Polymer Core Layer Research Articles

Laser Welding of Metal-Polymer-Metal Sandwich Panels

In the production of metal-polymer multilayer composite parts, e.g., for automotive applications, the possibilities of thermal joining are limited due to the instability of the polymer core at elevated temperatures. Accordingly, such materials require a special approach to their welding. The three-layered metal-polymer-metal samples were made of DPK 30/50+ZE dual-phase steel as cover sheets that were electrolytic galvanized, and a polypropylene-polyethylene foil as core material, with thicknesses of 0.48/0.3/0.48 mm. The samples were welded on both sides using a 1.06 µm Nd:YAG ROFIN StarWeld Manual Performance laser. Significant improvements of the welding conditions are achieved by machining the edges of materials to be welded. The parameters of laser welding were chosen in such a way that the polymer structure remained almost unchanged. The weld thickness was about 40% of the thickness of each steel layer. It was established that within the selected laser processing parameters the melting occurred uniformly, while the polymer layer practically did not change its structure. Therefore, it can be stated that two-sided joint welding of metal-polymer-metal composite sandwich panels, without significant degradation of the polymer core layer, is feasible.

Joining metal-polymer sandwich composite sheets with mechanical nuggets

This paper presents a new joining by forming process to produce lap joints in metal-polymer sandwich composite sheets. The process involves drilling a blind hole in each sheet for removing the upper metal skin and the polymer core layer, and fixing them together by compressing a metal insert placed in-between to obtain a form-fit mechanical nugget. The cross-section of the joint resembles that of resistance spot welding, with the cold formed insert (‘nugget’) hidden inside the sheets. The geometry and size of the inserts are analysed by finite elements and experimentation to determine the effectiveness and performance of the new joints.

Assessment of the apparent bending stiffness and damping of multilayer plates; modelling and experiment

In the context of aeronautics, automotive and construction applications, the design of light multilayer plates with optimized vibroacoustical damping and isolation performances remains a major industrial challenge and a hot topic of research. This paper focuses on the vibrational behavior of three-layered sandwich composite plates in a broad-band frequency range. Several aspects are studied through measurement techniques and analytical modelling of a steel/polymer/steel plate sandwich system. A contactless measurement of the velocity field of plates using a scanning laser vibrometer is performed, from which the equivalent single layer complex rigidity (apparent bending stiffness and apparent damping) in the mid/high frequency ranges is estimated. The results are combined with low/mid frequency estimations obtained with a high-resolution modal analysis method so that the frequency dependent equivalent Young's modulus and equivalent loss factor of the composite plate are identified for the whole [40 Hz-20 kHz] frequency band. The results are in very good agreement with an equivalent single layer analytical modelling based on wave propagation analysis (model of Guyader). The comparison with this model allows identifying the frequency dependent complex modulus of the polymer core layer through inverse resolution. Dynamical mechanical analysis measurements are also performed on the polymer layer alone and compared with the values obtained through the inverse method. Again, a good agreement between these two estimations over the broad-band frequency range demonstrates the validity of the approach.

On-chip, high-sensitivity temperature sensors based on dye-doped solid-state polymer microring lasers

We developed a chip-scale temperature sensor with a high sensitivity of 228.6 pm/°C based on a rhodamine 6G (R6G)-doped SU-8 whispering gallery mode microring laser. The optical mode was largely distributed in a polymer core layer with a 30 μm height that provided detection sensitivity, and the chemically robust fused-silica microring resonator host platform guaranteed its versatility for investigating different functional polymer materials with different refractive indices. As a proof of concept, a dye-doped hyperbranched polymer (TZ-001) microring laser-based temperature sensor was simultaneously developed on the same host wafer and characterized using a free-space optics measurement setup. Compared to TZ-001, the SU-8 polymer microring laser had a lower lasing threshold and a better photostability. The R6G-doped SU-8 polymer microring laser demonstrated greater adaptability as a high-performance temperature-sensing element. In addition to the sensitivity, the temperature resolutions for the laser-based sensors were also estimated to be 0.13 °C and 0.35 °C, respectively. The rapid and simple implementation of micrometer-sized temperature sensors that operate in the range of 31 – 43 °C enables their potential application in thermometry.

Low half-wave voltage Y-branch electro-optic polymer modulator based on side-chain polyurethane-imide

A Y-branch electro-optic (EO) polymer modulator has been designed and fabricated. High performance side-chain polyurethane-imide (PUI) with a high EO coefficient of larger than 50 pm/V and a moderate glass-transition temperature [Formula: see text] of 206[Formula: see text]C is used as EO polymer core layer of the modulator. The fabricated phase modulator exhibits a low half-wave voltage of 1.94 V at 1550 nm in single arm modulation with 1 cm EO interaction length and 2 cm total length. The results show that the modulator fabricated by side-chain PUI EO materials possesses potential applications in low driving voltage and low cost optical systems.

Compact multimode polymer optical 1 × 2 Y splitters with large core planar waveguide

Design, fabrication and properties of compact large core multimode optical polymer splitter is presented. Norland optical adhesive glue was used as waveguide core layers, poly(methyl methacrylate) was used for substrate and the fabricated planar splitter is connected by standard plastic optical fiber. The structure was designed by beam propagation method and Y-groove for the waveguide core layer into poly(methyl methacrylate) substrate was made by using CNC engraving and polymer core layer was hardened by applied UV light. The splitter has insertion loss 5.2 dB for 532.8 nm and 4.1 dB for 650 nm.

Printable thermo-optic polymer switches utilizing imprinting and ink-jet printing

We demonstrate a printable Thermo-Optic (TO) switch utilizing imprinting and ink-jet printing techniques. The material system, optical and thermal designs are discussed. Imprinting technique is used to transfer a 2 × 2 switch pattern from a flexible mold into a UV15LV polymer bottom cladding. Ink-jet printing is further used to deposit a SU-8 polymer core layer on top. Operation of the switch is experimentally demonstrated up to a frequency of 1 kHz, with switching time less than 0.5 ms. The printing technique demonstrates great potential for high throughput, roll-to-roll fabrication of low cost photonic devices.

Analysis of second harmonic generation in photonic-crystal-assisted waveguides

We study second harmonic generation in a planar dielectric waveguide having a low-index, polymer core layer, bounded by two multilayer stacks. This geometry allows exceptionally strong confinement of the light at the fundamental wavelength inside the core region with virtually zero net propagation losses for distances that exceed several centimeters, provided that material and scattering losses are neglected. A phase-matched configuration of the waveguide is reported in which the pump signal is the lowest-order mode of the waveguide, and the generated second harmonic signal corresponds to the third propagation mode of the waveguide. Using a polymer waveguide core, having χ(2)∼100pm∕V, we predict a conversion efficiency of approximately 90% after a propagation distance of 2mm, using peak pump intensities inside the core of the waveguide of 1.35GW∕cm2. If the waveguide core contains polymer layers with different glass transition temperatures, the layers can be poled independently to maximize the overlap integral, and similar pump depletions may be achieved over a distance of approximately 500μm.

Effect of conductivity and dielectric constant on the modulation voltage for optoelectronic devices based on nonlinear optical polymers

Presented is the effect of using various cladding materials with different conductivities and dielectric constants on the applied voltage for optoelectronic (OE) devices based on nonlinear optical (NLO) polymers. Using a conductive polymer, we have demonstrated a 3 to 13 times increase in the effective electro-optic (EO) coefficient of electrode- poled NLO polymers, compared to using passive polymer claddings. We have achieved the lowest poling voltage to date for maximum EO coefficient, 300 V, for a two-layer waveguide structure consisting of a 2-?m- thick NLO polymer layer and a 2-?m-thick conductive cladding layer. The dielectric constants of both the NLO polymer core and passive polymer cladding materials used for conventional polymer-based integrated optic devices are typically very similar in magnitude. This suggests that only a small fraction of the applied modulation voltage is reaching the NLO polymer core layer, requiring 4 to 5 times higher modulation voltage than the desired V?. We have demonstrated a factor-of-2 decrease in the modulation voltage using the same conductive polymer, due to its possessing a much higher dielectric constant than the core material at the modulation frequency tested. The results show promise for shorter, lower-operating-voltage devices.