Search

Highlights In this paper, we created a new molded‐hole process to manufacture holes instead of drilling in unidirectional (UD) carbon fiber reinforced plastics avoid fiber discontinuity. Several open hole tensile (OHT) tests were carried out on specimens with Cross ply (CP) and Quasi‐isotropic (QI) stacking sequence with drilled holes and molded holes. At the same time, we established finite element analysis (FEA) models of drilled‐hole laminate and molded‐hole laminate to characterize the stress field around the hole. The numerical analysis results reveals that the max principal strain distribution around the molded hole has much higher coincidence with fiber axial direction than that in drilled‐hole laminate. Moreover, the OHT strength results of QI specimens indicate that the plates with molded holes were more 50% higher than those with drilled holes. This process will provide reference for molded UD CFRP structure holes. And the numerical model can help engineering designer make OHT strength prediction. A new molded‐hole process for unidirectional prepreg was created. Molded‐hole specimens have higher open hole tensile strength than drilled‐hole pieces. The simulation results were close to the experimental results. [ABSTRACT FROM AUTHOR]

Heat resistant thermoplastic matrices offer potential advantages over thermoset polymers and represent a promising alternative in advanced composite applications. In the present work, the properties of carbon fiber reinforced plastics (CFRPs) based on the developed semicrystalline polyimide R‐BAPB were studied and compared with those of highly heat‐resistant thermoplastic polymers such as amorphous polyetherimide Ultem‐1000 and semicrystalline polyetherketone PEEK. To obtain CFRP, an approach was used basing on the uniform distribution of polymer powders on continuous carbon fibers by electrostatic spraying followed by their impregnation in heated calenders and hot pressing. The thermal and thermomechanical properties of CFRPs based on mentioned above polymers were studied. The effect of temperature on the mechanical behavior of CFRPs, including flexural properties and interlaminar fracture toughness G1C, was investigated as well. CFRPs based on PEEK and R‐BAPB are found to have the highest thermal stability and heat resistance. The maximum flexural strength, which practically does not change in a wide temperature range from −50 to 180°C, is observed for CFRP based on R‐BAPB polyimide. Among the investigated CFRPs, the highest value of interlaminar fracture toughness is shown by CFRPs based on semicrystalline R‐BAPB. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastics (CFRPs) are widely used in the aerospace, automotive, and construction industries. CFRP prepregs (intermediate products) are generally used in CFRP production, with a large number of prepreg cut‐offs being discarded during cutting processes. There is strong demand for a method for recycling carbon fiber prepreg cut‐offs. This paper proposes a method for recycling such material, which is characterized by low cost and high added value, in order to foster the development of a recycling‐oriented society. We prepare carbon tapes (CTs) by cutting discarded cut‐offs according to their size so as to maximize fiber length. Using a simple water CT dispersion method, we fabricate uniform CT sheets and mold a recycled CT‐reinforced composite (R‐CT‐RC). Sample prototyping and mechanical characteristic testing indicate that this R‐CT‐RC is characterized by low recycling cost and desirable mechanical properties. Recycled CT‐reinforced composite with thermoplastic (R‐CT‐RC/TP), which is prepared by adding thermoplastic resin between CTs, can be re‐molded and therefore readily re‐recycled. [ABSTRACT FROM AUTHOR]

Developing high‐performance polymer (HPP) with improved properties by green processing method is one of the core parts of HPP research. In this paper, a new monomer (4,4′‐((propane‐2,2‐diylbis(4,1‐phenylene))bis(oxy))dibenzaldehyde (PBhDCI)) of high‐performance aromatic nitrile‐based (AN) resins with good solubility in ethanol was designed. The rheological analysis showed that PBhDCI is suitable for the processing by laminating process. The cured resins and the corresponding carbon fiber reinforced plastics (CFRP) showed outstanding thermal and mechanical properties. The thermal decomposition temperature (T5%) of the cured PBhDCI under nitrogen up to 510°C, the glass transition temperature (Tg) of both resin matrix and CFRP exceeds 500°C, and the flexural strength and modulus of CFRP were 507 ± 5 MPa and 59 ± 2 GPa. This work will offer some guidance for the preparation of high‐performance resins and corresponding CFRP with a green processing and high thermal and mechanical properties. [ABSTRACT FROM AUTHOR]

In this work, a numerical simulation was carried out to analyze the influence of contact points as well as fibers breakage on the transverse conductivity of unidirectional (UD) carbon fiber reinforced plastics (CFRP). The analysis is based on the calculation of the distribution of the electric scalar potential on a geometry inspired by a cross‐section along the axis of the fibers taken by scanning electron microscopy (SEM) on a CFRP. The observation of the cross‐section allows us to capture the microstructure of the material which served as a basis for our model, in which numerical analysis using the finite element method (FEM) was performed. This simulation allows us to highlight the electric current pathways and evaluate their influence on both longitudinal and transversal electric conductivity. The obtained results give a good agreement with those found in the literature. [ABSTRACT FROM AUTHOR]

Carbon fiber‐reinforced polymers are one of the lightweight materials used in structural design due to their exceptional mechanical performances. The drilling operation is indispensable as it facilitates the assembling of various manufactured components. However, drilling of fibrous laminates is deemed difficult in comparison to the traditional metals because of the anisotropic and non‐homogeneous nature. The present work addresses the parametric effect on the drilled hole delamination and further reduces it with an optimal combination of parameters for multi‐objectives using different multi‐criterion decision‐making techniques. Initially, the response surface‐based regression model of delamination as a function of three static inputs has been developed, further revised with induced thrust as well as mean torque for the improvisation of the prediction capability. Finally, for the overall improvement, a decision‐making model has been used that includes grey relation analysis, technique for order performance by similarity to ideal solution, and VIšekriterijumsko Kompromisno Rangiranje method. The delamination was found to be minimum at a low drill point angle (100°), high spindle rotation (2150 min−1), and low feed rate (0.025 mm/rev) due to reduced thrust force. The mean absolute prediction error was significantly improved considering root mean square torque rather than axial thrust with process variables. [ABSTRACT FROM AUTHOR]

Carbon fiber is an ideal candidate for preparing electrode of structural supercapacitors, while its low specific surface area is a vital factor which restricts energy storage performance. In this study, MnOOH nanowires (MnOOH‐NWs) are in‐situ deposited onto the woven carbon fiber fabric (WCF) surface through an effective one‐step hydrothermal treatment to prepare MnOOH‐NWs modified WCF (MnOOH‐NWs@WCF) structural supercapacitor with appreciable electrochemical performance. The areal capacitance of MnOOH‐NWs@WCF structural supercapacitor reaches 77.1 mF/cm2, which is two orders of magnitude higher than that made from neat WCF electrode. The increase in areal capacitance is primarily due to the presence of conductive networks and abundant ion storage sites constructed by the MnOOH‐NWs. Meanwhile, flexural strength and modulus of the MnOOH‐NWs@WCF structural supercapacitor are 30.3 MPa and 1.8 GPa, respectively. Interestingly, the resultant structural supercapacitor also enables electromagnetic interference (EMI) shielding based on the conductive networks constructed by the WCF and MnOOH‐NWs, and the maximum EMI‐shielding effectiveness (EMI‐SE) is 59.1 dB. Consequently, a highly integrated multi‐functional structural supercapacitor is developed, which cannot only be applied as energy storage module and load bearing component but can also be adopted to protect electronic devices from the electromagnetic pollution. [ABSTRACT FROM AUTHOR]

The comminution of carbon fiber reinforced plastics (CFRP) is a central process step for almost all recycling processes. Size reduction creates a specific surface that serves as a measure in particular of the size reduction success of fines. The article shows the comminution from 1 m edge length in the feed material down to a target product size of less than 100 µm by means of three‐stage comminution. The challenges of granulometric characterization of the comminution products and the associated evaluation of the comminution success are specifically addressed. [ABSTRACT FROM AUTHOR]

Due to the continuing trend towards lightweight construction, more and more carbon fiber reinforced plastics (CFRP)‐containing waste is generated, particularly in the areas of transportation, energy technology as well as in the mechanical engineering or leisure sector. For CFRP‐containing waste with thermoplastic matrix, a closed‐loop recycling by regranulation could be demonstrated. Under multi‐stage mechanical stress, the CFRP material was comminuted to a defined granule size. This granulate from secondary material was converted by means of a special process in an injection molding complex into new components. [ABSTRACT FROM AUTHOR]

The production of carbon fiber reinforced (CFR) anionic polyamide 6 (APA6) plates by thermoplastic resin transfer molding (T-RTM) processing is highly sensitive to the presence of polymer additives such as flame retardants (FRs). However, APA6 is flammable, and therefore, it is mandatory to protect the polymer matrix, especially if the produced materials are intended for aerospace applications. Typically used FR for PA6 cannot be incorporated in the T-RTM processes. With hexaphenoxycyclotriphosphazene, an incorporable and effective FR additive for CFR APA6 was discovered. Cone calorimetry measurements indicate a char formation-based mechanism, and the flame retardancy was further confirmed with limiting oxygen index tests, classification by UL94 (V-0), and FAR25 tests. The influence of this FR on the thermal (thermogravimetric analysis and differential scanning calorimetry) and mechanical behavior (flexural, compressive and ultimate tensile strength, and Charpy impact tests) on CFR APA6 produced via T-RTM processing is evaluated and indicates no interaction with the APA6; it works as a passive filler. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]