Investigation of 3D printing strategy on the mechanical performance of coextruded continuous carbon fiber reinforced PETG

Fused filament fabrication (FFF) has been used to create prototypes and functional parts for various applications using plastic filaments. It has also been extended to the use of continuous fibers for reinforcing thermoplastic polymers. This study aims to optimize the deposition design of a coextruded continuous carbon fiber (CCF) composite filament with a polyethylene terephthalate glycol-modified (PETG) filament. The characterizations on the raw materials revealed that the matrix polymer in CCF composite filament had similar physicochemical properties as PETG, and carbon fibers were homogeneously distributed in CCF filament. The effect of raster orientation and shells number on the mechanical properties of non-reinforced and coextruded CCF-reinforced PETG was investigated. The highest mechanical properties were obtained at a raster orientation of 0° for both reinforced and non-reinforced materials. With the increase of raster orientation, Young's modulus and ultimate tensile strength decreased. The presence of shells improved the tensile strength of non-reinforced PETG. For composite samples printed with unreinforced shells, Young's modulus decreased due to decrease in fibers content, and elongation at break and ultimate tensile strength increased. Tomographic observations showed that the mechanical behavior of printed specimens depended on the anisotropy of porosity in printed specimens.     

GF/PP混纤纱及其复合材料性能初探

通过实验,对混纤纱制备热塑性复合材料进行了相关的工艺探索,并对试样进行了测试。结果表明,采用混纤纱法制备的热塑性复合材料制品的综合力学性能比SFT、LFT、GMT均优异,仅次于Twintex。随着玻纤含量的提高,混纤纱的拉伸强度、拉伸模量均明显提高,而弯曲强度和弯曲模量则呈现出先升后降的趋势。试验指出了存在的有关原材料本身和混纤工艺存在的问题,并提出了解决方法和今后的研究方向。     

制备工艺对亚麻增强聚丙烯复合材料拉伸性能的影响

以亚麻纤维为增强体,与聚丙烯（PP）长丝进行丝束级共混,形成PP包覆亚麻的纱线结构,利用机织工艺织成二维机织布,作为复合材料的预制件。采用层合热压方法制备PP／亚麻复合材料板材。通过对板材拉伸性能测试及扫描电镜（SEM）拉伸断口形貌分析,研究了不同纤维体积分数、织造密度及织造组织等因素对复合材料拉伸性能的影响。结果表明,在选取最优热压温度与压力的条件下,纤维体积分数为50％的板材性能最优;经向密度相同时,拉伸性能随着纬向密度的增加而提高;经、纬向密度均相同时,斜纹3／1组织的板材性能最优,纬向最大拉伸强度可达92．42 MPa。     

Influence of the impregnating property on mechanical properties of commingled yarn composites

Three types of glass/nylon 6 intermediate material forms-film stacking, uncommingled yarn, and commingled yarm-were selected study the correlations between the impregnating property and mechanical properties. The size of the glass fiber block to be filled with matrix and the porosity in glass fiber bundles by spearing out the fiber bundle was different in these materials. Unidirectional glass fiber reinforced thermoplastic composites were fabricated by compression molding. The being test was performed by using the three-point loading system, and the fracture behavior and the degree of impregnation were observed to examine the influence of processing conditions on the bending properties, relative to the form of the intermediate material. Bending strength increased, in accordance with the impregnating property, least in the film stacking form, second most in uncommingled yarn, and most in commingled yarn. The impregnating property was affected by the size of fiber blocks and the porosity in fiber bundles, because bending strength was improved by spreading out the fiber bundles. Commingled yarn is an excellent intermediate materials, which has both the fineness of matrix/fiber mixing and large porosity in fiber bundles.     

Comparison of tensile,thermal, and thermo‐mechanical properties of polyester filaments having different cross‐sectional shape

One of the most important morphological features of fibers is their cross‐sectional shape. Nowadays, the circular fiber cross‐section is the most common shape of melt‐spun man‐made fibers. Other shapes are beginning to emerge for a variety of reasons such as performance, comfort, pilling propensity, bulkiness, tactility, processing etc. The filaments' cross‐section can be easily varied by changing the spinneret hole shape. Synthetic fibers that are predominantly spun by the melt spinning method with spinnerets having the noncircular hole geometry are called profiled or noncircular fibers. Modifications of the fiber cross‐section allow designing surface properties in yarn and fabric. However, the effect of profiled fibers on yarn properties has not been well documented yet. In this article, the influence of different filament cross‐section geometry on fiber properties was studied. PET (polyethylene terephthalate) filament yarns having two different cross‐sectional shaped filaments, circular and cruciform, were manufactured by melt spinning. Differences in tensile properties of filament yarn and as well as of individual filament depending on the cross‐sectional type were studied and revealed. More over, thermal and thermomechanical properties of filament yarn of both the cross‐sections were studied and revealed by DSC and TMA method, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical characterization and fractography of glass fiber/polyamide (PA6) composites

The mechanical properties of the glass fiber reinforced Polyamide (PA6) composites made by prepreg tapes and commingled yarns were studied by in‐plane compression, short‐beam shear, and flexural tests. The composites were fabricated with different fiber volume contents (prepregs—47%, 55%, 60%, and commingled—48%, 48%, 49%, respectively) by using vacuum consolidation technique. To evaluate laminate quality in terms of fiber wet‐out at filament level, homogeneity of fiber/matrix distribution, and matrix/fiber bonding standard microscopic methods like optical microscopy and scanning electron microscopy (SEM) were used. Both commingled and prepreg glass fiber/PA6 composites (with V_f ∼ 48%) give mechanical properties such as compression strength (530–570 MPa), inter‐laminar shear strength (70–80 MPa), and transverse strength (80–90 MPa). By increasing small percentage in the fiber content show significant rise in compression strength, slight decrease in the ILSS and transverse strengths, whereas semipreg give very poor properties with the slight increase in fiber content. Overall comparison of mechanical properties indicates commingled glass fiber/PA6 composite shows much better performance compared with prepregs due to uniform distribution of fiber and matrix, better melt‐impregnation while processing, perfect alignment of glass fibers in the composite. This study proves again that the presence of voids and poor interface bonding between matrix/fiber leads to decrease in the mechanical properties. Fractographic characterization of post‐failure surfaces reveals information about the cause and sequence of failure. POLYM. COMPOS., 36:834–853, 2015. © 2014 Society of Plastics Engineers     

混纤技术在纤维增强热塑性塑料加工中的应用

采用增强用纤维与热塑性树脂的纤维混合的方法加工纤维增强热塑性塑料，讨论热塑性树脂的造反及混纤织物类型对增强塑料性能的影响。     

Thermo‐mechanical behavior of stretch‐broken carbon fiber and thermoplastic resin composites during manufacturing

Stretch‐broken fiber reinforcements and thermoplastic resin commingled prepregs are interesting for manufacturing composite parts in aeronautic and automobile industries. With these materials it is possible to produce composite parts with complex geometries, and high curvatures. On the other hand the length of the fibers leads to mechanical properties of the final composite that are close to those of the composite with continuous fibers. This paper analyzes the thermo‐mechanical properties of Stretch Broken Carbon Fiber (SBCF) / PPS and PEEK commingled prepregs during manufacturing. Tensile and in‐plane shear tests at different temperatures are analyzed. The experiments are realized in an isothermal oven. The range of temperature is those of the part during a thermoforming process. The experimental data allow to analyze the differences on the tensile and in‐plane shear behaviors at different temperatures between thermoplastic prepregs with continuous fibers and thermoplastic prepregs with stretch‐broken fibers. Forming simulations show that wrinkling can be avoided with SBCF prepregs while these wrinkles develop during continuous fibers prepreg forming. POLYM. COMPOS., 36:694–703, 2015. © 2014 Society of Plastics Engineers     

Evaluation of fiber surfaces treatment and sizing on the shear and transverse tensile strengths of carbon fiber-reinforced thermoset and thermoplastic matrix composites

The mechanical performance of advanced composite materials depends to a large extent on the adhesion between the fiber and matrix. This is especially true for maximizing the strength of unidirectional composites in off-axis directions. The materials of interest in this study were PAN-based carbon fibers (XA and A4) used in combination with a thermoset (EPON 828 epoxy) and a thermoplastic (liquid crystal poymer) matrix. The effect of surface treatment and sizing were evaluated by measuring the short-beam shear (SBS) and transverse flexural (TF) tensile strengths of unidirectional composites. Results indicated that fiber surface treatment improves the shear and trasverse tensile strengths for both thermosetting and thermoplastic matrix/carbon fiber-reinforced unidirectional composites. A small additional improvement in strengths was observed as the result of sizing treated fibers for the epoxy composites. Scanning electron microscope photomicrographs were used to determine the location of composite failure, relative to the fiber-matrix interface. Finally, the epoxy composites SBS and TF strengths appear to be limited to the maximum transeverse tensile strength of the epoxy matrix, while the thermoplastic composite SBS and TF strengths are limited by the LCP matrix shear and transverse tensile strengths, respectively.     

Development and evaluation of surface treatments to enhance the fiber-matrix adhesion in PAN-based carbon fiber/liquid crystal polymer composites. Part I: Coupling agent and amine surface treatments

Several surface treatments, using both commercially available coupling agents and reagents containing multiple amines, were applied to commingled continuous as-received AS4 carbon reinforcing fiber/liquid crystal polymer (LCP) matrix fibers. Unidirectional composites (normally 60 vol% carbon fiber) were prepared from as-received and treated commingled fibers and characterized. To estimate the effect the effect of the treatments on fiber-matrix adhesion, short beam shear (SBS) tests were conducted, the failure surfaces were examined, and spectroscopic studies wee performed. The mean SBS strength of the as-received unidirectional AS4 carbon fiber/LCP matrix composite system was 49 MPa. The best coupling agent and amine treatments yielded increases in composite shear strength of ∼ 10 to 20%, relative to the as-received AS4/LCP system. For the amine treatments, ESCA and FTIR analyses suggested of both the carbon and LCP fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers (both with coupling agents and amines) showed that strong fiber-matrix adhesion was present. That is, failure occurred in the LCP matrix material.     

二醋酯长丝复合空气变形纱的性能比较

采用5种不同83．3 dtex合纤长丝作芯丝,分别与177．34 dtex二醋酯长丝进行复合空气变形加工, 分析了不同芯丝对变形纱的结构及其性能的影响。结果表明,复合变形纱的强伸性能和沸水收缩率主要由其芯丝决定;5种芯丝中,以PFT FDY作芯丝时,复合空变纱的丝圈稳定性最好,结构膨松性良好、断裂强度较高,断裂伸长率、2 mm高度毛羽数和成纱外观均匀性居中,但沸水收缩率偏大。     

Anisotropy in mechanical and dynamic properties of composites based on carbon fiber filled thermoplastic elastomeric blends of natural rubber and high density polyethylene

The effects of short carbon fibers on static and dynamic properties of thermoplastic elastomeric blends of natural rubber (NR) and high density polyethylene (HDPE) have been studied. Both mechanical and dynamic properties are dependent on fiber concentration. The fiber aspect ratio ranges from 20 to 30. Adhesion between fiber and matrix is evident from the SEM photomicrographs of the failed composites and from variation of relative damping properties. Fiber orientation occurring during processing causes anisotropy in the physical properties. In composites with longitudinally oriented fibers, tensile failure occurs by both fiber pullout and breakage, while in composites with transversely oriented fibers, matrix failure dominates. The incorporation of fibers into the matrix lowers the tan δ_max value, but no change in glass transition temperature is observed.     

Manufacture and thermomechanical characterization of wet filament wound C/C-SiC composites

The paper presents manufacture of C/C-SiC composite materials by wet filament winding of C fibers with a water-based phenolic resin with subsequent curing via autoclave as well as pyrolysis and liquid silicon infiltration (LSI). Almost dense C/C-SiC composite materials with different winding angles ranging from ±15° to ±75° could be obtained with porosities lower than 3% and densities in the range of 2 g/cm³. Thermomechanical characterization via tensile testing at room temperature and at 1300°C revealed higher tensile strength at elevated temperature than at room temperature. Thus, C/C-SiC material obtained by wet filament winding and LSI-processing has excellent high-temperature strength for high-temperature applications. Crack patterns during pyrolysis, microstructure after siliconization, and tensile strength strongly depend on the fiber/matrix interface strength and winding angle. Moreover, calculation tools for composites, such as classical laminate and inverse laminate theory, can be applied for structural evaluation and prediction of mechanical performance of C/C-SiC structures.     

Structural degradation and mechanical fracture of hybrid fabric reinforced composites

This investigation involves the study of accelerated environmental aging in two polymer composite laminates reinforced by hybrid fabrics based on carbon, Kevlar and glass fibers. Composite laminate configurations are defined as a laminate reinforced with E‐glass fiber and Kevlar 49 fiber hybrid fabric (GK) and another laminate reinforced with E‐glass fiber and AS4 carbon fiber hybrid fabric (GC). Both laminates were impregnated with epoxy vinyl ester thermosetting resin (Derakane 470‐300) consisting of four layers. Morphological studies (photo‐oxidation process and structural degradation) of environmental aging were conducted, in addition to comparative studies of the mechanical properties and fracture characteristics under the action of uniaxial tensile and three‐point bending tests in specimens in the original and aged conditions. With respect to uniaxial tensile tests for both laminates, good mechanical performance and little final damage (small loss of properties) was caused by the aging effect. However, for the three‐point bending tests, for both laminates, the influence of aging was slightly higher for all parameters studied. The low structural deterioration in the laminates is attributed to the high performance with the heat of the matrix (Derakane 470‐300) and the characteristics of the hybrid fabric, exhibiting fiber/matrix interface quality. POLYM. ENG. SCI., 56:657–668, 2016. © 2016 Society of Plastics Engineers     

Effects of Carbon Yarn Size on the Mechanical Properties of Plain Woven C/SiC Composites

The effects of yarn size on the mechanical properties of silicon carbide composites reinforced with a plain woven carbon cloth with two sizes of yarns (1 and 3 k) were investigated. The experimental results show that the composite fabricated with 1 k yarns exhibits greater stiffness and strength than the composite fabricated with 3 k yarns. Microstructural observations revealed the existence of matrix microcracks in both the composites under the as-processed condition due to the large difference of thermal expansion between the fibers and the matrix, which are more severe for the composite with 3 k yarns. The fractured surfaces of the composite with 1 k yarns showed extensive fiber pull-out in contrast to the yarn pull-out in the composite with 3 k yarns. The larger interyarn and intrayarn voids due to difficulties of matrix infiltration in the composite with 3 k yarns represent the primary contribution to the diminished mechanical properties. Unequal yarn sizes give rise to different yarn waviness, which may be another source of difference in the mechanical properties of composites.     

Electrical and Mechanical Properties of Thermoplastic Polyurethane and Polytetrafluoroethylene Powder Composites

To determine the possibility of using polytetrafluoroethylene (PTFE) powder as reinforcing filler in the thermoplastic matrix, the thermoplastic polyurethane (TPU) as the matrix and PTFE powder as reinforcing filler were used to prepare a particulate reinforced composite, in order to determine testing data for electrical and mechanical properties of the composites according to the filler loading in respect to TPU polymer matrix. The TPU and PTFE powder composites were prepared by the milling TPU with 2.5, 5, 7.5, and 10 wt% of PTFE powder in a two roll mill and the milled material is compression moulded to make sheets. From the sheets, the test specimens were made and tested for electrical properties—dielectric strength, dielectric constant, surface, and volume resistivity; fire resistance—rate of burning; mechanical properties—tensile strength and elongation, impact strength, hardness; density and melt flow index. The incorporation of PTFE powder has significantly improved the electrical properties—dielectric strength, dielectric constant, surface and volume resistivity; and fire resistance—rate of burning of thermoplastic polyurethane. However, the tensile strength decreased from 24.91 to 14.71 MPa and tensile elongation increased from 620 to 772 percentage.     

Effect of twisting on mechanical properties of GF/PP commingled hybrid yarns and UD‐composites

This study was conducted due to the necessity for improving the processability of commingled yarns during textile processing, in particular dense 3D preform weaving. Open structure of the commingled yarns caused higher production stops. As a possible solution, GF/PP commingled yarns with different twisting levels were produced. Effect of twisting on the mechanical properties of commingled yarns and on their compression molded UD composites are determined. Further tests were executed about yarn/yarn and yarn/metal friction of twisted commingled yarns, which are important properties during textile processing. Theoretical approaches such as a yarn model with linear bar elements and lamina equation with an equivalent angle distortion of over‐delivery proved useful to relate the structural parameters and mechanical properties. As a result, twisting did not significantly affect the modulus of elasticity of UD‐composites, however, the tensile strength of UD‐composites were reduced by further processing even without twisting. Therefore, small twisting levels can be applied on commingled yarns to improve processability of dense preforms without significantly affecting the mechanical performance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication and mechanical response of commingled GF/PET composites

The mechanical properties and the response to mechanical load of continuous glass fiber reinforced polyethylene terephthalate (GF/PET) laminates have been characterized. The laminates were manufactured by compression molding stacks of novel woven and warp knitted fabrics produced from commingled yarns. The laminate quality was examined by means of optical and scanning electron microscopy. Few voids were found and the laminate quality was good. Resin pockets occurred in the woven laminates, originating from the architecture of the woven fabric. The strength of the fiber/matrix interface was poor. Some problems were encountered while manufacturing the laminates. These led to fiber misalignment and consequently resulted in tensile mechanical properties that were slightly lower than expected. Flexural failures all initiated as a result of compression, and it is possible that the compression strength of the matrix material, rather than its tensile strength, might limit the ultimate mechanical performance of the composites. Flexural failures for both materials were very gradual. The warp knitted laminates were stronger and stiffer than the woven laminates. The impact behavior was also investigated; the woven laminates exhibited superior damage tolerance compared with the warp knitted laminates.     

Crystallization and fiber/matrix interaction during the molding of PEEK/carbon composites

The objective of this work was to investigate the effects of molding conditions (molding temperature, residence time at melt temperature, and cooling rate) on the crystallization behavior and the fiber/matrix interaction in PEEK/carbon composites made from both prepreg and commingled forms. In order to investigate the crystallization behavior of the PEEK matrix, the molding process was simulated by differential scanning calorimetric analysis, DSC. The results show that the prepreg and commingled systems do not have the same matrix morphology; prepreg tape was found to be at its maximum of crystallinity, whereas the commingled system was found to be only partially crystalline. The results show that processing must be carried out at a temperature sufficiently high to destroy the previous thermal history of the PEEK matrix; this is an essential requirement to produce efficient fiber/matrix adhesion in the commingled fabric system. Optical microscopic observations also suggest that matrix morphology near the fibers is dependent on the melting conditions; a well-defined transcrystalline structure at the interface is observed only when the melt temperature is sufficiently high. However, the high temperature of molding can easily result in degradation of the PEEK matrix such as chain scission and crosslinking reactions. Thermal degradation of the matrix during processing is found to affect the crystallization behavior of the composites, the fiber/matrix adhesion, and the matrix properties. This effect is more important in the case of a commingled system containing sized carbon fibers because the sizing agent decomposes in the molding temperature range of PEEK/carbon composites. This produces a decrease of the matrix crystallinity and an elimination of the nucleating ability of the carbon fibers. A transition between cohesive and adhesive fracture is observed when the cooling rate increases from 30°C/min to 71°C/min for the composite made from the commingled fabric. This critical cooling rate is found to closely correspond to a change in the mechanism of crystallization of the PEEK matrix.     

The tensile properties of carbon matrices at temperatures up to 2200 °C

Tensile properties of carbon matrices for carbon/carbon composites made via chemical vapor infiltration (CVI) of a fiber preform, were determined from room temperature to 2200 °C. Microcomposite test specimens were used. For this purpose, a carbon coating was deposited on low modulus carbon fibers via chemical vapor deposition based techniques. The mechanical behavior of the carbon matrix was derived from the stress-strain curves obtained with the single filament reinforced microcomposites. It was related to features of nanostructure characterized using X-ray diffractometry. The trends are discussed with respect to those evidenced on carbon fibers in a previous paper.