Carbon Fiber Composite Samples Research Articles

Hierarchical aerospace epoxy composites of carbon fiber and hyperbranched filler: toughening behavior from nanocomposites to composites

In this work the effect of a glassy hyperbranched polymer (G_HBP), characterized by a Tg higher than room temperature (∼77 °C), on the mechanical properties of a patented epoxy resin was investigated. To define an optimized filler concentration, three different G_HBP contents were prepared by a solvent-free technique and improvements of fracture toughness compared to the neat matrix (ΔKC ∼ 16 % and ΔGC ∼ 39 %) and to the corresponding laboratory solvent-based procedure. The solvent-free procedure and the found optimal filler content were considered to manufactured long carbon fiber composite samples of both neat and G_HBP loaded matrix later tested and compared in terms of tensile and flexural properties, as well as fracture toughness performance. Mode I and II interlaminar fracture toughness tests were carried out, revealing remarkable increase of both onset and propagation (ΔGIConset ∼ 29 % and ΔGICprop ∼ 53 %) and preserving the GIIC value (ΔGIIC∼+ 6 %). Validation tests in compression after impact were also performed and analyzed.

Analysis of cross-sections of PCM samples with embedded FOSS

In this work, experimental studies of the internal structure of woven fabric reinforced fiberglass and carbon fiber composite samples with embedded optical fiber were carried out. It is known that for the unidirectional composites the most significant distortion of the structure of the host material takes place when the optical fiber is embedded perpendicular to the direction of the reinforcement of the composite material layers. However, the internal structure of the composites with woven layer reinforcement scheme is significantly different. And the embedding of such a foreign object as an optical fiber can cause a basically other, as compared to unidirectional composites, change in the internal structure. Cross-sectional studies were performed using an optical microscope. The analysis of cross-sections of PCM samples was carried out with the aim of studying the changes in the structure of the layered composite with woven fabric reinforcement due to the embedding of the fiber-optic sensors. A comparison of the obtained images showed that the microstructure of the studied samples is better seen on polished surfaces. In the absence of polishing on a number of samples, the optical fiber is not visually noticeable or poorly distinguishable. Analysis of the obtained images showed that there is an insignificant distortion of the internal structure of the material in the area with embedded optical fiber without the formation of a resin pocket for all studied GFRP samples. At the same time, when analyzing CFRP samples, the effect of embedding of the optical fiber on the microstructure of the composite was not observed.

Synthesis and Characterization of Hybrid CF/MWCNTS/Epoxy Resin Composite System

In the present investigation, two methods were used for addition multiwall carbon nanotubes (MWCNTS) into carbon fiber (CF)/epoxy resin composite system. The mechanical properties of the prepared samples were compared to show the best method for addition of MWCNTS from point of view of mechanical properties. The introduction of carbon nanotubes (CNTs) into fiber reinforced polymer composites has been achieved mainly via two routes: mixing CNTs entirely throughout the matrix (matrix modification) or attaching CNTs onto reinforcing fibers (interface modification). In all previous references the addition of CNTs occur through one route from the two routes but in this research, we introduced MWCNTS into CF/epoxy resin composite through the two routes at the same time. Three CF composite samples were prepared CF/epoxy resin composite (C1), CF/1wt% MWCNTS /epoxy resin composite (C2) in which MWCNTS added via one route (epoxy resin system) and the third sample was CF/1wt% MWCNTS / epoxy resin composite (C3) in which MWCNTS added via two routes (epoxy resin and CF fabric). The result shows that the mechanical properties of C3>C2>C1, for example, the flexural strength of C3 higher than C2 by 19% and C2 higher than C1 by 51% respectively. This is because addition MWCNTS via two routes increase the ability of good mixing of CNTS with epoxy resin and good dispersion of CNTs into the CF fabric surface and this leads to improve the interface bonding between the CF and epoxy so improve the mechanical properties.

Gasification and removal of carbon materials and redeposited boron–carbon layers exposed in an oxygen–ozone mixture

The results from experiments on measuring the rate of gasification for carbon and boron–carbon films and carbon fiber composite (CFC) exposed in oxygen–ozone mixtures are presented. The rate of gasification is 0.4–0.6 μm h–1 (at temperatures of 220–250°C, a pressure of 0.3 atm, and an ozone concentration of 0.6 at %) for carbon films; plane CFC samples; gaps 1 and 2 mm wide with walls of stainless steel; and gaps 1 mm wide with walls of CFC. It is 15 μm h–1 for plane CFC at a temperature of 250°C, a pressure of 1 atm, and an ozone concentration of 10 at %. The rate of gasification for boron–carbon films is from 3 to 30 nm h–1 for B/C ratios of 2.1 to 0.8 (at 250°C, 1 atm, and ozone concentration of 10 at %).

Unsupervised learning for classification of acoustic emission events from tensile and bending experiments with open-hole carbon fiber composite samples

Abstract Widespread use of composites for structural applications is hindered by the inability to fully understand and predict the materials response. The uncertainty in composite materials response is largely due to variability in the initiation and propagation of damage. To develop new tools for design with composite materials, techniques for identifying damage modes during operation are needed. While there is a large body of work on analysis of acoustic emission (AE) from different materials and different loading cases, the current research is focused on applying unsupervised learning for separating AE into a maximum number of groups with distinct evolution. AE data was collected during tensile and bending experiments on carbon fiber reinforced epoxy specimens with different material configurations. The unsupervised learning algorithms successfully identified AE groups with distinct initiation and evolution. With damage mechanisms inferred from load response and from deformation fields obtained with digital image correlation (DIC), strong correlations between the behaviors of the groups and the damage mechanisms were observed and are discussed.

Research on EIS-Based Anomaly Detection Technique for Composite Materials

The application of advanced composite materials in airplane is becoming more and more. Along with the increase of its service time, it may be abnormal. It needs to take an anomaly detection. The electrical impedance spectroscopy (EIS) is applied to the anomaly detection of composite material components in airplane. A uniplanar sensor with double-electrode and two carbon fiber composite samples are made, an experiment circuit is designed. In order to verify the effectiveness of the experimental circuit, the EIS of the Randles unit model circuit is measured, as well as the two composite material samples using the dual-electrode measurement method. The picture of EIS is drawn in Matlab and comparison and analysis are carried out. The preliminary experimental results indicate that the anomalies can be seen by measuring the EIS of the composite materials. It is feasible for the EIS to be applied in the anomaly detection of the composite materials in airplane.

Tungsten coatings under high thermal loads in JET and Magnum-PSI

During the C28–C30 campaigns the ITER-like wall (ILW) was periodically inspected by an in vessel inspection system without breaking the vacuum. After these campaigns the JET chamber was opened and the wall was inspected with a high resolution camera. The marker tiles were removed from the chamber and were inspected in the beryllium handling facility. The overall picture of the ILW after more than 3000 pulses looks good. However there are a few modifications such as the deposition of Be on some W coated tiles, local destruction of the W coating by runaway electrons in an emergency shutdown, arcing on particular W coated tiles, and small delaminations on G6 and G8 divertor tiles. These aspects, together with the results of high heat flux tests carried out with W coated carbon fiber composite samples in Magnum-PSI, are discussed in the paper.

탄소나노튜브로 보강된 탄소섬유복합재의 제조 공정과 모드 1 파괴인성

탄소나노튜브로 보강된 고분자 수지에 대한 연구는 지난 20년간 활발히 수행되어 왔다. 또한 이를 이용하여 탄소섬유복합재의 물성을 증대시키기 위한 연구도 최근 그 영역을 넓혀가고 있다. 탄소섬유복합재는 탄소섬유의 비약적인 발전으로 섬유 방향의 기계적 물성은 상당히 만족할 만한 수준에 도달했으나, 수지에 의해 좌우되는 기계적 물성은 아직 기대에 못미치고 있다. 특히, 층간의 분리 (delamination)는 탄소섬유복합재의 가장 전형적이며 치명적인 파손의 원인중 하나이다. 이 층간분리에 대한 저항성을 알아보는 모드 1 파괴인성 실험 (혹은 double cantilever beam, DCB test)을 다양한 작용기로 기능화된 SWNT가 첨가된 탄소섬유복합재 시편에 대하여 수행하였다. 부직포 형태의 탄소나노튜브층을 이용한 시편의 경우 10.6%의 파괴인성 증대를 보였다. For the last twenty years, nanocomposites composed of polymer matrices reinforced with carbon nanotubes (CNTs) have been an active research area. Also, the polymeric nanocomposites reinforced with CNTs are being investigated to be used matrices of carbon fiber composites. Carbon tiber composites have achieved advanced properties in the direction of carbon fibers due to enhanced carbon fiber properties. However, the matrix dominated properties need to be improved further to fully utilize the advanced carbon fiber properties. In particular, delamination is a typical and critical reason for fracture of carbon fiber composites. Mode I fracture toughness test which is also often called double cantilever beam (DCB) test shows the resistance to delamination of carbon fiber composites and this test is performed on carbon fiber composite samples incorporated with carbon nanotubes functionalized with various functional groups. The specimens with mat-like CNT layers showed the increased fracture toughness by 10.6%.

Fiber erosion of carbon fiber composite exposed to simulated ITER-relevant thermal impact by high-intensity pulsed ion beam

A carbon fiber composite (CFC) was thermally tested with high heat flux on a high-intensity pulsed ion beam (HIPIB) apparatus, simulating the ITER specific thermal impacts in divertor region during normal operation or on first wall during off-normal events. The HIPIB shot is capable of delivering an extremely high heat flux onto the target materials at a heat flux parameter of up to 300 MW/m 2 s 1/2 covering most of the ITER heat loads. The surface morphology of CFC samples after the HIPIB exposure and the resultant weight losses were investigated using scanning electron microscope (SEM) and microelectronic balance, respectively. Moreover, Raman spectroscopy was used to study the microstructural changes of the exposed samples. Comparative tests were also carried out on pure graphite samples. It is found that the CFC samples underwent a severer net weight loss in comparison with the graphite under multi-shot exposure, where the material removal from the CFC proceeded in the form of carbon fibre exfoliation and/or fracture along with matrix spallation as the high heat flux exposure prolonged up to 10 shots. The fibre erosion process is attributable to the anisotropic thermophysical properties of carbon fibre and its interface bonding strength with graphite matrix though the reinforcing carbon fibre ensures excellent high-temperature strength of the CFC over the graphite.

FIRE DAMAGE ON CARBON FIBER MATERIALS CHARACTERIZED BY THZ WAVES

We apply THz imaging technology to evaluate fire damage to a variety of carbon fiber composite samples. The majority of carbon fiber materials have polarization-dependent reflectivities in the THz frequency range, and we show how the polarization dependence changes versus the burn damage level. Additionally, time domain information acquired through a THz time-domain spectroscopy (TDS) system provides further information with which to characterize the damage. The technology is discussed in terms of non-destructive testing applications to the defense and aerospace industries.

Wide‐angle x‐ray scattering study of heat‐treated peek and peek composite

AbstractWe report the results of a study of poly(etheretherketone) (PEEK) neat resin and APC‐2 carbon fiber composite samples which were processed from the melt and then subjected to a variety of thermal treatments. Wide‐angle x‐ray scattering was used to study the effects of quenching and annealing treatments. For both neat resin and composite, annealing resulted in perfection of the crystalline microstructure. In addition to the crystalline and amorphous scattering usually observed, disorder is frozen‐in by fast cooling after heat treatment. The disordered component is detected as an additional low‐angle scattering peak at 14 degrees, well separated from the crystalline reflections, and is observed in low molecular weight material synthesized in our laboratory, and in commercially available neat resin PEEK and APC‐2 carbon fiber composite samples. When disordered material was subsequently heated above the glass transition, and then cooled very slowly, only the crystalline and amorphous scattering remained. Application of stress also resulted in formation of the disorder in the necked down regions of samples drawn in tension, suggesting that residual stresses may occur as a result of rapid cooling after heat treatment.