Carbon fiber‐reinforced gelatin composites. I. Preparation and mechanical properties

Composites were made from carbon fibers and gelatin using a solvent‐casting or solution‐impregnation technique. Relationships between the fiber volume fraction (Vf), glycerol (plasticizer) content, gelatin content, fiber form, and mechanical properties (tensile strength and modulus, elongation at break, and shear strength) of the composites were investigated. In long carbon fiber gelatin composite (C_L/Gel), tensile strength, modulus, and shear strength increased steadily with the Vf. In the case of a short carbon fiber gelatin composite (C_S/Gel), an initial improvement in tensile strength and modulus was followed by a reduction, whereas the shear strength improved with the Vf and then reached a constant value. The elongation decreased with the Vf for both composites. It is shown that C_L/Gel had higher values of strength, modulus, and elongation than did C_S/Gel at any Vf level. The effects of glycerol and gelatin contents on the mechanical properties of the composites were found to be much less significant as compared to the Vf. According to scanning electron microscopic observation of the fracture surfaces, the fibers were uniformly distributed in the gelatin matrix, but the interfacial adhesion between the gelatin matrix and the carbon fibers was not very good for both composites. Fiber surface modification would be necessary to further improve the mechanical properties of the two composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 987–993, 2000     

Comparison of mechanical performance and fracture behavior of gelatin composites reinforced with carbon fibers of different fiber architectures

Gelatin‐based composites reinforced, respectively, with continuous carbon fibers, short carbon fibers, plain woven carbon fibers, and carbon fiber felt were investigated. Tensile and shear strengths, and their changes with fiber volume fraction (V_f) of these four composites were compared. It was demonstrated that at all fiber levels, the composite containing continuous carbon fibers showed the largest strength, while the composite reinforced with carbon fiber felt exhibited the lowest strength of the four composites. The above results were analyzed by comparing the fracture surfaces of the four composites. SEM confirmed the great differences in fracture surfaces for composites of different fiber architectures. The presence of a large number of pores in the C_F/Gel composite was responsible for its lowest strength, and cracks within fiber tows caused the lower strength of the C_W/Gel composite when compared to its C_L/Gel counterpart. It was suggested that fiber architecture exerted a great effect on composite performance and the effect was dependent on the nature of the matrix material.     

Effect of preform and carbon matrix on bending strength of Cf/Cu/C composites

Aiming to obtain composites with appropriate mechanical properties for pantograph sliders, copper mesh modified carbon/carbon (C_f/Cu/C) composites were prepared by chemical vapor infiltration (CVI) in C₃H₆ +?N₂ atmosphere and impregnation-carbonization (I-C) with furan resin. In this paper, C_f/Cu/C composites with two kinds of preforms and carbon matrixes were obtained. The effect of preforms and carbon matrixes on bending strength was investigated. The results indicated that the bending strength of carbon fiber/copper mesh reinforced pyrolytic carbon matrix composites was about 181.39–195.43?MPa, while that reinforced resin carbon matrix composites had the worst bending strength around 54.45–57.04?MPa, in terms of the same preform. The bending strength of C_f/Cu/C composites in the parallel orientation and vertical orientation were also similar. As for C_f/Cu/C composites with the same carbon matrix, the bending strength of C_f/Cu/C composites with non-woven fiber/fiber web/copper mesh type preform was higher than that with fiber web/copper mesh type preform. However, the bending strength of carbon fiber/copper mesh reinforced resin carbon matrix composites showed the opposite trend, and its reasons were analyzed and discussed taking advantage of the fracture mechanisms.     

Mechanical property and microstructure evolutions of Cf/SiOC composites with increasing annealing temperature in reduced pressure environment

Three-dimensional (3D) carbon fiber reinforced silicon oxycarbide (C_f/SiOC) composites were fabricated through precursor impregnation and pyrolysis process using siloxane resin as precursor. These composites were further annealed at various temperatures to follow their mechanical properties and microstructure evolutions in reduced pressure environment. The decrease in strength of those composites could be attributed mainly to the decomposition of matrixes. When the annealing temperature increased from 1000 to 1250 °C, the mechanical properties of composites did not change too much, despite the matrixes underwent a redistribution of Si-O bonds and Si-C bonds. At temperature above 1300 °C, due to the weight loss and volume shrinkage of matrixes caused by carbothermal reduction, both the flexural strength and elastic modulus of C_f/SiOC composites decreased rapidly.     

Interfacial adhesion in sisal fiber/SBR composites: an investigation by the restricted equilibrium swelling technique

Short sisal fiber-reinforced styrene butadiene rubber (SBR) composites were prepared and characterized by the restricted solvent swelling technique. The solvent swelling characteristics of SBR composites containing untreated and bonding agent-added mixes were investigated in a series of aromatic solvents, such as benzene, toluene, and xylene. The diffusion experiments were conducted by the sorption gravimetric method. The adhesion between the rubber and short sisal fibers was evaluated from the restricted equilibrium swelling measurements. The anisotropy of swelling of the composite was confirmed by this study. The effect of fiber orientation in controlling the anisotropy of restricted swelling was also demonstrated. As the fiber content increased, the solvent uptake decreased, due to the increased hindrance and good fiber-rubber interactions. Bonding agent-added mixes showed enhanced restriction to swelling, due to the strong interfacial adhesion. The bonding system containing hexa-resorcinol in the mix produces an in-situ resin, which binds the fiber and the rubber matrix firmly. In addition, as the penetrant size increases from benzene to xylene, the uptake decreases. The swelling index values of the composites support this observation. Due to the improved adhesion between the short sisal fiber and SBR, the ratio of the volume fraction of rubber in the dry composite sample to the swollen sample (V _T) decreases. The extent of fiber orientation of the composites was also analysed from the restricted swelling method. SEM studies of the composite revealed the orientation of short fibers. The sorption data support the Fickian diffusion trend, which is typical in the case of cross-linked rubbers.     

Anisotropic tribological behavior of LSI based 2.5D needle-punched carbon fiber reinforced Cf/C–SiC composites

C_f/C–SiC composites were fabricated via liquid silicon infiltration with 2.5D needle-punched carbon fiber reinforced C_f/C composites. The effect of surface topography and carbon content of the C_f/C–SiC composites on the tribological properties was researched by the ball-on-disk reciprocating tribometer. The results indicate that different fiber layers and cross-section of the composites have various surface topography and show significant differences in the friction and wear properties. By the wear morphology and model analyses, the reason for the tribological anisotropy of the composites is that the distribution of carbon and SiC phases in the composites are inhomogeneous caused by the difference of the carbon fiber orientation and the relative content in each layer. Moreover, the wear rate of the short-cut fiber web layer was the lowest and there is an obvious linear decrease in coefficient of friction with increase of carbon content. The present work explains why the tribological properties of the composites are inconsistent and provides a way to adjust the friction properties of composite materials by optimizing the friction surface.     

Three‐dimensionally braided carbon fiber–epoxy composites,a new type of materials for osteosynthesis devices. II. Influence of fiber surface treatment

Interfacial adhesion between carbon fiber and epoxy resin plays an important role in determining performance of carbon–epoxy composites. The objective of this research is to determine the effect of fiber surface treatment (oxidization in air) on the mechanical properties (flexural strength and modulus, shear and impact strengths) of three‐dimensionally (3D) braided carbon‐fiber‐reinforced epoxy (C_3D/EP) composites. Carbon fibers were air‐treated under various conditions to improve fiber–matrix adhesion. It is found that excessive oxidation will cause formation of micropits. These micropits are preferably formed in crevices of fiber surfaces. The micropits formed on fiber surfaces produce strengthened fiber–matrix bond, but cause great loss of fiber strength and is probably harmful to the overall performance of the corresponding composites. A trade‐off between the fiber–matrix bond and fiber strength loss should be considered. The effectiveness of fiber surface treatment on performance improvement of the C_3D/EP composites was compared with that of the unidirectional carbon fiber–epoxy composites. In addition, the effects of fiber volume fraction (V_f) and braiding angle on relative performance improvements were determined. Results reveal obvious effects of V_f and braiding angle. A mechanism was proposed to explain the experimental phenomena. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1040–1046, 2002     

A novel vibration-assisted slurry impregnation to fabricate Cf/ZrB2-SiC composite with enhanced mechanical properties

The three dimensional needle-punched carbon fiber reinforced ZrB₂-SiC composite (C_f/ZrB₂-SiC) with highly uniform distribution was fabricated successfully via a novel vibration-assisted slurry impregnation and low-temperature (1450 °C) hot pressing technique using nanosized ZrB₂ powders. The carbon fiber/ceramic matrix interfaces were clear without obvious reaction products detected by the high resolution transmission electron microscopy (HR-TEM), indicating the degradation of carbon fiber was effectively inhibited. The C_f/ZrB₂-SiC composite exhibited a typical non-brittle fracture feature with a high work of fracture of 1104 J/m², which was approximately twice that of composite fabricated only by slurry impregnation and hot pressing. The enhancement in work of fracture was attributed to multiple toughening mechanisms of continuous carbon fibers such as extensive fiber bridging and pull-out accompanied by obvious crack deflection and branching. This work provides a valuable potential of preparing continuous carbon fiber reinforced ceramic composites with uniform component distribution and enhanced mechanical properties.     

Direct ink writing of chopped carbon fibers reinforced polymer-derived SiC composites with low shrinkage and high strength

The chopped carbon fiber reinforced SiC (C_f/SiC) composite has been regarded as one of the excellent high-temperature structural materials for applications in aerospace and military fields. This paper presented a novel printing strategy using direct ink writing (DIW) of chopped fibers reinforced polymer-derived ceramics (PDCs) with polymer infiltration and pyrolysis (PIP) process for the fabrication of C_f/SiC composites with high strength and low shrinkage. Five types of PDCs printing inks with different C_f contents were prepared, their rheological properties and alignment of carbon fiber in the printing filament were studied. The 3D scaffold structures and bending test samples of C_f/SiC composites were fabricated with different C_f contents. The results found that the C_f/SiC composite with 30 wt% C_f content has high bending strength (～ 7.09 MPa) and negligible linear shrinkage (～ 0.48%). After the PIP process, the defects on the C_f/SiC composite structures were sufficiently filled, and the bending strength of C_f/SiC composite can reach up to about 100 MPa, which was about 30 times greater than that of the pure SiC matrix without C_f. This work demonstrated that the printed C_f/SiC composites by using this method is beneficial to the development of the precision and complex high-temperature structural members.     

Fabrication and characterization of carbon fiber reinforced SiC ceramic matrix composites based on 3D printing technology

A novel method has been developed to fabricate carbon fiber reinforced SiC (C_f/SiC) composites by combining 3D printing and liquid silicon infiltration process. Green parts are firstly fabricated through 3D printing from a starting phenolic resin coated carbon fiber composite powder; then the green parts are subjected to vacuum resin infiltration and pyrolysis successively to generate carbon fiber/carbon (C_f/C) preforms; finally, the C_f/C preforms are infiltrated with liquid silicon to obtain C_f/SiC composites. The 3D printing processing parameters show significant effects on the physical properties of the green parts and also the resultant C_f/C preforms, consequently greatly affecting the microstructures and mechanical performances of the final C_f/SiC composites. The overall linear shrinkage of the C_f/SiC composites is less than 3%, and the maximum density, flexural strength and fracture toughness are 2.83?±?0.03?g/cm³, 249?±?17.0?MPa and 3.48?±?0.24?MPa m^1/2, respectively. It demonstrates the capability of making near net-shape C_f/SiC composite parts with complex structures.     

Effect of pyrolytic carbon coating on the microstructure and fracture behavior of the Cf/ZrB2-SiC composite

The high sintering temperature and interface interaction seriously degraded the toughening effects of continuous carbon fiber in ZrB₂-SiC ceramic. The pyrolytic carbon coated carbon fiber reinforced ZrB₂-SiC composite (C_f-PyC/ZrB₂-SiC) with desirable properties was successfully achieved via brushing nano ZrB₂-SiC slurry followed by spark plasma sintering at relatively low sintering temperature. The fabricated C_f-PyC/ZrB₂-SiC composite presented a non-brittle fracture feature and a remarkable enhancement in comparison with the ZrB₂-SiC composite reinforced by the as-received carbon fiber (C_f-AS/ZrB₂-SiC). The fracture toughness and critical crack size were increased from 5.97?±?0.18–7.66?±?0.24?MPa?m^1/2 and from 91.6 to 164.5?µm, respectively. A high work of fracture of 1915?J/m² for C_f-PyC/ZrB₂-SiC composite was achieved, almost four times higher than that of the C_f-AS/ZrB₂-SiC composite (463?J/m²). Multiple toughening mechanisms contributed to such enhancement, such as crack deflection, fiber bridging, fiber pull-out and crack branching. This work provides a feasible approach to fabricate high-performance fiber reinforced ceramic composites having a high work of fracture.     

Three‐dimensionally braided carbon fiber–epoxy composites,a new type of material for osteosynthesis devices. I. Mechanical properties and moisture absorption behavior

In recent years, three‐dimensionally (3D) braided composites have attracted a great deal of attention because of their high‐impact damage tolerance and fatigue life, superior fracture toughness, and so forth, and have been used in aeronautics, military, and transportation. These advantages make them strong candidates for osteosynthesis devices. In this study, 3D braided carbon fiber–epoxy (C_3D/EP) composites were produced via a simple vacuum impregnation technique. The load‐deflection curve, mechanical properties, and influence of fiber volume fraction, braiding angle, and axial reinforcing fibers were examined to determine their suitability for internal fixation devices. It is found that the C_3D/EP composites have excellent toughness and do not show brittleness when fractured because of their relatively high void content. The flexural, shear, and impact strengths of the C_3D/EP composites are excellent. It was shown that a C_3D/EP composite with a stiffness similar to load‐bearing bones can be made while maintaining enough strength. It is concluded that a relatively higher void content and braiding angle is more suitable for the C_3D/EP composites from the viewpoint of requirements of fracture fixation materials. The moisture absorption behavior and changes in mechanical properties caused by moisture uptake were evaluated. Results show that absorbed moisture slightly decreases mechanical properties of the C_3D/EP composites. Contrary to the unreinforced epoxy, the moisture absorption behavior of the C_3D/EP composites cannot be described with Fick's law of diffusion, probably because of the presence of voids and/or 3D fiber structure. The exact mechanisms should be proposed in further investigations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1031–1039, 2002     

Interphase degradation of three‐dimensional Cf/SiC–ZrC–ZrB2 composites fabricated via reactive melt infiltration

Layer‐structured interphase, existing between carbon fiber and ultrahigh‐temperature ceramics (UHTCs) matrix, is an indispensable component for carbon fiber reinforced UHTCs matrix composites (C_f/UHTCs). For C_f/UHTCs fabricated by reactive melt infiltration (RMI), the interphase inevitably suffers degradation due to the interaction with the reactive melt. Here, C_f/SiC–ZrC–ZrB₂ composite was fabricated by reactive infiltration of ZrSi₂ melt into sol‐gel prepared C_f/B₄C–C preform. (PyC–SiC)₂ interphase was deposited on the fiber to investigate the degradation mechanism under ZrSi₂ melt. It was revealed that the degraded interphase exhibited typical features of Zr aggregation and SiC residuals. Moreover, the Zr species diffused across the interphase and formed nanosized ZrC phase inside the fiber. A hybrid mechanisms of chemical reaction and physical melting were proposed to reveal the degradation mechanism according to characterization results and heat conduction calculations. Based on the degradation mechanism, a potential solution to mitigate interphase degradation is also put forward.     

Characterization of partially densified 3D Cf/SiC composites by using mercury intrusion porosimetry and nitrogen sorption

The microstructure of partially densified three-dimensional carbon fiber fabrics reinforced silicon carbide (C_f/SiC) composites are characterized by both mercury intrusion porosimetry (MIP) and isothermal nitrogen sorption (INS). By comparison, MIP is preferable to the characterization for its wide effective probing ranges. Based upon multiple measurements, in the C_f/SiC composite, exists a complicated three-dimensional porous network formed by the interconnecting pores and necks with various sizes, diverse shapes and rough surfaces.     

Flammability and thermomechanical properties of dianhydride‐modified polybenzoxazine composites reinforced with carbon fiber

Composites based on carbon fiber (CF) and benzoxazine (BA‐a) modified with PMDA were investigated. The flammability of the carbon fiber composites was examined by limiting oxygen index (LOI) and UL‐94 vertical tests. The LOI values increased from 26.0 for the CF/poly(BA‐a) composite to 49.5 for the CF‐reinforced BA‐a/PMDA composites as thin as 1.0 mm and the CF‐reinforced BA‐a/PMDA composites were also achieved the maximum V‐0 fire resistant classification. Moreover, the incorporation of the PMDA into poly(BA‐a) matrix significantly enhanced the T_g and the storage modulus (E') values of the CF‐reinforced BA‐a/PMDA composites rather than those of the CF/poly(BA‐a). The T_g values and storage moduli of the obtained CF‐reinforced BA‐a/PMDA composites were found to have relatively high value up to 237°C and 46 GPa, respectively. The CF‐reinforced BA‐a/PMDA composites exhibited relatively high degradation temperature up to 498°C and substantial enhancement in char yield with a value of up to 82%, which are somewhat higher compared to those of the CF/poly(BA‐a) composite, i.e., 405°C and 75.7%, respectively. Therefore, due to the improvement in flame retardant, mechanical and thermal properties, the obtained CF‐reinforced BA‐a/PMDA composites exhibited high potential applications in advanced composite materials that required mechanical integrity and self‐extinguishing property. POLYM. COMPOS., 34:2067–2075, 2013. © 2013 Society of Plastics Engineers     

Characterization and mechanical properties of Cf/ZrB2-SiC composites fabricated by a hybrid technique based on slurry impregnation,polymer infiltration and pyrolysis and low-temperature hot pressing

The continuous carbon fiber reinforced ZrB₂-SiC composite was fabricated successfully via a hybrid technique based on nano ceramic slurry impregnation, polymer infiltration and pyrolysis and low-temperature hot pressing. The C_f/ZrB₂-SiC composites exhibited non-brittle fracture modes and the chemical interaction at the fiber/matrix interfaces was effectively inhibited owing to the low sintering temperature. The S2-C_f/ZrB₂-SiC composite presented the highest mechanical properties with fracture toughness of 4.47?±?0.15?MPa?m^1/2 and the work of fracture of 877?J/m², which was attributed to the multiple length-scale toughening mechanisms including the macroscopic toughening mechanisms of crack deflection and crack branching, the micro toughening mechanisms of fiber bridging and fiber pull-out. This work presented a novel and effective method to fabricate high-performance continuous carbon fiber reinforced ceramic matrix composites.     

Influences of clearance angle and point angle on drilling performance of 2D Cf/SiC composites using polycrystalline diamond tools

C_f/SiC composite (carbon fiber reinforced silicon carbide ceramic matrix composites) is a kind of advanced composite material constituted by SiC as matrix and carbon fiber as reinforcing phase. C_f/SiC composites are being extensively used in the modern aerospace industry owing to their excellent physical and mechanical properties. The current work aims to investigate influences of clearance angle and point angle on drilling performance of 2D C_f/SiC composites using PCD (polycrystalline diamond) tools in terms of thrust force, drilling torque, hole surface quality, and material removal mechanism. PCD drill bits with different point angles and clearance angles were used in the experiment. The obtained results indicate that the 150° point angle is beneficial to improve the hole surface quality, and larger clearance angle is helpful to reduce the damage of exits. Additionally, the variation of clearance angle has little effect on the roughness of the machined surface. During the drilling process, the dominated material removal mechanisms are matrix removal, fiber breakage, and matrix-fiber debonding. The brittle fracture mode of carbon fibers, which directly affects surface roughness, can be divided into micro-brittle fractures in carbon fiber and macro-brittle fractures. Besides, the damage identification method of hole entrance and exit based on image processing technology is helping to improve the efficiency of machining quality evaluation.     

Sugar palm fiber/polyester nanocomposites: Influence of adding nanoclay fillers on thermal,dynamic mechanical,and physical properties

In this research, nanoclay used as filler in sugar palm‐reinforced composites was investigated by the physical, thermal, and dynamic mechanical properties. Various concentrations of nanoclay were used to fabricate composites by using hand lay‐up technique, followed by hot compression molding with naturally woven sugar palm fiber‐reinforced in polyester matrix. Among various weight concentrations such as 1–5% of nanoclay, it was found that 2% nanoclay‐filled composite (NC) demonstrated the best balance of thermomechanical properties and significantly enhanced the composite. DMA demonstrated that 2% nanoclay content resulted in improved viscoelastic behavior and higher glass transition temperature (T_g) of the composites. TGA also showed improvement in properties, whereas 3% nanoclay‐filled composite showed superior onset temperature, and 5% nanoclay‐filled composite exhibited highest remaining residue. The nanoclay filler was very effective to fill the porous structure and maintain the thickness stability. The thickness swelling was reduced with increasing amount of nanoclay in composites. Overall, the addition of nano clay improved thermal and physical properties of sugar palm‐reinforced polyester composite. J. VINYL ADDIT. TECHNOL., 26:236–243, 2020. © 2019 Society of Plastics Engineers     

Water absorption behavior of PALF/GF hybrid polyester composites

The water absorption characteristics of pineapple leaf fiber (PALF)/glass fiber (GF) hybrid polyester(PER) composites, and chemically modified PALF/polyester composites were evaluated by immersion in distilled water at 28, 60, and 90°C. The diffusion properties of the intimately mixed (IM) and the layered hybrid composite GPG (Glass skin and PALF core) of different PALF/GF ratio at the three temperatures were compared in order to identify the environmental ageing mechanism at different temperatures. The effect of temperature on the kinetics and thermodynamics of diffusion were also examined. The water uptake of both IM and GPG hybrid composites was decreased with increase in glass fiber content; the lowest water uptake was observed for 0.46 V_f GF hybrid composite. Among the chemically modified composites, vinyl tri 2‐methoxy ethoxy silane treated composites showed the lowest water uptake. Finally, parameters like diffusion, sorption, and permeability coefficients were determined. It was observed that equilibrium water uptake is dependent on the nature of the composite and temperature. Experimental results were also compared with theoretical predictions. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Interfacial microstructure and strengthening mechanisms of Cf/Mg composite with double-layer interface

In order to overcome the interfacial incompatibility of carbon fiber reinforced magnesium matrix (C_f/Mg) composites, a double-layer interface (ZrO₂–MgO) is designed in this work. Carbon fiber was modified with ZrO₂ coating by sol-gel process. Microstructural examination reveals that MgO layer forms on the surface of ZrO₂ coating by ZrO₂ reacting with Mg during the composite fabrication. Such double-layer interface could inhibit Al₄C₃ and hence prevent fiber damage. Meanwhile, the wettability was improved for the reaction between ZrO₂ and Mg. Thus the tensile strength of ZrO₂-C_f/AZ91D composite was 68.0% higher than that of the unmodified one. Due to the fiber bundle pull-out, debonding and crack deflection, the toughness of C_f/Mg composite with double-layer interface is increased simultaneously.