Film Stacking Technique Research Articles

Preparation and characterization of silk hybridizing carbon fiber/polybutylene succinate composite

AbstractCarbon fiber‐reinforced composites (CFRPs) offer numerous benefits due to their exceptional strength and modulus, making them extensively utilized in various applications. However, the disadvantage of poor impact resistance also limits their application in some aspects. In this study, silk fabric is used to hybridize CFRPs, and the silk/carbon fiber‐reinforced polybutylene succinate (PBS) composites were fabricated by combining the film stacking technique with the hot‐pressing method. The mechanical, thermal, and thermodynamic properties of the composites were assessed using various techniques, including tensile testing, scanning electron microscope, flexural testing, Charpy impact test, low‐velocity impact test, differential scanning calorimetry, and dynamic mechanical thermal analysis, and the optimal preparation process conditions (140°C/15 min) for the composites were obtained. Additionally, the mechanical properties of silk fiber/PBS, carbon fiber/PBS, and hybrid composite materials are comprehensively compared and evaluated. This work indicates that the synergistic toughening of silk and PBS significantly improves the impact resistance of CFRPs, and the impact strength of sample 5 (140°C/15 min) (54.97 kJ/m2) is higher than many reported values for CFRPs.Highlights High strength, high modulus carbon fiber, and high toughness silk were rarely combined as reinforcing phases for PBS composites. A hybrid composite material with a balanced combination of stiffness, strength, and toughness was prepared. Compared with similar studies, it was found that the hybrid composite prepared by this work exhibited relatively balanced mechanical properties, especially, its impact strength higher than many reported values.

Fabrication of continuous carbon fiber reinforced polyamide 6 composites by means of self‐resistance electric heating

AbstractIn the conventional process of thermoplastic composites, a heating stage from the external heat source usually consumes a large amount of energy. To solve this problem, self‐resistance electric (SRE) heating of carbon fiber‐reinforcement was introduced to form a continuous carbon fiber reinforced polyamide 6 (CF/PA 6) composite based on film stacking technique in this paper. The temperature distribution was first measured to verify the temperature uniformity for SRE heating process. X‐ray photoelectron spectroscopy (XPS) was used to assess effects on the chemical properties of carbon fibers from SRE heating and conventional convective heating. To evaluate forming quality by SRE heating, the physical properties, crystallinity, and mechanical properties of CF/PA 6 composites were measured. The results show that the forming time and energy consumption of SRE heating process are significantly reduced compared with that of the traditional heating process because of fast heating/cooling rate. While fast heating/cooling rate of SRE heating process leads to a higher void content, which finally results in a slightly lower flexural strength and impact properties of composite laminates. It is clear that SRE heating technique is one of the energy‐ and cost‐effective ways to fabricate continuous carbon fiber reinforced thermoplastic composites although the forming quality is still improved in future investigation.

Processing of PAEK-graphite fabric composites – Pros and cons of film technique over powder sprinkling technique

Fabric-(BD-bi-directionally) reinforced high performance polymer composites are well-known for their exceptional mechanical, thermal and tribological properties. However, their processing is generally challenging, especially for specialty polymers like Polyetheretherketone (PEEK), Polyaryletherketone (PAEK) etc. mainly because of unavailability of a right kind of solvent which restricts exploitation of solution impregnation technique. Having very high melting points along with high melt-viscosity and high oxidation tendency, the possibility of melt-impregnation also gets eliminated. Furthermore, unavailability in fibrous form restricts the processing possibility by commingling technique. The possible options left for developing such composites perhaps are by film-stacking and powder-sprinkling techniques although the major issue of non-wetting at cross-over points remains unaddressed. This paper reports on the maiden effort on developing, characterizing and in depth performance analysis of graphite fabric reinforced PAEK composites. Powder-sprinkling and film-stacking techniques were employed in this work by maintaining identical processing parameters and fabric amount. The comparative performance evaluation led to a conclusion that film-stacking technique excelled in almost all performance properties barring thermal conductivity and thermo-mechanical performance. The performance analysis was based on various techniques such as thermal-conductivity, field emission scanning electron microscopy (FESEM) on polished cross-sections, thermal and thermo-mechanical analysis, mechanical testing, micro-computed tomography, abrasive wear studies etc.

Graphite fabric reinforced PAEK composites by novel impregnation-co-film technique

High performance polymers such as Poly(ether ether ketone) (PEEK), Poly(aryl ether ketone) (PAEK), Poly(ether ketone ketone) (PEKK), etc exhibit high melting points, 343 °C, 373 °C and 338 °C respectively and very high melt viscosity. They do not have appropriate solvents, which could open the ways to process their fabric reinforced composites; by impregnation technique followed by compression molding. Film stacking and powder sprinkling are the only possible techniques, which lead to weak crossover points due to non-wetting by the resin and finally resulting in inferior mechanical and interfacial properties and high amount of voids. In order to solve these problems, a novel technique called impregnation-co-film (ICF) is explored in this work. Polyetherimide (PEI) (10 wt% in dichloromethane solution) pre-impregnated graphite fabric prepregs were used before applying film technique followed by compression molding. The study compares properties such as density, void content, flexural strength, impact strength, Interlaminar shear strength (ILSS), thermal stability (in air) and interface by field emission scanning electron microscopy for the composite prepared with film stacking technique and that by impregnation-co-film stacking technique. It was confirmed that the new ICF technique proved to be significantly promising than the older technique almost in all aspects with 120% improvement in ILSS, 127% in flexural strength and 200% decrease in void content.

A Study of Drilling Behavior of Unidirectional Bamboo Fiber-Reinforced Green Composites

In this study, the biodegradable composite (unidirectional bamboo fiber/polylactic acid) was developed by means of film stacking technique in a hot compression molding setup. The drilling characteristic of the biodegradable composites was experimentally studied by varying different factors. The effect of three different input factors such as feed (8, 16, and 22.4 mm/min), speed (710, 1400, and 2000 rpm), and drill geometry (8-facet, dagger, and slot drill) on the drilling forces (thrust force and torque) was studied. The signals of drilling-induced forces were found to be different for the different drill geometries studied. The slot drill induces minimum forces (thrust force and torque) while making a hole in the composites among all drill geometries. The experimental results reveal that drilling-induced forces reduce at high spindle speed and low feed.

Measurement and analysis of thrust force and delamination in drilling glass fiber reinforced polypropylene composites using different drills

Fiber Reinforced Plastic (FRP) composites are widely used in various engineering fields and applications. FRPs were initially fabricated using thermoset polymers owing to ease of manufacturing. Of late, FRP based thermoplastics is gaining importance due to various factors such as impact resistance, recycling, and an absence of any chemical reaction. In the present investigation, Glass Fiber Reinforced Plastic (GFRP) laminates of woven glass fabric reinforcements with Polypropylene (PP) thermoplastic matrix is manufactured using film stacking technique. To analyze the performance in machining, drilling studies are carried out using a 6 mm diameter twist drill of High Speed Steel (HSS) drill, tipped carbide and solid carbide drill. The drilling experiments are conducted on a CNC Vertical Machining Centre (VMC) to measure and assess the drilling induced thrust force and the respective exit delamination. The drill spindle speed and feed rate are considered as process parameters. To correlate the process parameters with responses, the regression models are developed. The results indicate that the most significant control parameter for process responses and also it shows the developed regression models are highly reliable. The influence of drill materials on the performance of the responses is also discussed in detail.

Hybrid and Nonhybrid Laminate Composites of Sugar Palm and Glass Fibre-Reinforced Polypropylene: Effect of Alkali and Sodium Bicarbonate Treatments

In recent years, the hybrid composites of cellulosic and synthetic fibres are tailored to yield materials with reduced cost and weight. Prior to the fabrication of the hybrid composite, in most case, the cellulosic fibre needs surface modification for proper bonding. Therefore, this study investigates the effect of sodium bicarbonate treatment on the physical and mechanical properties of the hybrid and nonhybrid laminate composites of sugar palm and glass fibre-reinforced polypropylene. The findings will be compared with the conventional alkali treatment. The laminate composites were fabricated using the film stacking technique and hot compression process. Prior to the fabrication process, the sugar palm fibre in it which is naturally woven mat was treated with 4 wt% and 10 wt% alkali and sodium bicarbonate, respectively. All the laminate composites were investigated by tensile, flexural, and impact test, water absorption, and morphological examination. The tensile strength increased with both alkaline and sodium bicarbonate treatments for the hybrid and nonhybrid composites. The increase was more pronounced with the alkaline-treated SPF composite (L03) which displayed the highest value of 61.75 MPa, while that of the sodium bicarbonate-treated SPF composite (L04) recorded 58.76 MPa against 53.01 MPa for the untreated SPF composite (L02). The same trend was observed for the flexural strength. In overall, the alkaline treatment yielded better performance in comparison with sodium bicarbonate treatment.

Delamination Analysis in Drilling of Carbon Fiber Reinforced Polypropylene (CFR-PP) Composite Materials

Abstract Carbon Fiber Reinforced Polymeric (CFRP) composite materials are widely used in the fabrication of major structural parts in aerospace engineering application owing to their specific stiffness and high strength to weight ratio. The drilling process is often used machining operation in order to assemble the parts made by Fiber Reinforced Polymeric (FRP) composite materials. In this work the effect of drilling process variables such as spindle speed and drill feed rate on the drilling induced delamination at exit during drilling of Carbon Fiber Reinforced Polypropylene (CFR-PP) thermoplastic composite is studied in detail. For this study, CFR-PP laminates are fabricated using hot compression molding machine with film stacking technique. The fabricated laminates are tested for physical and various mechanical properties as per the relevant ASTM standards. To analyze the machining performances, the drilling experiments are conducted on a CNC Vertical Machining Center (VMC) using three type of twist drill made with high speed steel (HSS), tipped carbide (TC) and solid carbide (SC) of 6mm diameter. The main objective of this work is to analyze the influence of spindle speed and drill feed rate with respect to drilling induced delamination of drilled hole in CFR-PP composite materials. The empirical relation between machining variables and process responses are developed to predict the process outcome. The observations indicted that the developed regression model is highly suitable to predict the process responses during drilling of CFR-PP composite material. The developed mathematical model may be helpful to reduce the delamination damage which is the most significant undesirable failure during the drilling of CFR-PP material. The influence of machining parameters and their interactions are examined. The significance role of tool materials on the machining characteristic is also discussed in detail.

Comparison of falling dart and Charpy impacts performances of compatibilized and not compatibilized polypropylene/woven glass fibres composites

The effect of the matrix/fibre interface strength on the in-plane and out-of-plane impact performances of glass woven fabric/polypropylene laminates, prepared by means of film stacking technique, was investigated. The interface strength between polymer and fibres was varied by means of a coupling agent added to two different polypropylene grades in order to evaluate its contribution to the impact resistance of the laminates. The static characterization showed that the flexural strength of compatibilized laminates was higher with respect to that of composites based on neat matrices. On the contrary, composites with low interface strength between fibres and polymer showed a strong improvement in impact resistance, in both Charpy and falling dart impact tests. This was related to the possibility of fibres to slip into the matrix and dissipate energy through friction, and to the improved capability to bear load before fibre failure, allowed by the limited propagation of cracks through the laminate. The damage after impact was assessed by means of micro-computed tomography, which elucidated the role of the weak matrix/fibre interface in improving the impact resistance.

Effects of fabric structure on the formability characteristics of thermoplastic composites under various process conditions

Thermoplastic composites are broadly utilized for structural and automotive applications due to their higher specific strength and modulus, higher strain to failure, recyclability, and unlimited shelf life. This study investigates the effects of fabric structure on the forming behaviour of glass fabric reinforced polypropylene composites during the sheet forming of a doubly curved shape. Stamp forming, a novel thermoforming technique, is mostly used for hemispherical forming of thermoplastic composites. The study also investigates the influence of process parameters such as die temperature, blank temperature, and blank holder force on sheet formability. Forming ratio, thickness distribution, material draw-in, and punch force were used for the evaluation of the formability of composites. Conventional and novel plain weave glass fabric reinforced polypropylene composite laminates were fabricated using the film stacking technique. Thermo-stamp forming experiments were conducted on the basis of the Taguchi’s L9 orthogonal array. Experimental results revealed better forming characteristics by the novel glass fabric reinforced composite than for the conventional glass fabric reinforced composite. Production of defect-free components under high die temperature, low blank holder force, and medium blank temperature process condition was observed.

Understanding and predicting the diffusivity of organic compounds in polydimethylsiloxane material for passive sampler applications using a simple quantitative structure-property relationship model.

The diffusivity of 145 compounds in polydimethylsiloxane (PDMS) material was determined in the laboratory using a film stacking technique. The results were pooled with available literature data, providing a final data set of 198 compounds with diffusivity (DPDMS ) spanning over approximately 5 log units. The principal variables controlling the diffusivity of penetrants were investigated by comparing DPDMS within and between different homologous series. The dipole moment, molecular size, and flexibility of penetrants appear to be the most prevalent factors controlling a compound's diffusivity. A nonlinear quantitative structure-property relationship is proposed using as predicting variables the molecular volume, the number of rotatable bonds, the topological polar surface area, and the number of O and N atoms. The final relationship has a correlation coefficient of R2 = 0.81 and a mean absolute error of 0.26 m2 s-1 (log unit), approaching the average error for the experimentally determined values (0.12 m2 s-1 ). The model, based on a heuristic approach, is ready for use by analytical chemists with no specific background in theoretical chemistry (notably for passive sampler development). Environ Toxicol Chem 2018;37:1291-1300. © 2018 SETAC.

Poly(lactic acid)/areca fiber laminate composites processed via film stacking technique

ABSTRACTBio‐based laminate composites, consisting of alternatively stacked poly(lactic acid) (PLA) sheet and randomly oriented areca fiber mat, were processed via film stacking technique (FST). FST was chosen as it is a commercially viable, low energy‐intensive process for fabricating fiber‐reinforced composite, thereby advocating environmental sustainability. Laminate composites exhibited mechanical strength of 6.5 MPa at 16 wt % fiber loading. Crystallinity of as‐received PLA sheets was found to be 26% due to the presence of ∼30 wt % inorganic filler, and showed further enhancement to 50% upon the addition of 22 wt % areca fiber. Dynamic mechanical analysis showed higher glass transition temperature (83 °C) for PLA sheets, mainly due to the presence of higher filler content. This work demonstrates the use of bio‐based laminate composite processed at the lowest possible temperatures as viable alternatives to thermoplastic polyolefins in automobiles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45795.

Flexural and low velocity impact characterization of thermoplastic composites based on PEN and high performance woven fabrics

Poly(Ethylene 2,6‐Naphthalate)—PEN has been used as matrix for laminates with the aim to develop woven fiber reinforced composites with a service temperature as high as 100°C. Three different classes of fibers have been considered as reinforcement in woven fabric form: carbon, polymers (Twaron and Vectran) and mineral (basalt). Composites were manufactured by using the film stacking technique, alternating layers of balanced plain weave fabrics (0/90) and films of amorphous PEN. The manufacturing process was optimized to obtain a good impregnation of fibers and very low void content. Static flexural tests, dynamic mechanical analysis and low velocity impacts were used to characterize the mechanical behavior of the composites. The flexural modulus and strength of laminates resulted to be very high, in particular for the PEN/Carbon and PEN/Basalt systems. The storage modulus from the dynamic mechanical analysis indicated that 100°C is a suitable service temperature for all configurations. The impact resistance of the composites showed a different trend with respect to static tests, since PEN/Basalt and PEN/Aramid exhibited the best performances. These results prove that PEN is a viable option for the production of structural composites as replacement of thermosetting matrices due to its high performance/cost ratio, in particular when combined with basalt fibers. POLYM. COMPOS., 39:2942–2951, 2018. © 2017 Society of Plastics Engineers

Effect of temperature on static and low velocity impact properties of thermoplastic composites

Abstract In this work, thermoplastic composites based on poly(ethylene 2,6-naphthalate) (PEN) have been investigated with the aim to elucidate the effect of temperature on static and impact properties. The matrix was reinforced with four different high performing woven fabrics based on carbon, Twaron, Vectran, basalt fibres. Composites were manufactured by using the film stacking technique, alternating layers of balanced plain weave fabrics (0/90) and films of amorphous PEN, keeping the fibre volume fraction around 40%. The compression moulding process was optimized to obtain optimal fabric impregnation and to keep the void content lower than 1%. The structural response was evaluated at 20 °C, 60 °C and 100 °C by means of static flexural and low velocity impact tests. Dynamic mechanical scans (DMA) were also performed to evaluate the stiffness of the laminates at temperatures ranging from – 80 °C to 230 °C. The flexural modulus and strength of laminates resulted to be very high in proportion with the fibre stiffness. The flexural behaviour was affected by the temperature but a limited reduction of the stiffness (lower than 20%) was exhibited by all but PEN/Vectran up to temperatures of 100 °C. PEN/carbon resulted the best performing system at each testing temperature (flexural modulus equal to 38.8 GPa, flexural strength equal to 714 MPa at 20 °C). Results from DMA tests demonstrated a satisfactory agreement with static tests (differences within ±13%, except that for PEN/Vectran). The impact resistance of the composites was found to depend on the fibre type, temperature and interface strength. PEN/basalt resulted the best performing composite followed by PEN/Twaron (perforation energy at 20 °C: 44.3 J and 38.2 J, respectively). The PEN/carbon laminate exhibited the lowest impact performance but, unlike PEN/basalt and PEN/Vectran, the impact resistance improved with the increasing temperature.

Effects of Surface Modification on the Mechanical Properties of Flax/β-Polypropylene Composites.

The effects of surface treatment of flax fibers featuring vinyltrimethoxy silane (VTMO) and maleic anhydride-polypropylene (MAPP) on the mechanical properties of flax/PP composites were investigated. α-polypropylene (α-PP) and β-polypropylene (β-PP) were used as matrices for measuring the mechanical properties of the flax fiber/polypropylene (flax/PP) composites. Flax/PP composites composed of double-covered uncommingled yarn (DCUY) were prepared using a film-stacking technique. The influence of surface treatment on the tensile, flexural, impact, and water uptake properties of Flax/PP composites were investigated. MAPP treatment was suitable for flax/PP composites in terms of superior tensile and impact properties. VTMO treatment showed superior flexural properties and less influence on the impact properties after moisture absorption.

Fabrication and mechanical properties of self-reinforced polyester composites by double covered uncommingled yarn

Self-reinforced poly(ethylene terephthalate) (srPET) composites composed of double covered uncommingled yarn that was prepared through cowrap spinning were hot pressed using a film stacking technique. The optimal consolidation temperature for manufacturing lamina was determined to be 2408C and resulting in the adequate impregnation and reinforcing structural integrity. The srPET laminates that had a plain structure exhibited the excellent tensile responses, whereas those with a twill weaving structure had the highest impact energy absorption. In the plain fabric, there were more interlace points and a higher crook degree of wrap and weft yarns in the periodic unit cell, resulting in more clamp force on the yarns at the interlace points during stretching and more elongation. The srPET composites prepared using basket-weaving structural fabric broke apart and resulted in the lowest impact energy, which can be attributed to the larger gap between two interweaving points that creates a weak path. A strong influence from the weaving structure was observed for the a relaxation of the composites. Ta shifted to a higher temperature because the reinforcing of the fibers and the structural integrity was more effective. POLYM. COMPOS., 00:000–000, 2015. V C 2015 Society of Plastics Engineers

Thermoplastic composites based on poly(ethylene 2,6-naphthalate) and basalt woven fabrics: Static and dynamic mechanical properties

Composites based on poly(ethylene 2,6-naphthalate) and basalt woven fabrics have been investigated with the aim to develop composites with a minimum service temperature of 100°C. Laminates have been manufactured by using the film-stacking technique. A very low void content and a good fabric impregnation has been obtained as confirmed by the morphological analysis performed with scanning electron microscopy. Static flexural modulus and strength have been measured at 20, 60, and 100°C and compared with the dynamic mechanical behavior, evaluated from −100 to 220°C. A very good agreement has been detected between static and dynamic tests, proving that the dynamic mechanical analysis can be used to estimate the flexural modulus in a wide temperature range. Poly(ethylene 2,6-naphthalate)/basalt composites have exhibited (at 20°C) a flexural modulus and strength as high as 20 GPa and 320 MPa, respectively. The flexural modulus and the flexural strength at 100°C have been found to be equal to 18 GPa and 230 MPa, confirming that this system can retain very good mechanical properties at a service temperature of 100°C. POLYM. COMPOS., 37:2549–2556, 2016. © 2015 Society of Plastics Engineers

Mechanical performance optimization through interface strength gradation in PP/glass fibre reinforced composites

A new design for thermoplastic composites based on the gradation of the interlaminar interface strength (IGIS) has been developed with the aim of coupling high impact resistance with high static properties. IGIS laminates have been prepared by properly alternating layers of woven fabric with layers of compatibilized or not compatibilized polymeric films. To prove the new concept, polypropylene (PP) and glass fibres woven fabrics have been used to prepare composites by using the film stacking technique. Maleated PP, able to compatibilize polypropylene with glass fibres, has been used to manage the interface strength layer by layer.The flexural and low-velocity impact characterizations have shown that the presence of the coupling agent in conventional composite structures (prepared with fully compatibilized polymeric layers) improves the static flexural properties through the strengthening of the matrix/fibre interface but considerably lowers the low velocity impact resistance of the composite, in terms of maximum load before fibre breakage and recovered energy after impact. The use of the IGIS design, that grade the interface strength through the laminate thickness, allows to prepare composites with both high flexural properties and high impact resistance, without affecting the balance and type of the reinforcement configuration.

Synchronicity in composite hydrogels: Belousov-Zhabotinsky (BZ) active nodes in gelatin.

Synchronization of motion, task, or communication is responsible for the successful function of many living systems. Composite Belousov-Zhabotinsky (BZ) self-oscillating hydrogels exhibit a sufficiently complex chemical-mechanical feedback to develop synchrony and other dynamical behaviors. In the context of BZ gels, synchrony is the sustained, oscillating oxidation with constant phase of two or more catalyst-immobilized gel segments. However, design criteria to control chemical-mechanical synchronization through patterning of the reaction catalyst are lacking. To characterize the fundamental units of composite device design, the periodic oxidation behavior of isolated nodes, node pairs, and multinode systems were investigated. Isolated nodes of Ru-immobilized gelatin exhibited three distinct, volume-dependent, regimes of oscillation: (i) long period (10-40 min), (ii) biperiod (mix of long and short), and (iii) short period (2.5 min). Node pairs and multinode grids of Ru gelatin were embedded in plain gelatin through a film stacking or 3D printing technique. The fraction of synchronized node pairs decreased with increasing interspace distance. Embedment increased the probability of synchronization, with 100% synchronization for interspace distances of less than 10 times the characteristic length of the reaction-diffusion process. The phase difference between synchronized node pairs transitioned from in-phase at small interspace distances to antiphase at large distances, providing the first experimental verification of antiphase synchrony in composite BZ gels. From these design criteria and fabrication techniques, the chemical-mechanical feedback of BZ composites can be programmed through strategic patterning of the catalyst to build BZ devices for sensor, trigger, or chemical computing applications.

Experimental Determination of the Mechanical Behavior of Glass Fiber Reinforced Polypropylene Composites

Thermoplastic composites have been widely used in structural and engineering applications, due to their high specific strength and stiffness, high strain to failure, better impact strength, shorter processing cycle time, infinite shelf life, and recyclability. This paper discusses the influence of the forming pressure and coupler concentration on the mechanical behavior of glass fiber reinforced polypropylene composite laminates. The Design of Experiments’ (DOE) full factorial approach was adopted for conducting the composite laminate fabrication experiments. The thermoplastic composite laminates were fabricated in a hot compression molding machine, using the film stacking technique. This is an innovative approach to develop thermoplastic composite laminates, using the available low cost raw materials, instead of high end prepreg materials. As per the ASTM standard, the tensile and flexural tests were carried out, in order to evaluate the influence of the parameters on the mechanical behavior of the composite laminates. The Tensile and flexural strengths of the thermoplastic composite laminates were the responses measured to identify the most influencing parameter. The experimental results show that the increase in forming pressure and coupler concentration initially increases both the mechanical properties, and then decreases the properties of the composite laminates. Compared to the coupler concentration, the forming pressure greatly improves both the tensile and flexural properties. Using the Scanning Electron Microscope (SEM), a morphological analysis was carried out to observe the bonding between the matrix and reinforcement.