Carbon Fiber Tube Research Articles

Additive Manufacturing Offers New Opportunities in UAV Research

Multi-rotors vehicles have become a consolidated reality in modern aeronautical field. These small helicopters consist in a fuselage “hanged” under a set of fixed pitch propellers each powered by an electric motor. These vehicles have great potentials and research in this topic is increasing aimed to reduce the structure weight to maximize flight time, range and payload.Multi rotor components represent a key challenge for 3D modeling, optimization and additive manufacturing: they mainly consist in complex shapes where the most important feature are robustness and lightweight. Usually produced in small series, for example, eight parts for a single prototype, they almost need to be able to interface different materials.The work here presented shows the advanced research conducted in cooperation between Altair Engineering and Politecnico di Torino to develop vital components for the structure of a multi-rotor: they represent a challenge because the main need is to interface arms, consisting in carbon fiber tubes, with motor or frame, both made in 7075 Alloy.The use of topology optimization techniques plays a key role to minimize the weight of the components and to improve the productivity of the machines. Moreover, Additive manufacturing (FDM with Sharebot NG) allows producing more parts in less time improving the cost effectiveness of the project. The process will be described from a simple characterization of the anisotropic properties of 3-D printed specimens to FEM analysis of the preliminary design of the component and to the optimization phase performed with Altair Optistruct code.An important role is played from the Altair tool used for the preliminary design: Inspire. This tool is conceived to generate structural efficient concepts quickly and easily to obtain lighter designs and eliminate structural design problems and finally provide input files for 3-D printers.

Design and Experimental Study of a Composite Materials Micro-Deformation Measurement Device

In the space environments, the size and weight of composite materials will produce small changes. In order to measure the small changes accurately, a micro-deformation measurement device has been designed. The carbon fiber tube was made from cyanate ester resin or epoxy resin was tested in vacuum and hygrothermal environments. The deformation in the vacuum test is -1.7 to 3.8 microns, in the hygrothermal test, the deformation is -1.3 to -6.4 microns. The same as theoretical analysis, the environmental stability of cyanate ester resin better than epoxy resin.

New shielding configurations for a simultaneous PET/MRI scanner at 7T

Understanding sources of electromagnetic interference are important in designing any electronic system. This is especially true when combining positron emission tomography (PET) and magnetic resonance imaging (MRI) in a multimodality system as coupling between the subsystems can degrade the performance of either modality. For this reason, eliminating radio frequency (RF) interference and gradient-induced eddy currents have been major challenges in building simultaneous hybrid PET/MRI systems. MRI requires negligible RF interference at the Larmor resonance frequency, while RF interference at almost any frequency may corrupt PET data. Moreover, any scheme that minimizes these interactions would, ideally, not compromise the performance of either subsystem. This paper lays out a plan to resolve these problems.A carbon fiber composite material is found to be a good RF shield at the Larmor frequency (300MHz in this work) while introducing negligible gradient eddy currents. This carbon fiber composite also provides excellent structural support for the PET detector components. Low frequency electromagnetic radiation (81kHz here) from the switching power supplies of the gradient amplifiers was also found to interfere with the PET detector. Placing the PET detector module between two carbon fiber tubes and grounding the inner carbon fiber tube to the PET detector module ground reduced this interference. Further reductions were achieved by adding thin copper (Cu) foil on the outer carbon fiber case and electrically grounding the PET detector module so that all 3 components had a common ground, i.e. with the PET detector in an electrostatic cage. Finally, gradient switching typical in MRI sequences can result in count losses in the particular PET detector design studied. Moreover, the magnitude of this effect depends on the location of the detector within the magnet bore and which MRI gradient is being switched. These findings have a bearing on future designs of PET/MRI systems.

Three-Degree-of-Freedom MR-Compatible Multisegment Cardiac Catheter Steering Mechanism

This paper presents a novel MR-compatible 3-DOF cardiac catheter steering mechanism. The catheter's steerable structure is tendon driven and consists of miniature deflectable, helical segments created by a precise rapid prototyping technique. The created catheter prototype has an outer diameter of 9 Fr (3mm) and a steerable distal end that can be deflected in a 3-D space via four braided high-tensile Spectra fiber tendons. Any longitudinal twist commonly observed in helical structures is compensated for by employing clockwise (CW) and counter clockwise (CCW) helical segments in an alternating fashion. A 280μm flexible carbon fiber rod is used as a backbone in a central channel to improve the structure's steering and positioning repeatability. In addition to the backbone, a carbon fiber tube can be inserted into the structure to a varying amount capable of changing the structure's forcibility and, thus, providing a means to change the curvature and to modify the deflectable length of the catheter leading to an extension of reachable points in the catheter-tip workspace. A unique feature of this helical segment structure is that the stiffness can be further adjusted by appropriately tensioning tendons simultaneously. An experimental study has been conducted examining the catheter-tip trajectory in a 3-D space and its positioning repeatability using a 5-DOF magnetic coil tracking system. Furthermore, MRI experiments in a 1.5-T scanner confirmed the MR-compatibility of the catheter prototype. The study shows that the proposed concept for catheter steering has great potential to be employed for robotically steered and MR-guided cardiac catheterization.

Effect of callus development on the deformation of external fixation frames

We designed a sensor that measures the bending moments at the articulations and the torque of the rod of a Hoffmann II® external fixation. We considered the effect of the callus formation in the stabilisation of a "fracture-fixation system." Four Hoffmann II® frame configurations were mechanically tested. Two carbon fibre tubes represent the bone fragments (length 180mm, outer diameter 25mm, inner diameter 19mm). The callus is represented by the interposition of springs of different rigidity (10-405N/mm) in the fracture gap between the tubes. The deformation of the frame is in inverse proportion to the stiffness of the callus; the slope of the curve drops rapidly during early development of the callus, to reach a plateau after some 50% of recovery of the normal mechanical characteristics of the bone. This simulation supports the theoretical approach, i.e. the external frame resists larger stresses at the start of the fracture healing. Over a callus stiffness of some 200N/mm the pattern of the curves remains similar, regardless of the frame configuration. An optimisation of the frame is possible, adapted to the actual mechanical situation of the callus. A monitoring system is deemed reliable after making sure that the elementary components behave the same way in the clinical condition as in the laboratory. In an experimental set up we confirmed its reliability in a clinical-like situation.

CFRP strengthening of a railway concrete trough bridge – a case study

This paper presents an upgrading and monitoring of a Swedish concrete railway bridge. The methods used for the upgrading as well as for the monitoring are innovative and new. Carbon fibre tubes are inserted in holes in the bridge deck, drilled in the transverse direction of the slab at a location ca. 40 mm from the top. Carbon fibre NSMR bars are bonded in transverse grooves in the soffit of the slab. Both methods are intended to increase the transverse bending moment capacity of the troughs' bottom slab in the ultimate limit state. Monitoring is performed to verify the effectiveness of the strengthening and to understand the behaviour of the bridge. However, for obvious reasons, monitoring is only carried out in the SLS (service limit state). Even though only marginal effects of strengthening could be recorded in the SLS, both the strengthening and monitoring were considered successful at a cost of approximately 8% of the total cost of a new bridge replacement.

Finite Element Analysis and Experimental Investigation of Carbon Fiber Composite Circular Tube

In this paper, A 3-D numerical model of a circular tube is established, which is made of carbon fiber composite materials whose inner diameter is 43mm and outer diameter is 45mm. The behaviour of axial compression and bending load cases are analyzed under the theory of mechanics of materials and theory of classical laminate plate. Results of axial compressive stiffness and bending stiffness agree well with the experimental data,showing that the FEM simulation used in this paper is an efficient and reliable tool to calculate and predict the behaviour of carbon fiber tube.

Modelling the side impact of carbon fibre tubes

Metallic tubes have been extensively studied for their crashworthiness as they closely resemble automotive crash rails. Recently, the demand to improve fuel economy and reduce vehicle emissions has led automobile manufacturers to explore the crash properties of light weight materials such as fibre reinforced polymer composites, metallic foams and sandwich structures in order to use them as crash barriers. This paper discusses the response of carbon fibre reinforced polymer (CFRP) tubes and their failure mechanisms during side impact. The energy absorption of CFRP tubes is compared to similar Aluminium tubes. The response of the CFRP tubes during impact was modelled using Abaqus finite element software with a composite fabric material model. The material inputs were given based on standard tension and compression test results and the in-plane damage was defined based on cyclic shear tests. The failure modes and energy absorption observed during the tests were well represented by the finite element model.

Experimental Investigation of a Large-Scale Composite Riser Tube Under External Pressure

A collapse pressure test was conducted on a full-scale diameter prototype composite offshore drilling riser. The test specimen was a carbon fiber-epoxy filament-wound tube, approximately 56.4 cm outside diameter and 3.05 cm wall thickness. The tube was subjected to external water pressure up to collapse. The purpose of the test was to confirm the external pressure capacity of the specimen and to provide a basis for verification and calibration of analytical estimates of the collapse pressure of large scale carbon fiber tubes. The specimen was instrumented with strain gauges on both the outside and inside walls of the tube. This paper describes the test specimen and presents key results of the test.

탄소섬유관으로 구속된 무근 원형 보의 휨성능에 관한 실험적 연구

탄소섬유관으로 구속된 원형 무근콘크리트 부재는 콘크리트에 효과적인 횡구속을 제공하며, 섬유의 우수한 역학적 성질로 인하여 기존의 철근을 대체할 수 있는 우수한 합성부재이다. 본 논문에서는 탄소섬유관으로 구속된 원형 무근콘크리트 보에 관한 실험 및 해석연구를 실시하였다. 실험연구에서 시험체는 두께 1.5mm(3장), 2.0mm(4장), 2.5mm(5장) 및 3.0mm(6장)를 변수로 하여 실험을 실시하였다. 구속된 콘크리트의 압축강도를 예측하는 식을 이용하여 본 연구에서는 탄소섬유 관으로 구속된 원형 무근 콘크리트 보의 휨성능을 예측하는 실험식을 제안하였다. Experiments for circular unreinforced concrete beams confined by carbon fiber tubes (CFT) made of carbon fiber sheets were performed. Selected test parameter was thickness of carbon fiber tube: 1.5mm (3 layers), 2.0mm (4 layers), 2.5mm (5 layers), and 3.0mm (6 layers). Based on the test results, an equation for estimating moment capacity of the circular beams confined by carbon fiber tubes was proposed. Comparison results showed good agreement up to 2.5mm (5 sheets) of the CFT thickness.

탄소 섬유관으로 구속된 콘크리트 부재의 신뢰성 해석

본 논문에서는 탄소섬유관으로 구속된 무근 콘크리트 원형 및 각형 기둥에 대한 축하중 및 횡하중 재하 실험을 수행하고, 실험결과를 바탕으로 하여 몬테카를로 해석을 이용한 신뢰성 해석을 수행함으로써 탄소섬유관으로 구속된 무근 콘크리트 원형 및 각형 기둥과 탄소섬유관으로 구속된 철근 콘크리트 원형 및 각형 기둥의 두 가지 경우에 대한 강도저감계수를 예측하였다. 해석 결과, 무근의 경우에는 강도저감계수가 0.7로 예측되었고, 철근이 삽입된 경우에는 강도저감계수가 0.85로 예측 되었다. 이러한 계수값은 원형과 각형인 경우 모두 같은 계수값을 보여주었다. In this study, axial and lateral loading experiments for both circular and square plain concrete columns confined with carbon fiber tube manufactured by carbon filament winding technique were performed. Based on the test results, reliability analyses to estimate strength reduction factors were carried out by utilizing Monte Carlo technique. CASE I was for plain concrete columns confined with the carbon tubes, CASE II was for reinforced concrete columns confined with the carbon tubes. As results, the strength reduction factors, <TEX>${\phi}$</TEX>, were estimated as 0.7 for CASE I and 0.85 for CASE II respectively.

Rf enhancement and shielding in MRI caused by conductive implants: Dependence on electrical parameters for a tube model

Radio frequency (rf) eddy-currents induced in implants made of conductive material might cause significant image artifacts in magnetic resonance imaging (MRI) such as shielding of the lumen of vascular stents. rf alteration near metal parts was assessed theoretically in the approximation of alternating current electrodynamics: The implant was modeled as tube with diameter d(o), resistance R, and reactance Y, constituting the secondary winding of a transformer. The transmitter coil of the scanner acted as primary winding and generated the linearly polarized rf field B1,app. Tube axis was assumed parallel to B1,app. The results of the calculations were as follows: Ninety percent of the applied rf-field amplitude is reached in the lumen at a ratio chi=R/Y approximately 2. A rapid drop occurs with the reduction of chi, whereas a further increase of chi causes only a small effect. With chi approximately 1/d(o)(Y approximately d2o,R approximately d(o)), conditions for rf alteration clearly depend on the diameter of the tube. Inside tubes with smaller diameter, rf shielding is less pronounced. rf alteration increases in good approximation with the square root of the strength of the static field B0. The following experiments were carried out: Tubes of similar diameter (d(o) approximately 8 mm) made of material of different conductivity (Cu, Nitinol, carbon fiber reinforced plastic with three different fiber structures) were examined at B0=0.2 and 1.5 T in water phantoms. Tube axis was aligned perpendicular to B0 and spin-echo technique was applied. Local rf enhancement near the outer surface of the metal tubes was detected applying manual reduction of the transmitter amplitude. Shielding inside a carbon fiber tube with d(o) approximately 8 mm and inside a smaller tube with d(o)=3.3 mm was compared. Both tubes showed the same wall structure and thickness (d(w)=0.4 mm). All measurements confirmed the theoretical results. Consequences for the construction of vascular stents are discussed, as well as problems with image artifacts due to rf enhancement near solid conductive implants.

An infrared line scanning technique for detecting delaminations in carbon fibre tubes

A thermal nondestructive testing method based on an infrared line scanner for cylindrical specimens is presented. A seven-layered carbon-glass fibre tube with an artificial delamination was used as a test sample. A finite difference computational model of the heating of the tube was constructed in order to simulate the measurement and evaluate the capability of detecting delaminations. The numerical results show the temperature difference caused by the delamination to be well above the practical detection limit, which was verified by the actual measurements.

Impact-fatigue behavior of composite tube/metal end fitting bonded joints

The relatively high specific strengths and moduli of advanced composite materials make them an attractive option for use in high speed industrial equipment. Hence, a potential market exists for integrating composites into existing machinery to replace critical metallic components. An application of such is the replacement of a high speed reciprocating steel bodymaker ram with one fabricated from a filament wound carbon fiber tube with bonded steel end fittings. Due to the dynamic forces which are inherent in the operation of high speed machinery, components are often subjected to impact, fatigue, and combined high cycle impact-fatigue. The behavior of composites as well as adhesives subjected to either impact or fatigue is well established. However, the combined impact-fatigue behavior of adhesive joints between filament wound carbon-fiber reinforced epoxy tubes and steel end fittings has not been investigated and is the focus of this study. An impact-fatigue testing machine was designed and fabricated specifically for these tests. The impact pulses generated by the machine closely resemble those of a conventional drop weight impact test machine. In addition, the impact-fatigue machine is capable of completing high cycle impact-fatigue tests (10 6 impacts) within a relatively short period of time by operating in excess of 10 impacts per second. Tests were performed at several impact load levels ranging from 15% to as much as 40% of the joint U ltimate S tatic C ompressive F ailure - L oad. These impact load levels were monitored throughout the specimen lifetime. Furthermore, three bondline thicknesses were investigated to attain an initial indication of the sensitivity to bondline thickness variation. Results indicate that the specimens exhibit an initial plateau region for a number of cycles during which time no decrease in load carrying capacity is measured. After a critical number of impacts, damage becomes apparent as the sample is no longer capable of maintaining the initial load. At this point, these constant-displacement tests show a load drop and a corresponding compliance change is noted as the sample begins to show less resistance to impact. Post-impact compression test results also show this drop in strength and modulus. Further, the percentage of the U ltimate S tatic - C ompressive - F ailure Load being applied dynamically determines the length of the plateau as well as the rate of degradation. Thus, the determination of the performance of composite tube/metal end fitting bonded joints using this impact-fatigue test approach gives information critical for lifetime design of dynamically loaded composite components.

A New Improved Biodegradable Tracheal Prosthesis Using Hydroxy Apatite and Carbon Fiber

A new biodegradable tracheal prosthesis was developed using hydroxyapatite rings as the artificial tracheal cartilage, a carbon fiber tube as the tracheal tube; it was then implanted into the cervical trachea in dogs. Morphologic examination revealed that the hydroxyapatite ring was anchored firmly to the tracheal cartilage by ingrowth of cartilaginous tissue into the macropores of the hydroxyapatite.