Advanced Tape Research Articles

Using carbon fiber tape to tailor the coefficient of thermal expansion in 3D-Printed composite tooling

In this work, we investigated the effect of plain woven carbon fiber tape embedded in each layer of an additively manufactured part on the coefficient of thermal expansion (CTE) and compared it to conventionally printed parts. Current advancements in Additive Manufacturing enable cost-efficient 3D printing of composite tools. However, these tools do not yet offer a low CTE comparable to Invar, necessary for producing aerospace-quality composite parts. Using the novel Advanced Tape Layer Additive Manufacturing process, the tape is placed on top of the bead immediately after extruding the short fiber-reinforced material. The samples are compared to Material Extrusion specimens from a Large Format Additive Manufacturing System. A lower CTE was achieved within the printing plane. Micro-computed tomography images correlate the preferential orientation of short fibers with measured CTE values. The CTE modification can match the part CTE to the tool CTE and therefore optimize the quality of manufactured parts.

Tripling thermoplastic adhesive tape shear fatigue lifetime by decorating the adhesive–carrier interface with tailored sacrificial defects

Thermoplastic adhesive tapes are widely used in nonstructural applications such as automotive and medical industries, where fast bonding is needed with relatively good adhesion. In medical applications, the possibility of modifying the adhesive or carrier materials to adjust the toughness of the tape is very limited because of bio–compatibility constraints. In this work, the properties of the adhesive joints are enhanced without changing either the adhesive or carrier materials but by only decorating the adhesive– carrier interface with tailored defects, where the toughness and strength can be tailored depending on the size, distribution and fractional area of defects. The results show that the advanced tapes can sustain up to 83 % and 210 % larger lap-shear strength and fail-ure initiation strain, respectively, compared to conventional tapes. This improvement is attributed to the ability of the defects to redistribute the stresses at the adhesive–carrier interface during loading than localizing them at the adhesive–substrate interface, which happens in the case of conventional tapes. This delays the damage initiation. Even after damage is initiated at the edges of the adhesive–substrate interface, formation of adhe-sive ligaments starts, that sustain the load and delay the final failure. Furthermore, the proposed advanced tape has a fatigue lifetime of more than three times longer than that of conventional tapes, which is promising for enhancing the treatment of human joints.

Experimental characterisation of large in-plane shear behaviour of unidirectional carbon fibre/epoxy prepreg tapes for continuous tow shearing (CTS) process

The continuous tow shearing (CTS) process is an advanced tape placement technique with the ability to steer unidirectional prepreg tapes by in-plane shear deformation without the presence of tape buckling, gaps and overlaps. However, the inherent fibre misalignment within the tape can induce fibre waviness during the shearing process, which is further affected by processing parameters such as temperature, shear rate and fibre tension. In this paper, the effect of those parameters on the shear behaviour of two different unidirectional carbon/epoxy prepreg tapes was experimentally investigated. A bespoke test fixture was designed to shear the tape specimens at various shear rates and fibre tensions. Digital image correlation (DIC) was used to obtain full-field strains of the specimens to investigate the fibre realignment during shearing. Experimental results showed that both temperature and fibre tension significantly affect the uniformity of the fibre realignment. Moreover, the responses of the two prepreg tapes under the same shearing condition were different due to their different impregnation characteristics.

Some Results of the EU Project FASTGRID

The EU FASTGRID project aimed at improving the REBCO conductor in order to enhance its economical attractiveness for the Superconducting Fault Current Limiter (SFCL). Two approaches were simultaneously investigated: i) the reduction of the tape length through the increase of the electric field during limitation, ii) the reduction of the tape cost through improved yield and higher critical current, including the lowering of the liquid nitrogen bath temperature to 65 K. We carried out a base line using an upgraded THEVA tape. Different approaches have been tried to improve the shunt layer, both with metallic and non-conductive materials. As a first solution, we developed and successfully tested a conductor with a Hastelloy shunt able to withstand 130 Vrms/m during 50 ms at 65 K and low prospective current faults. This conductor was used in two pancake coils. These have been successfully tested at IPH in Berlin. The second shunt solution developed consisted of a ceramic in epoxy matrix coating. Another significant improvement of the tape is the successful implementation of the Current Flow Diverter (CFD) concept with a simple sulfidation process or a deposition of an insulating yttria nanolayer by Inkjet Printing. An increase by one order of magnitude of the Normal Zone Propagation Velocity with respect to tapes without CFD has been measured. A low cost and fast hot spot detection system has also been developed. To reach much higher electric fields under limitation, the FASTGRID team also developed advanced tapes based on a sapphire substrate, which can tolerate ultra-high electric fields up to about 1 kV/m. Validated at laboratory scale, this game-changing technology needs to be implemented in long lengths with an industrial process. One pancake was integrated and tested with a low-cost optical fiber and fast hot spot detection system, developed and patented within the FASTGRID project. This manuscript will showcase most of these FASTGRID results.

Buckling and strength analysis of panels with discrete stiffness tailoring

Continuous variation of stiffness across flat plates has been shown, theoretically, to improve buckling performance by up to 60%. However, steered fibre manufacturing methods cannot achieve the minimum radius of curvature required for improvement whilst maintaining a high deposition rate. An alternative concept, Discrete Stiffness Tailoring (DST), which varies stiffness within a ply through discrete changes of angle, is compatible with high rate deposition methods such as Advanced Tape Laying. Through the simple example of redistribution of the material in a quasi-isotropic [±45/90/0]2S laminate whilst maintaining ply percentages, DST is shown both experimentally and theoretically to improve buckling stress by at least 15% with no indication of failure in regions of discrete angle change (seams). However, the reduced tensile strength of seams obtained by virtual and experimental testing means that increased buckling performance in the principle load direction needs to be balanced against loss of transverse strength.

Feedback control of transport systems in tape drives without tension transducers

Accurate control of tape tension and velocity will be required in advanced tape drives, as tape thickness is reduced and track density is increased towards target tape capacities of 100 TB and beyond. In this paper, a novel method is introduced for the feedback control of the tape transport in tape drives without tension transducers. The method relies on estimating tape tension variations from the difference of the measured lateral positions of servo read elements on adjacent servo bands. Furthermore, a technique for the suppression of periodic tape tension disturbances, which are caused by reel eccentricities and other once-around effects, is developed and presented. The technique uses a time-varying narrow-band bi-quad filter with variable center frequency to suppress the slowly time-varying disturbances. To avoid the noise enhancement that would occur when the disturbance frequency moves outside of the loop bandwidth, the filter parameters are determined by H∞-norm minimization. Using the proposed tape transport system, we experimentally demonstrate a reduction in the standard deviation of the tension of about 40% and a reduction in the standard deviation of the velocity of about 23% with respect to state-of-the-art tape drives.

Characteristics of Each Bonded Layer of a Polymer-Based Magnetic Tape Using Rule-of-Mixtures and Dynamic Mechanical Analysis

A rule-of-mixtures approach is used with dynamic mechanical analysis (DMA) to determine the viscoelastic characteristics of individual layers of a fourth-generation advanced magnetic tape used for archival storage. Such tapes are comprised of three layers: a 0.92 µm thick poly(ester-urethane)-based front coat that binds the magnetic particles together, a 5.00 µm thick poly(ethylene naphthalate) substrate, and a protective 0.64 µm thick back coat with cellulose nitrate as a constituent. The storage modulus, loss modulus, and loss tangent determined for each layer are discussed in terms of their influence on magnetic tape properties and characteristics.

Dynamic tape path alternation with novel rotary guider

To enable higher recording density and data access accuracy, controlling lateral tape motion within high precision specifications through calibrated tape tension control is one of many key focuses for extra high density magnetic tape drives. This paper presents a novel rotary actuation mechatronic system which regulates travelling tape tension in a modern tape drive by dynamically alternating its tape path through closed-loop controls. Effectiveness of the system was demonstrated through calibrated laboratory parametric studies from which variation of travelling tape tension was found to be significantly reduced. The work described herein suggests engineering feasibility of using flangeless guiders in modern advanced tape drives as well as tape tension control without regulating tape drive’s driving motors.

Adoption of single-sided adhesive tape to improve thermal-cycling reliability in plastically-encapsulated semiconductor devices

A more advanced tape structure was designed to improve the thermal-cycling reliability of the semiconductor devices packaged using the LOC die attach technique. The thermal-cycling test indicates that the replacement of the conventional DSAT by the advanced SSAT is very effective for suppressing the propagation of the pre-existing cracks induced at the device edge prior to the reliability test. This is because the complete elimination of the lower-sided adhesive layer can reduce the thermal-cycling induced stress level on the device pattern. Herein, the removal of the lower-sided adhesive layer indicates its substitution with the base layer with many through-holes, which will be infiltrated by the single-sided adhesive material due to capillary action. Thus, if a base layer having a value of CTE close to silicon is adopted, the thermal-cycling reliability of corresponding semiconductor devices will be maximized due to much reduced thermal displacement-induced stress level. Consequently, the present work suggests that the use of a single-sided adhesive tape might offer greater reliability range for the structural modification or material selection of the active pattern in plastic packages.

Every little helps

In May this year, British researchers announced a euro3m, European Union-funded project to develop 'radically innovative' electrical insulating tapes, based on nano-materials, for high-efficiency generators. Dubbed 'ANASTASIA', the 'advanced nanostructured tapes for electrotechnical high-power insulating applications' project aims to replace today's thick, semi-rigid insulating tapes with thinner, flexible version. These would have a higher field-strength and better thermal stability.

Dual Easy Axes Effect on Nanosized Near-Spherical Particles for Advanced Tape Storage

Conventional needle-shaped tape particles utilize shape anisotropy to enable magnetic storage. Developed with near-spherical shape and strong crystalline anisotropy, the nanosized composite advanced particles (NanoCAP) are one of the potential candidates for future tape data storage. However, because of the imperfect shape in fabrication, significant shape anisotropy still exists in NanoCAP, forming a second easy axis in addition to that of the crystalline anisotropy. In this paper, the effect of the dual easy axes is studied by micromagnetic modeling. The analysis shows that the parasitic shape anisotropy degrades media performance. Schemes for reducing the parasitic shape anisotropy are quantitatively evaluated.

Magnetic Tape Developments for HDV Recording with MPEG-2 Compression

Current innovations in compression technology allow for the storage of high-definition format video on the same format cassette that is used for standard definition. This is done using MPEG-2 compression. To achieve high rates of compression, MPEG-2 uses a groups of pictures (GOP) method with a single intraframe (I frame), complete picture information, predictive (P frames), and bidirectional frames (B frames) that are dependent on context to create a complete image. Bit for bit, this MPEG-2 stream puts greater demands on data transfer integrity during playback in order to decode and reconstruct each and every frame in the GOP as they were originally encoded. This requires a technologically advanced tape media. In this paper, the methods for making metal-evaporated tape media capable of meeting this need will be discussed.

Failure Mechanisms of Advanced Metal Evaporated Tape in an Advanced Linear Tape Drive

Demand for increased data storage has resulted in the development of various types of magnetic tape. To achieve higher recording density, tape manufacturers are developing thin-film tapes, such as advanced metal evaporated (AME) tape, for use in linear tape drives. The structure of AME tape is fundamentally different from metal particulate (MP) tape. The goal of this study was to determine the methods and mechanisms associated with failure of AME tapes as well as to investigate the effect of tape cupping and initial edge quality on tape durability in an advanced linear tape drive. It is shown that AME tape exhibits a slightly lower coefficient of friction than the MP. The negatively cupped AME tape demonstrated a greater value of lateral tape motion peak-to-peak amplitude than both of the positively cupped AME samples as well as the MP tape sample. It was found that poor initial tape edge condition plays a large role in debris generation. For these reasons, positively cupped AME tapes with good initial relative edge contour are recommended for use in linear tape drives. The dominant mechanism of failure for the AME samples is adhesive wear resulting in removal of the DLC overcoats and sublayers. Review led by Tom Karis

An MPEG-4-Based High-Definition Videotape Recorder

The subject of this paper is an advanced tape format designed especially for digital cinema production and post-production, ultra-high-quality shooting, and blue-and-green-screen shooting. It is also suitable for final on-air program delivery and interchange of HDTV. This paper will concentrate on the coding techniques used, the multiformat capability demanded by users, and the implementation of a format converter to allow easy integration into a multistandard world. A key development is the implementation of an MPEG-4 Studio Profile chipset With 10-bit recording at HD resolutions in either 4:2:2 (YCbCr) or full chroma bandwidth 4:4:4 (RGB) at up to 60 frames/sec, the videotape recorder (VTR) is also backwards-compatible with the two most widely used tape formats in the HD and SD world. The packing density on tape is well over 300 Mbits/sq. in., nearly five times that of the Type D6 format, and a portable version, which can record at double the net video data rate. That is 880 Mbits/sec, allowing a full 444 (RGB) recording at only 2:1 compression. This format has been proposed to SMPTE for standardization.

Effect of temperature, humidity and crystal directions on wear of rotary heads

In the advanced tape drive systems which achieve a higher recording density, the wear of rotary heads should be decreased to obtain a higher reproduced output signal by decreasing the ‘Gap depth’ of heads, keeping enough life time. By using the heads made by two kinds of crystal directions of Mn–Zn ferrite and metal evaporated tapes with DLC coating, temperature and humidity dependences of head wear are investigated. The wear rates of both crystal direction heads increase with the decrease in temperature. The wear rate of a (110) head increases very quickly at low temperature, compared with a (100) head. These temperature dependences of head wear are caused by the temperature dependence of the elastic modulus of the tape and the temperature dependence of the friction coefficient between the tape and the head.

Spatial effects in the dc modulation noise of advanced MP tape

An experimental study of dc modulation noise as a function of the remanent magnetized state has been made for a set of advanced metal particle tapes with identical particles but different magnetic coating thickness between 150 and 300 nm. The thickest tape showed noise characteristics similar to conventional thick tapes, whilst the noise spectrum of the thinnest was "thin-film" like. A simulation of a magnetic recording head-read process has been developed and applied to a model of particulate recording media. This showed that particles at the surface contribute noise characteristics similar with those of thin films, whereas noise from particles in the bulk is characteristic of thick media. As tapes get thinner, the noise is dominated by the characteristics of the particles on the top surface.

Experimental analysis of tape noise

The mechanism of the tape medium noise is investigated by comparing the magnetization fluctuation resulting from an incremental DC erase process. It is found that the produced magnetization fluctuation displays contrasting behavior for recording heads with two very different gap lengths. A quantitative analysis of the medium noise mechanisms indicates that the sensitivity of the record head to spacing fluctuations explains these differences, and it is concluded that the main mechanism of the medium noise in advanced tape media is the head medium spacing fluctuation due to surface roughness.

Quantifying advanced tape medium noise

An investigation of the tape medium noise mechanism analyzed the magnetization fluctuation produced by an incremental dc erase process in a variety of modern metal-particle tape media. It examined the wavelength characteristics of the noise and compared the integrated noise during the reverse dc erase process with in situ remanent hysteresis curves. The integrated noise power followed the square of the first field derivative of the remanent hysteresis curve, (dM/dH)/sup 2/, showing that spatial fluctuation of the recording field inside the medium is a major source of the tape medium noise. It excluded spatial fluctuation of the medium coercivity as a possible noise source by comparing results from recording heads with two very different gap lengths. A quantitative analysis of the medium noise spectra at different erase currents indicated that interfacial roughness at the magnetic coating backside in some dual-layer media is a major source of medium noise. The conclusion: The main mechanism of the medium noise in advanced tape media is the head medium spacing fluctuation due to surface roughness.

Performance of advanced tapes with DigaMax TM thin film heads

DigaMax TM thin film heads have been used with advanced tapes to estimate the performance improvement that is possible with respect to Co– γFe 2O 3 900 Oe coercivity tape. The use of high sensitivity magneto-resistive read heads allows signal and media noise measurements at relatively low tape speeds with minimal interference from the electronics noise. This measurement method shows that although the absolute signal from advanced tapes has increased tremendously in recent years, the signal-to-media noise ratio has increased at a much smaller rate. Nevertheless, the best commercial metal evaporated tape of today shows a 4–5 dB improvement in signal-to-noise ratio when compared to 900 Oe tape.

An advanced linear multi-channel tape head for digital video applications

This paper describes the design, fabrication and performance of an advanced multi-channel tape head for linear digital video applications. The heads were batch fabricated on AlTiC substrates using conventional thin film processing techniques. Each head comprised an array of 16 channels, with each channel consisting of a merged MR reader/inductive writer structure. Two separate head designs were manufactured to investigate improved areal density recording. One type had a channel pitch of 150 um and did not employ a servo scheme. The second type had a channel pitch of 112.5 um and employed a closed loop servo mechanism. After machining and assembly, fully functional heads were employed to write data onto conventional 1650 Oe metal particulate tape media using RLL (1,7) code at a track density of approximately 1350 tpi and a linear transition density of 102 kpbi resulting in an areal density of 138 Mb/in/sup 2/. The heads exhibited good output, symmetry, resolution and overwrite. The data indicates that with careful process control, it is feasible to manufacture multi-channel tape heads using thin film processing techniques.