existing models, in addition to finding an optimum model via genetic algorithm. In the next step, a parametric study is conducted on the best model to inspect how well it undergoes oblique crushing at different angles. Finally, this best model and two other candidates have been chosen to investigate the effect of using foams and then the energy absorption capability of the empty and foam-filled tubes has been compared. [ABSTRACT FROM AUTHOR]

The bast fibres, a subgroup of natural fibre family, have emerged as a strong competitor of widely used man-made glass fibre for use as fillers or reinforcing materials in certain types of composite materials, which do not require very high mechanical resistance. This paper investigates the manufacturing of multi-layered jute fabric-reinforced thermoplastic composite and its mechanical performance. Hessian jute fabrics in two, four and six layers without any pre-treatment were sandwiched in 0° orientation into seven layers of high-density polyethylene sheets and pressed at high temperature and pressure to form composite laminates having three different structural designs. The laminates with two, four and six layers contain approximately 6.70 wt%, 12.90 wt% and 18.50 wt% of jute fibres, respectively. Mechanical performance of the composite laminates having four and six layers of jute fabric was found to have improved significantly when compared to the pure high-density polyethylene laminates. Within a given sample thickness of 6.5 mm, the laminate with six layers of jute fabric exhibited the best mechanical performance. Optical microscopic analysis revealed that the yarn orientation of the fabrics within the composites remained stable, and there was no visible void in the laminate structure. Fracture morphology of the composite investigated by a scanning electron microscope showed good adhesion of the jute fabrics with the high-density polyethylene matrix. [ABSTRACT FROM AUTHOR]

The design of modern mechanical components often requires the use of low-density and high-strength parts. Additive manufacturing presents competence in obtaining format complexity internally (voids, ducts, channels) and externally (shape, holes). However, parts obtained by material extrusion additive manufacturing are highly anisotropic and relatively weak. This paper aims to present a new mechanical design technique that combines the high geometry flexibility of additive manufacturing with internal structuring reinforcement by high-strength materials, which enables optimized parts with reinforcement in the most mechanical stressed areas during service, through adopting structured internal geometry filled with reinforcement material. Dense test specimens and test specimens with internal structural canals filled with reinforcement material (epoxy resin and carbon fibers) were designed, fabricated and tested physically and virtually. The obtained results provide property values for 3D-printed acrylonitrile butadiene styrene (typical material of additive manufacturing) and for this polymer reinforced with various reinforcement material configurations (useful for mechanical design). The reinforcement decreased anisotropy and improved mechanical properties. Optimized parts filled with resin and long carbon fibers had maximum flexural resistance of 112 MPa, with a specific weight of 1.1 g/cm3. This reinforcement provided parts with specific flexural strength similar to structural aluminum alloys, preserving the geometry and external dimension of the printed parts. The technique presented here shows the possibility of new conceptions in mechanical components design and strength optimization by internal reinforcement canals in parts. The technique is useful for mechanical design activity and allows for new product conceptions based on additive manufacturing. [ABSTRACT FROM AUTHOR]

In this paper, we set to examine the inter-laminar shear strength of a fiber-reinforced composite part manufactured via a stepped-concurrent ultraviolet curing and layering process. This process was specifically proposed for making epoxy-based thick parts, whereby a layer-by-layer, model-based, optimal layering time and ultraviolet control scheme is set up with the objective of minimizing the degree of cure deviation across the final thick part. We focus on a cationic curing process wherein additional energy savings are possible by switching off the ultraviolet source after initiating the curing reaction with the ultraviolet source at each layer addition. Since the inter-laminar sheer strength of parts made via a layering process is often a concern, we consider the application of in-situ consolidation pressure in the layering process. We then characterize the inter-laminar shear strength by manufacturing samples with application of different in-situ consolidation pressures and measuring the inter-laminar shear strength of each sample by the short-beam shear test. The results showed that the inter-laminar shear strength of composite parts fabricated with the proposed stepped-concurrent curing, and layering process increases with the applied consolidation pressure up to a point. Scanning electron microscopy of samples cured at different in-situ consolidation pressure showed that the sample with optimum consolidation pressure has relatively uniform fiber to resin distribution and hence improved inter-laminar shear strength. [ABSTRACT FROM AUTHOR]

A morphing leading edge produces a continuous aerodynamic surface that has no gaps between the moving and fixed parts. The continuous seamless shape has the potential to reduce drag, compared to conventional devices, such as slats that produce a discrete aerofoil shape change. However, the morphing leading edge has to achieve the required target shape by deforming from the baseline shape under the aerodynamic loads. In this paper, a conceptual-level method is proposed to evaluate the morphing leading edge structure. The feasibility of the skin design is validated by checking the failure index of the composite when the morphing leading edge undergoes the shape change. The stiffness of the morphing leading edge skin is spatially varied using variable lamina angles, and comparisons to the skin with constant stiffness are made to highlight its potential to reduce the actuation forces. The structural analysis is performed using a two-level structural optimisation scheme. The first level optimisation is applied to find the optimised structural properties of the leading edge skin and the associated actuation forces. The structural properties of the skin are given as a stiffness distribution, which is controlled by a B spline interpolation function. In the second level, the design solution of the skin is investigated. The skin is assumed to be made of variable stiffness composite. The stack sequence of the composite is optimised element-by-element to match the target stiffness. A failure criterion is employed to obtain the failure index when the leading edge is actuated from the baseline shape to the target shape. Test cases are given to demonstrate that the optimisation scheme is able to provide the stiffness distribution of the leading edge skin and the actuation forces can be reduced by using a spatially variable stiffness skin. [ABSTRACT FROM AUTHOR]

The design allowable values of composite materials were experimentally studied by specimen from two different suppliers, and the test data of grouped samples for bending strength, tensile strength, and interlaminar shear strength were obtained. The k-sample Anderson–Darling test method was adopted to analyze the test results, and the correlation conclusions of bending strength, tensile strength, and interlaminar shear strength were achieved. The test and analysis results show that the fluctuation range of bending strength, tensile strength, and interlaminar shear strength of composite specimen manufactured by the two suppliers is small, and the error range is less than 10.5%. The A-D test critical value ADC corresponding to bending strength, tensile strength, and interlayer shear strength is greater than the corresponding test statistical value ADK. The test data of the samples processed by the two suppliers have strong correlation, which can be considered to be from the same population. The above conclusions provide guidance of ideas and methods for the strength performance consideration of composite structure selection and substitution. [ABSTRACT FROM AUTHOR]

During the last decades, environmental concerns and limited resources have set focus of research on lightweight, mechanically high-performing structures for the transportation industry, in order to reduce fuel consumptions and CO2 emissions. Friction Stir Joining (FSJ), as a variant of the Friction Stir Welding (FSW), is an innovative friction-based joining technique for metal-composite hybrid structures. Joining in the plasticized state below the melting temperature of the metal leads to a comparatively small heat-affected zone, so that only minor metallurgical changes occur. Additionally, only a short processing time and no additional weight in form of fasteners is needed. The main objective of this study is to evaluate the feasibility of metal-composite structures via FSJ, intending to enable a macro-mechanical interlocking bonding mechanism. Main focus was given to the integration of an aluminium nub inserted in a carbon fiber-reinforced polyphenylene sulfide (CF-PPS) sheet, to ensure sufficient plasticization of the aluminium part and no degradation in the polymer part. Residual stress arising from the friction stir joining process was also characterised using the Contour method. In this study, aluminium alloy 6082-T6 and CF-PPS composite sheets were used to produce long lap joints. Results have shown that the joints were created at almost constant peak temperature slightly above the melting temperature of the PPS but no physical-chemical changes were detected in the PPS. In addition, the influence of a PPS film as interlayer between the sheets was investigated in order to explore a method for preventing galvanic corrosion. Preliminary results indicate that it is not possible to integrate a metal nub to the CF-PPS without interrupting the PPS film. However, it is possible to create a nub within the PPS film. [ABSTRACT FROM AUTHOR]

This paper reports properties of four different filaments prepared from (i) virgin polylactic acid, (ii) polylactic acid reinforced with polyvinyl chloride, (iii) polylactic acid reinforced with wood powder, and (iv) polylactic acid with reinforcement of Fe3O4 prepared with twin-screw extrusion for possible multimaterial three-dimensional printing. The results suggest that the melt flow rate of composite increases with the increase in reinforcements except for wood powder, which has shown a negative trend. Mechanical properties were also reduced with the loading but with the increase in the Fe3O4 content, these properties were improved. It has been observed that with reinforcement of polyvinyl chloride from 10 wt% to 25 wt% peak elongation and break elongation were reduced by 47.61% and 50%, respectively. Further, thermal analysis suggests that all samples were stable but for reinforced samples, the integral energy has decreased significantly in successive cycles. The vibration sample magnetometery of samples suggested that magnetic properties were dependent on the content of Fe3O4 present in the composite. [ABSTRACT FROM AUTHOR]

In this paper, the static and fatigue behavior of flax fiber-reinforced composites with and without an interleaved natural viscoelastic layer are investigated. Viscoelastic composite plates consist of a soft natural viscoelastic layer which is confined between two identical flax fiber reinforced composites. Different stacking sequences of specimens are tested with uniaxial tensile loading until failure. The mechanical behavior and the acoustic activity of damage sources in various configurations with and without a viscoelastic layer are compared. The analysis of acoustic emission signals and the macroscopic and microscopic observations led to the identification of the main acoustic signatures of different damage modes dominant in each type of composites (with and without a viscoelastic layer). These results allow better identification of the influence of the impact of a viscoelastic layer on the mechanical behavior of different composites. In addition, static and fatigue flexural behavior of unidirectional composites with and without viscoelastic layer are characterized in 3-point bending tests. The effects of viscoelastic layer on the stiffness, hysteresis loops, and loss factor are studied for various numbers of cycles during cyclic fatigue. [ABSTRACT FROM AUTHOR]

In this paper, bacteria belonging to the species Acetobacter xylinum were used to modify the surface of natural fibers by depositing nanosized bacterial cellulose around natural fibers which enhances their adhesion to renewable polymers. Single fiber tensile test was used in order to determine their mechanical properties and surface. The practical adhesion between the modified fibers and the renewable polymers cellulose acetate butyrate is quantified using the single fiber pullout test. Simple weight gain measurements before and after the modification show that about 4 and 6% bacterial cellulose adheres to the fibers as a result of the bacterial modification procedure. Scanning electron microscopy micrographs confirm the presence of attached bacterial cellulose on the surfaces of natural fibers. [ABSTRACT FROM AUTHOR]

In this paper, a quantum-behaved particle swarm optimization sliding mode control system (QPSOSM) is proposed to suppress the vibration of a multilayers composite material plate. Moreover, in this paper, fabricating a suppresser vibration setup box (SVSB) for the problem of an active vibration of a cantilevered 1-clamped 3-free composite plate is investigated. A mesh-free method is employed to create the shape functions. Also, the formulation of the problem is based on the classical laminated plate theory and the principle of virtual displacements. In this study, a function of the sliding surface is considered as an objective function and then the control effort is produced by the quantum particle swarm method and the sliding mode control strategy. At the end, the performance of the proposed QPSOSM control system and the fabricated SVSB controller are shown by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents an optimization of the mechanical properties of cement–Posidonia composite by means of experimental characterization. We are interested in producing composite of cement reinforced by Posidonia raw fibers. The ratio of fibers and water-to-cement mass is varied to determine its effect on the mechanical properties of the cement–Posidonia composite, particularly, its resistance to fracture. Three point bending and compression tests were carried out to study the mechanical properties of the composite. Scanning electron microscopy was used to examine the surface of the tested samples. The experimental investigation shows an improvement of flexural strength for a ratio W/C equal to 0.5 and fiber content equal to 10 vol%. [ABSTRACT FROM AUTHOR]

Tracking the variability of natural fiber-based fabrics properties, such as local areal weight, fiber volume fraction, and therefore permeability, is crucial to optimize the parts processing of the bio-composites. This paper aims at developing a cost-effective and efficient optical method in order to predict the permeability of flax fabrics used in liquid composite molding processes. This method using an LCD monitor as light source and a reflex camera as a measurement device is based on light transmission measurement through fabric thickness. The raw data given by the camera are gray scale maps, transformed into areal weight maps. FEM software based on levelset method is finally used to highlight the influence of the local variability of the fiber volume fraction, and of the related fabrics porosity and permeability on the mold filling time. The proposed method can be directly implemented on the manufacturing line of the composites. It can be used to optimize, part-to-part, the resin consumption by predicting the resin flow through perform. Interestingly, this novel optical method is auto-calibrated and does not depend on picture resolution. [ABSTRACT FROM AUTHOR]

Compared to the laminated composite made of two-dimensional preform, the three-dimensional-woven composites have been evolved as an attractive structural material. Based on the classical textile technologies such as weaving, braiding, and knitting, complex preforms have been fabricated as reinforcement for technical applications. In the recent years, many studies have been published on the development of modeling techniques to design, analyze, and understand the effect of the preform architecture on its mechanical behavior. In this paper, we propose to use these numerical approaches to evaluate the mechanical performance of multiaxis three-dimensional-woven preform. Also, comparisons of the estimated mechanical properties of this structure with that of 3D orthogonal-woven preform and that of classical laminate are conduced. [ABSTRACT FROM PUBLISHER]

Natural fibres have been widely studied as environment-friendly alternative to synthetic ones in composite manufacturing; they can be considered as reinforcement of geopolymeric foams for use as insulating materials. In this regard, the paper focuses on lightweight geopolymers reinforced with hemp fibre grids. These novel composite materials, produced in different ways, are characterized by means of wide experimental tests and their properties are compared with the ones of the plain geopolymer. Morphological analysis shows good bonding between the matrix and the hemp reinforcement; in addition, the main physical properties of the foam are not negatively affected by the presence of hemp fibres. From a mechanical point of view, the composites when subjected to quasi-static load conditions do not collapse in a brittle manner, and show improved flexural strength under dynamic load conditions. Finally, from thermal analysis, they guarantee a good thermal stability. [ABSTRACT FROM AUTHOR]

Voids are a concern in composite materials, as they may have a negative effect on the mechanical properties of the laminates. Voids may develop especially in low cost or off-optimum process conditions. In this study, samples of glass reinforced epoxy laminates with void volume fractions in the 0.5–7% range were successfully obtained by varying the vacuum in the hand layup vacuum bagging manufacturing process. Void content was experimentally characterized using four different methods: ultrasonic scanning, epoxy burn off, serial sectioning, and X-ray computed tomography. The goal of this paper was to determine how the methods compared with respect to each other at quantifying void content. The specimens were taken from nearby locations in the same panels, so a true comparison of the methods could be obtained. The results showed, for the specific material and manufacturing conditions used, that the four different techniques can quantify voids content but with a large variation in the accuracy. X-ray computed tomography was the most successful technique to characterize voids, followed by serial sectioning. Ultrasonic scanning and epoxy burn off were not recommended techniques to characterize voids for laminates manufactured with these materials and process conditions. However, epoxy burn off was a successful technique to calculate fiber and resin weight fraction. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic first ply failure analysis of composite laminates using a high-fidelity multi-scale approach called M-SaF (Micromechanics-based approach for Static Failure). To this end, square and hexagonal representative unit cells of composites are developed to calculate constituent stresses with the help of a bridging matrix between macro and micro stresses referred to as the stress amplification factor matrix. Separate failure criteria are applied to each of the constituents (fiber, matrix, and interface) in order to calculate the damage state. The successful implementation of M-SaF requires strength properties of the constituents which are the most difficult and expensive to characterize experimentally, limiting the use of M-SaF in the early design stages of a structure. This obstacle is overcome by integrating a Bayesian inference approach with M-SaF. An academic sample problem of a cantilever beam is used to first demonstrate the calibration procedure. Bayesian inference calibrates the M-SaF first ply failure model parameters as posterior distributions from the prior probability density functions drawn from lamina test data. The posterior statistics were then used to calculate probabilistic first ply failure for a range of different laminates. [ABSTRACT FROM AUTHOR]

Aircraft composite structures are widely joined using bolts. Differences in the tightening process parameters for tightening bolts can significantly affect the tightening torque (T)-preload (F) relationship. Some of the more significant process parameters include lubrication conditions, tightening speed, tightening area, sealant and washer. The experimental study compared the differences in T-F curves, friction coefficients, torque coefficients and yield preload during the tightening process for different values of the process parameters. The focus was on the state of the thread surface, the state of the bearing surface, the diffusion of the lubricating medium and sealant with preload, etc. The distribution of the T-F curve was obtained for all possible values of the process parameters. As the tightening speed increases, both the inter-thread friction coefficient and the macroscopic increase in the coefficient of friction on the bearing surface are observed when tightening the bolt head. The presence of sealant reduces the inter-thread friction coefficient. The size of the T-F curve area reflects the sensitivity of the bolt tightening process to the various process parameters. The size of the T-F curve area reflects the sensitivity of the bolt tightening process to the various process parameters. [ABSTRACT FROM AUTHOR]

The optimization of aerospace structures is a very complex problem, owing to the hundreds of design variables a multidisciplinary optimization may contain, so that multilevel optimization is required. This paper presents recent developments to the optimization software VICONOPT MLO, a multilevel optimization interface between the analysis and design software packages VICONOPT and MSC/NASTRAN. The software developed, VICONOPT MLOP (Multilevel Optimization with Postbuckling) incorporates postbuckling behaviour, allowing individual panels to buckle before the design load is reached, while carrying load at a reduced stiffness. By combining two iterative cycles the first of which (known as the analysis cycle) calculates these reduced postbuckling stiffnesses at an individual panel level in order to converge on an appropriate load distribution at a whole structure or system level and the second of which (known as the design cycle) optimizes individual panels based on this load redistribution to converge on an optimized mass for the whole structure. The paper provides a detailed overview of the functionality of the software and a case study is conducted into the optimization of a composite aircraft wing. The results of the case study show substantial mass savings, proving the software’s capabilities when dealing with such problems. The time taken for this multilevel optimization also demonstrates the efficiency of the software. [ABSTRACT FROM PUBLISHER]

Two new equations are developed for effective electrical conductivity of concentrated particulate composites using a differential scheme along with the solution of an infinitely dilute dispersion of particles in a continuous matrix. The proposed equations are evaluated using 16 sets of experimental data on the electrical conductivity of two-phase particulate systems. The following model developed in the paper describes the experimental data very well: (σ/ σ-m)1/3 (σd - σm)/ (σd - σ)=(1- φ/φm)-αφm) where σ, σm and σd are electrical conductivities of composite, matrix, and dispersed phase (filler) respectively, φ is volume fraction of filler, φm is the maximum packing volume fraction of filler, and α is a constant of the order of unity. In the special case of α = 1 and φm = 1, this model reduces to the well-known Bruggeman equation for the electrical conductivity of two-phase particulate systems. The predictions of the proposed model are significantly different from the predictions of the existing general effective media (GEM) model. [ABSTRACT FROM AUTHOR]

The reflected image on the surface of the fiber-reinforced plastic (FRP) often presents twists and wrinkles. This phenomenon is called print-through phenomenon (PTP) in this investigation and the lines present on the material surface are called print-through lines (PTL). Earlier studies and experimental observations indicate that PTP is related to the non-uniform inner stress in the gel coating layer of the FRP. The non-uniform inner stress is caused by the various shrinkages of the plastic matrix and fibers of the fiber layers during the laminating process. So the main idea to reduce PTP is to reduce or uniform the non-uniform inner stress in the gel coating layer of the FRP. Several methods can be used to reduce PTP and two of them are investigated in this paper. One is removing atmospheric pressure before the plastic matrix of the fiber layers hardens. The other method is inserting a core-Mat layer into the Mat layers during laminating the FRP. Removing atmospheric pressure before the plastic matrix hardens can remove the influence of atmospheric pressure on causing the inner stress of the gel coating layer. Once the inner stress of the gel coating layer is reduced, PTP on the surface of the FRP can be eased off. Inserting a core-Mat layer into the Mat layers will form a buffer zone which can uniform the inner stress in the gel coating layer of the FRP. Therefore, PTP on the surface of the FRP can be eased off. To verify the present contentions, some experiments and qualitative analysis were performed. Both experimental and analysis results show that the PTP on the surface of FRP can be reduced by the present methods. [ABSTRACT FROM AUTHOR]

New models for the elastic properties (Young's and shear moduli, bulk modulus, and Poisson s ratio) of two-phase pore-solid composites are developed using the differential effective medium approach (DEMA). Out of the four models developed in the paper, two models predict the elastic properties to be a function of only one variable, that is, porosity (volume fraction of pores). The remaining two models include an additional parameter, namely the maximum packing volume fraction of pores. The proposed models are evaluated using published experimental data on pore-solid composites, covering a broad range of porosity. [ABSTRACT FROM AUTHOR]

In this paper, a feasible methodology is proposed for the damage-tolerant design of composite sandwich structures and the residual safety evaluation of low-velocity impacted composite sandwich structures. This methodology is based upon the implementation of an event-driven failure criterion called Damage Propagation Criterion. In this criterion, the impact-damaged composite sandwich structure is considered to be unsafe if the damage will propagate to a specified characteristic location near the damage zone under the desired compressive load. The critical far field stress corresponding to the initiation of damage propagation at the specified characteristic location is used as the only characteristic value in this criterion. For a sandwich structure with low-velocity impact damage, this critical far field stress can be determined through either Sandwich Compression After Impact (SCAI) test or numerical analysis by using a modified analytical model or a nonlinear finite element model. Both the experimental and numerical approaches are briefly introduced with examples in this paper. At the end of this paper, the feasible methodology is introduced for the engineering applications in damage-tolerant design of composite sandwich structures and the residual safety evaluation of impact-damaged composite sandwich panels. [ABSTRACT FROM AUTHOR]

This research has been carried on to analyze the capability of a new composite to be effectively used as shielding of gamma radiation. The preparation of a metal-organic composite formed by tungsten and Kraft lignin is presented. Samples have been characterized through X-rays and scanning electron microscopy measurements. The results led to the study of the different phase formations. The microscopic analyzes indicate that two different phases are present in the composite. The absence of oxidation in the process even after the temperature treatment imposed to form the sample has also been noticed. Measurements of the attenuation have been performed to study its ability to absorb gamma radiation. A sample of cobalt 60 (Co-60), for which the peak energies are at 1173 keV and 1332 keV, was used as a source of gamma radiation in the experiment of attenuation. The measured attenuation of gamma radiations when the composite is placed to act as a shield is only 16% smaller than the attenuation obtained for standard pure tungsten. This is a clear indication that the new metal-organic composite is suitable for the fabrication of devices dedicated to shielding radiation, with the advantage of being easier to manipulate. [ABSTRACT FROM AUTHOR]

The extensional flow behavior of a Nylon 6 based engineering plastic filled with short glass fibers was characterized using a Meissner-type uniaxial extensional rheometer. The fiber orientation distributions of the resin samples at various Hencky strains were also determined by X-ray microradiography and image analysis techniques. The uniaxial extensional stress growth function was found to be intimately related to the orientation distribution function of the fibers. [ABSTRACT FROM AUTHOR]

Atheoretical investigation of initial local buckling and post-buckling behavior of composite I-sections is presented. The equilibrium equation for initial buckling is solved both exactly and with an approximate method, namely, Galerkin’s method. In Galerkin’s method, the out-of-plane deflection of each plate element is approximated by a weighted sum of polynomial functions. The post-buckling response is studied as an extension of the approximate analysis with Galerkin’s method where now both equilibrium and compatibility equations must be solved. The bending deflection in the post-buckling regime is assumed to be a magnification of the deflection function used in initial buckling analysis. No mode-shape change is thus allowed in the post-buckling region. A polynomial type of function is also adopted for stress distribution in order to take into account the deviation from uniform in-plane load distribution in the plate elements following the onset of local buckling. The paper provides an efficient and accurate method for predicting the post-buckling behavior of composite structural sections composed of plate elements. Galerkin’s methodwas previously applied to isotropic flat plates only. The present approach is tested against a commercial code, STAGS, with a very good agreement in results and a very large saving in computer time for post-buckling analysis of an I-section. [ABSTRACT FROM PUBLISHER]

Filament wound curved composite parts which are autoclave cured tend to exhibit "spring-in," a permanent deformation due to residual stresses (Stover, 1993). Spring-in is the tendency of a circular part to reduce it's radius of curvature upon radial cutting. The causes of spring-in and the associated residual stresses must be understood to ensure dimensional accuracy and safety of the final cured part. The purpose of this paper is to isolate and quantify the principle causes of spring-in in filament wound unidirectional autoclave cured carbon fiber/epoxy composite hoops.This paper first explores the causes of spring-in as given in the literature: through thickness inhomogeneity (Radford, 1993), part compaction (Meink, 1998), and anisotropy with initial curvature (Kollar, 1992). Next, the development of the residual stress profile through the fabrication and cure process is given along with the governing equations for the spring-in phenomenon. Finally, an experimental procedure is developed to obtain the residual stress profile in a thin composite part. This methodology involves progressive cutting (i.e., stress relief) and associated strain gage monitoring. The strain gage data is then combined with a finite element (FEM) analysis to determine the through-thickness residual stress profile.From the residual stress profile experiments, it was found that the principal cause of spring-in is not material anisotropy as was previously thought. Instead, the principle cause of spring-in was found to be the gradual thermal expansion of the mandrel during cure, which causes a "tension-lag" in the curing part. In addition, the compaction of the part during cure was found to have a nominal contribution to total spring-in. [ABSTRACT FROM PUBLISHER]

This study focuses on failure response and energy absorption of woven ramie epoxy square composite tubes when exposed to the axial quasi-static compression test. Hand lay-up technique was used to prepare the rectangular composite tubes composed of 12 layers of ramie fabric with a thickness of 1.7 mm and 50-, 80-, and 120-mm-long tubes. The measured parameters were specific energy absorption, energy absorption, and peak load. The total energy absorption increased with the increase in the length of the tubes. The failure mode of the tested tubes was examined, and the mid-length and local buckling were considered as the main sources of failure. The woven natural ramie was used in the textiles for years. However, the results of this paper can be significant because of the limited research employing woven ramie as reinforcement for composites. [ABSTRACT FROM AUTHOR]

This paper aims to develop a numerical nonlinear progressive damage model for laminated composite materials considering in-plane and out-of-plane shear stresses in combination with cohesive interface elements to predict the structural response and the failure mechanisms of laminated composite materials. For this purpose, the constitutive models for intralaminar and interlaminar damage modes have been developed as a numerical code by a UMAT subroutine and implemented in commercial finite element software. This model, which is based on the continuum damage mechanics approach, enables to predict the gradual degradation of material properties with five distinct damage parameters for different failure modes; three of these damage factors apply the shear damage contribution as a separate damage mode by a separate damage factor into the model and characterize it by shear damage dissipation energy, and two parameters for fiber and matrix in transverse directions. Also, a series of experiments have been performed to characterize and validate the nonlinear behavior of glass/epoxy laminate. This model is used to predict the behavior and the final strength of open-hole tension specimens. A reasonably good agreement was also achieved between numerical predictions and experimental observations in terms of shapes, orientations and sizes of individual intraply damages induced around the notch and also the final strength of open-hole tension specimen. [ABSTRACT FROM AUTHOR]

This paper reports the dielectric relaxation studies of carbon nanotubes loaded in polyester polymer matrix. The study was carried out in the frequency range between 100 Hz and 1 MHz at constant temperature, T = 300 K. The frequency dependence of the electrical data was treated in the frameworks of the impedance Havriliak-Negami formalism and by using the universal Jonscher power law. The imaginary and real parts of the dielectric permittivity change with concentration of the carbon nanotubes. This work consists in studying the influence of these nanoparticles on the dielectric properties, describing the electrical relaxation and the conduction mechanisms. [ABSTRACT FROM AUTHOR]

This paper presents the effect of stiffeners on the free vibration response of delaminated composite shallow cylindrical shells employing the finite element method. An eight-noded isoparametric shell element based on the first-order shear deformation theory is combined with a three-noded isoparametric curved beam element in the present formulation. The stiffeners follow the nodal lines of the shell wherein the stiffness and mass of the stiffeners are lumped at the corresponding nodal points of the shell elements considering curvature and eccentricity. The generalized dynamic equilibrium equation is derived from Lagrange’s equation of motion, wherein Coriolis effect for moderate rotational speeds is neglected. The multi-point constraint algorithm has been used to model delamination at the desired locations wherein the compatibility of deformation and equilibrium of stress resultants are ensured at the delamination crack front. Numerical results are presented for cantilevered long, intermediate and short cylindrical shells as defined by Aas-Jakobsen’s parameters, and the influence of important parameters like location of delamination, twist angle, rotational speed, number of layers and eccentricity of the stiffeners is studied. The mode shapes for a typical composite un-stiffened and stiffened long cylindrical shell at different rotational speeds and twist angles are also presented. [ABSTRACT FROM AUTHOR]

The paper investigates new composites fully based on wastes of polyethylene terephthalate, rubber, high-density polyethylene, and wood, aiming at multifunctional, environmental-friendly materials, for indoor and outdoor applications. The rubber: polyethylene terephthalate: high-density polyethylene: wood ratio and compression molding temperatures are optimized considering the output mechanical properties, focusing on increasing the waste polyethylene terephthalate content. To investigate the durability in the working conditions, the water-stable composites, with good tensile and compression strengths were exposed to surfactant systems, saline aerosols, and ultraviolet radiations. The results prove that surfactant immersion improves the interfaces and the mechanical properties and a pre-conditioning step involving the dodecyltrimethylammonium bromide surfactant is recommended, prior application. The interfaces and the bulk composites were investigated by X-ray diffraction, Fourier-transform infrared, differential scanning calorimetry, contact angle measurements, scanning electron microscopy, atomic force microscopy, to identify the properties that influence the mechanical behavior and durability. The composites containing 30% of polyethylene terephthalate, obtained at 160℃ and 190℃ have a good combination of mechanical properties and durability that is enhanced by the plasticizing effect of water and surfactants. The compressive strength of the composite processed at 190℃ was 51.2 MPa and the value increased to 58.4 MPa after water immersion. The ultraviolet and saline exposure slightly diminished this effect; however, long time testing (120 h) ended up with values higher than those corresponding to the pristine composite: 55.3 MPa after ultraviolet and 57.1 MPa after saline exposure. [ABSTRACT FROM AUTHOR]

Under environmental conditions, triaxial braided composites exhibit complex behavior and damage mechanisms. This paper investigates the damage mechanisms of these complex composites under varying environmental conditions. Tensile, compressive, and shear specimens of triaxial braided composite material were tested at room, hot (100℃), and hot/wet conditions (60℃/90% relative humidity). The strain field was studied using a digital image correlation system and the effect that the specimens’ edges have on the strain field was quantified. For the tension specimens, the environmental conditions caused reductions in the elastic and failure properties, whereas the compression specimens exhibited degradation exclusively in the failure properties. An increase in temperature rather than humidity was found to be a driving factor for the degradation of the mechanical properties. A non-destructive, flash thermography technique was used to characterize surface/subsurface damage in the specimens. Scanning electron microscopy was conducted to determine the microstructural modes of failure. [ABSTRACT FROM AUTHOR]

Natural fiber has been a focus for environmental and recyclable polymer composite. Liquid composite molding process is an attractive manufacturing technique for natural fiber-reinforced polymer composites with high quality and low cost. Understanding the permeability along different directions of fiber preform is important for liquid composite molding to design and optimize mold and processing parameters. This paper addresses issues of the permeabilities along longitudinal direction of ramie fiber bundles and through-thickness direction of ramie fabric stack. Two simple methods were designed to detect axial and transverse infiltration with assistance of external vacuum pressure in ramie bundles and ramie fabric stack, respectively. Different surface chemical treatments, including flame retardant, silane and alkali treatments, were done on ramie fabric. The effects of fiber content, liquid type and surface treating method on the permeability and capillary pressure were studied. The results show that surface treatment obviously changes the surface morphology and surface energy of ramie fiber. The relationships between defined relative velocities of penetration flow and applied pressure for ramie fiber bundles and fabrics perfectly follow linear relationships, indicating that Darcy’s law is suitable for describing permeation behavior in ramie fibers. Moreover, fiber content and liquid type, including silicone oil and epoxy resin, significantly impact axial permeability and capillary pressure. Surface treatment significantly decreases the permeability along the thickness direction of ramie fabric stack followed by increasing capillary pressure, which are attributed to the changes of treated ramie fibers in surface energy and morphology. Finally, a unique difference in the permeabilities along axial and thickness directions was pointed out. [ABSTRACT FROM AUTHOR]