Impregnation Behavior Research Articles

Resin Impregnation Behavior in Continuous Carbon Fiber Reinforced Thermoplastic Polyimide

Resin Impregnation Behavior in Continuous Carbon Fiber Reinforced Thermoplastic Polyimide

Resin Impregnation Behavior in Plain Woven CFRP laminates based on Thermoplastic Polyimide

Resin Impregnation Behavior in Plain Woven CFRP laminates based on Thermoplastic Polyimide

Modeling and experimental characterization of power-law fluids impregnation behavior in fabric during compression molding

It is proposed that an impregnation model can predict the porosity of composites for power-law fluids impregnation in fabric. The impregnation model takes the material properties and fabric characteristic dimensions into account. In order to verify the model, glass fabric reinforced polypropylene (PP) composites are fabricated by using compression molding procedure. The impregnation model is validated by a series of comprehensive experiments, and the experimental results are perfectly consistent with the impregnation model’s value. The impregnation process is studied respectively through the model and the experiment. The results of it have shown that the impregnation time can indeed be shortened for compression molding procedure by increasing the processing temperature or increasing the applied pressure.

Maximizing the out-of-plane-permeability of preforms manufactured by dry fiber placement

Dry fiber placement (DFP) is a technology which enables outstandingly high mechanical performance of composite parts as preform structures with load-related fiber orientations can be created with minimum of fiber crimp. Furthermore, DFP has high cost-saving potential due to minimum material wastage during production. Recently, the efficiency has been further improved using an online binder application system, allowing the direct usage of untreated rovings instead of pre-designed rovings with binder applied by the manufacturer. Nevertheless, the poor impregnation behavior of DFP-preforms during liquid composite molding processing methods remains a main challenge. Encouraging an out-of-plane impregnation, e.g. by using a vacuum-assisted or compression resin transfer molding process, reduces the flow length within the preform and is a first step toward reducing cycle times. However, further improvements are required in order to apply DFP-preforming methods in serial production.Within this study influences on the out-of-plane permeability of DFP-preforms were investigated. The considered parameters were related to the material (e.g. binder amount) as well as the layup process and subsequent process steps.

Data assimilation through integration of stochastic resin flow simulation with visual observation during vacuum-assisted resin transfer molding: A numerical study

This study investigated data assimilation through integration of visual observation with a stochastic numerical simulation of resin flow during vacuum-assisted resin transfer molding. The data assimilation was performed using the four-dimensional asynchronous ensemble square root filter and a stochastic numerical simulation by means of the Karhunen–Loève expansion of the permeability field. Through numerical experiments of linear flow, it was verified that the estimation accuracy of the resin impregnation behavior improved compared to that when using conventional data assimilation and that the permeability field could be estimated simultaneously, although it is not explicitly related to the observation. We also investigated the applicability of the proposed method to radial-injection VaRTM by varying the model thickness. The proposed method successfully estimated the resin impregnation behavior and permeability field. Additionally, the required condition for the number of ensemble members was clarified.

炭素繊維強化ポリアミド複合材料における樹脂含浸挙動

Micro-braiding technique is an effective method to overcome a problem of resin impregnation to the carbon fiber reinforced thermoplastics. In this study, we investigated the resin impregnation in the textile composite using micro-braiding technique experimentally and with an analysis based on the Darcy's law and continuous equation. The consolidation experiments are conducted on the plain woven fabrics made of micro-braided yarn composed of carbon fibers (3K, 6K and 12K) and thermoplastics fibers (polyamide) under several molding conditions in order to evaluate the impregnation behavior. Sizing agent was eliminated from some specimens in order to evaluate its effect on impregnation behavior. Good correlation was obtained between the experiments and analytical predictions until impregnation ratio reaches 90%. The experiments reveal that carbon fiber tows with lower amount of sizing agent are necessary for higher resin impregnation.

炭素繊維強化ポリカーボネートの成形

In the molding of the carbon fiber reinforced thermoplastic (CFRTP), impregnation of the carbon fiber (CF) bundle is one of the important issues. In this study, we discussed the influence of the melting viscosity of matrix polycarbonate (PC) resin into the CF fabric substrate on the impregnation behavior, and also discussed the influence of the viscosity of the PC and molding time on the formation mechanism of the void. The CF/PC composites were prepared by using the CF plain fabric and PC film using film stacking method by changing the molding temperature and the molding time. According to the photograph of CF/PC surface, the PC resin into the CF bundle flowed in the chink of the CF bundle and crossing point of CF fabrics. The voids were formed by the PC resin impregnated as surrounding the aggregateofCF.Thesizeofvoids becomes smaller by impregnation of the PC resin into inside of the aggregate of CF. Therefore, when the matrix viscosity of PC is low, resin is easy to flow and the size of voids is easy to become smaller.

VaRTMにおける樹脂含浸挙動に及ぼす拡散メディアの影響

Multipoint measurements for resin flow during VaRTM process are carried out by using embedded fiber optic sensors to evaluate the effect of a resin distribution medium which is incorporated on a fiber preform as a surface layer on resin impregnation behavior. By simultaneously infusing epoxy resin into two glass fiber preforms with or without a distribution medium that are separated by a plastic film, resin amount impregnated through in-plane flow and out-of-plane flow via the distribution medium are compared. It has been indicated that resin amount impregnated through the out-of-plane flow via the distribution medium is found to be dominant especially for thinner fiber preform and be constant at each evaluated region of the resin flow. Numerical calculation for resin impregnation during the VaRTM process is also performed using coefficient of permeability both in in-plane and through-the-thickness direction in the fiber preform. The simulated resin amount impregnated through out-of-plane flow via the distribution medium is found to be constant during the impregnation process due to a constant slope angle of flow front, and be comparable with the experimental results.

連続炭素繊維強化熱可塑性ポリイミド複合材料における樹脂含浸挙動

連続炭素繊維強化熱可塑性ポリイミド複合材料における樹脂含浸挙動

Influence of preforming technology on the out-of-plane impregnation behavior of textiles

Various Liquid Composite Molding processes provide out-of-plane impregnation. Thereby, the emerging pressure distribution leads to a hydrodynamic compaction of the fiber structure. A prediction of the behavior of the fiber structure under these conditions is highly complex, due to strong interdependencies between pressure distribution, compaction behavior, and impregnation behavior. In this study possibilities to influence the hydrodynamic behavior of textiles by preforming technology are investigated, by comparing an untreated glass fiber woven textile with sewed, bindered, sheared, and pre-compacted samples of the same material. A novel measurement apparatus, reproducing the conditions during out-of-plane impregnation, is applied for this purpose. It enables out-of-plane permeability determination simultaneous to online compaction monitoring. Sewing accelerates out-of-plane impregnation, while inactivated binder can preserve the available permeability at high injection pressures. The increasing superficial density and the geometrical changes caused by shearing decrease permeability.

An experimental study of the influence of process parameters on the textile reaction to transverse impregnation

When applying a transverse impregnation within a liquid composite molding process, the main goal is to decrease impregnation time by reducing flow path lengths within the textile. However, the pressure drops emerging during impregnation cause hydrodynamic compaction of the textile as well as a heterogenization of the fiber volume content distribution. Within this study a new approach for the description of such transverse impregnation behavior is presented and exemplarily shown for a woven and a noncrimp fabric. The starting point is a novel measurement system allowing an on-line monitoring of flow-induced compaction during permeability measurement. Using the system, the reaction of both textiles to various flow conditions in terms of pressure drop and flow rate was measured and expressed by a set of functions. These allow continuous interpolation and can be used e.g. as direct input for simulations or to validate existing models. For both textiles a severe reduction of the permeability with increasing pressure drop respectively flow rate was measured. Accordingly, it was found that with increasing injection pressure the flow rate can stagnate or even decrease. Knowledge about such behavior is required for process and tooling optimization concerning cycle-time and cost-efficiency. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

317 組物作製と同時加熱によるCFRTPパイプ成形の含浸プロセスに関する研究

317 組物作製と同時加熱によるCFRTPパイプ成形の含浸プロセスに関する研究

307 VaRTMにおける樹脂含浸挙動に及ぼす拡散メディアの影響

VaRTM process impregnates resin to fiber preform using difference in pressure between atmosphere and vacuum, and attracts attention as a method to mold FRP at relatively low cost. However, resin impregnation behavior in the fiber preform is not understood exactly, and the formation of voids during the process is a problem to be avoided. It is said that a distribution medium which is incorporated on the fiber preform as a surface layer has a significant effect on resin impregnation behavior. In this study, multipoint measurements for resin flow during VaRTM process are carried out by using embedded fibre optic sensors. By simultaneously infusing epoxy resin into two glass fibre preforms with or without a distribution medium that are separated by a plastic film, resin amount impregnated through in-plane flow and out-of-plane flow via the distribution medium are compared. It has been found that resin amount impregnated through the out-of-plane flow via the distribution medium is found to be dominant, especially for thinner fiber preform. In addition, numerical calculation for resin impregnation during the VaRTM process was also carried out. The simulated resin amount impregnated via the distribution medium agreed well with the experimental results.

Effect of preceramic and Zr coating on impregnation behaviors of SiC ceramic composite

SiC fiber-reinforced ceramic composites were fabricated using a polymer impregnation and pyrolysis process. To develop the low temperature process, the pyrolysis was conducted at 600 °C in air. Both a microstructural observation and a mechanical test were utilized for the evaluation of the impregnation. For the impregnation, two kinds of polycarbosilane having a different degree of cross-linking were used. The level of cross-linking affected the ceramic yield of the composites. The cross-linking under oxygen containing atmosphere resulted in a dense matrix and high density of filling. However, tight bonding between the matrix and fibers in the fully dense composite samples, which was obtained using a cross-linking agent of divinylbenzene, turned out to be deteriorative on the mechanical properties. The physical isolation of fibers from matrix phase in the composites was very important to attain a mechanical ductility. The brittle fracture was alleviated by introducing an interphase coating with metallic Zr. The combination of forming the dense matrix and interphase coating should be a necessary condition for the SiCf/SiC fiber-reinforce composite, and it is practicable by controlling the process parameters.

Effects of impregnation and heat treatment on the physical and mechanical properties of Scots pine (Pinus sylvestris) wood

Wood modification, of which thermal modification is one of the best-known methods, offers possible improvement in wood properties without imposing undue strain on the environment. This study investigates improvement of the properties of heat-treated solid wood. Scots pine (Pinus sylvestris) was modified in two stages: impregnation with modifiers followed by heat treatment at different temperatures. The impregnation was done with water glass, melamine, silicone, and tall oil. The heat treatment was performed at the temperatures of 180°C and 212°C for three hours. The modified samples were analyzed using performance indicators and scanning electron microscope micrographs. The mechanical and physical properties were determined with water absorption, swelling, bending strength, and impact strength tests. All the modifiers penetrated better into sapwood than hardwood; however, there were significant differences in the impregnation behavior of the modifiers. As regards the effect of heat treatment, generally the moisture properties were improved and mechanical strengths impaired with increasing treatment temperature. In contrast to previous studies, the bending strength increased after melamine impregnation and mild heat treatment. It is concluded that the properties of impregnated wood can be enhanced by moderate heat treatment.

Study on high-speed RTM to reduce the impregnation time of carbon/epoxy composites

The resin transfer molding (RTM) process is widely used to fabricate carbon fiber reinforced composite structures. However, conventional RTM processes are limited with regard to producing larger structures due to impregnation time significantly increasing in proportion to the surface area of products. In this study, composite plate structures were fabricated using a new high-speed RTM process to reduce impregnation time. The key idea of this method is to change the resin flow direction from in-plane to through-thickness for the preform. Computational fluid dynamics (CFD) simulation was introduced to investigate the impregnation state of preform with respect to the number and size of vacuum gates. Impregnation tests, under conditions similar to those in the CFD simulation, were carried out, and the impregnation behaviors of the resin were compared with the simulation results. Finally, an optimization process was carried out to find the number of vacuum gates and permeability ratio that result in the minimum impregnation time.

Experimental and numerical characterization of resin impregnation behavior in textile composites fabricated with micro-braiding technique

Experimental and numerical characterization of resin impregnation behavior in textile composites fabricated with micro-braiding technique

Impregnation and Characterization of High Performance Extraction Columns for Separation of Metal Ions

Impregnation behaviors of reverse-phase silica materials and C18-silica HPLC columns were studied using di-(2-ethylhexyl)phosphoric acid (HDEHP) as a model extractant. Initially, the adsorption efficiency of the ligand on different types of bulk particles was investigated using various concentration of HDEHP in different composition of methanol/water mixtures based on a batch technique. Subsequently, impregnation of HPLC columns was performed using the dynamic flow-through technique. The experimental data fitted well to the Langmuir model and the adsorption isotherms from the flow-through experiment were used to prepare extraction columns of different ligand densities. Finally, the impregnated columns were characterized and validated through HPLC separation of the lanthanides.

Tensile and impregnation behavior of unidirectional hemp/paper/epoxy and flax/paper/epoxy composites

Natural continuous bast fibres (hemp, flax, etc.) are gaining popularity in composite materials because they can advantageously replace glass fibres. It is found that intrinsic properties of unidirectional (UD) composites are almost equivalent to those of unidirectional glass fibre composites. Unfortunately it is difficult to get repeatable results because of the inherent variability in the properties of bast fibres compared to glass fibres. Their quality is largely affected by the weather conditions, the extraction location along the plant and the techniques used to extract them (retting, bleaching, etc.). In this work, unidirectional hemp/paper/epoxy and flax/paper/epoxy composites are manufactured by adding one or two sheets of paper at the surface of a unidirectional layer of hemp or flax fibres before molding. The composites are tested under tensile loads and the results compared with those obtained for UD composites made without paper. The results show a significant increase in strength and modulus repeatability when the paper layer is present. A significant increase in strength and modulus was also obtained compared to the base epoxy properties. The resin permeability of the flax–paper reinforcement has also been evaluated and compared to that of a standard glass fabric. Globally, the results suggest that adding thin sheets of paper at the surface of reinforcement layers stabilizes and increases the composite strength but slightly reduces the Young’s modulus. However the permeability of the flax–paper reinforcement was much lower than that of the glass fabric. Modifications to the paper architecture will be required to improve this aspect.

Analytical prediction of resin impregnation behavior during processing of unidirectional fiber reinforced thermoplastic composites considering pressure fluctuation

In order to fabricate composite components more rapidly, a micro-braiding technique has been proposed as fabrication of intermediate material for continuous fiber reinforced thermoplastic composites. In the present study, a simple model considering pressure fluctuation during compression molding is proposed based on the Darcy’s law and the continuity equation to predict resin impregnation process using micro-braided yarns. In order to measure pressure fluctuation, a mold die including a channel from the cavity to a pressure gauge was fabricated. To confirm validity of the model, carbon fiber reinforced polypropylene composites were molded under various molding conditions. Once molding pressure was applied, pressure on the molding pieces rapidly increased and gradually decreased to equilibrium with time. Analytical results well-predict resin impregnation during molding and the effectiveness of the model proposed was confirmed.