Use Of Adhesive Layers Research Articles

Surface microstructuring by Ultrasonic Vibration Assisted Deformational Machining (UVADM) – Simulation and experimental results

Polymer-metal hybrids are a lightweight solution for many industrial applications, especially in the automotive or aircraft sector. However, due to their poor chemical bonding the manufacturing of such compounds requires the use of adhesive layers or the conditioning of the metallic surface to achieve form closure and high joint strength. Ultrasonic Vibration Assisted Deformational Machining (UVADM) is a novel process that generates functional microstructures with high production rates, aiming to form defined burr structures with undercuts, that have a significant impact on the interlaminar strength of polymer-metal hybrids (PMH). A 3D FEM simulation using Abaqus/Explicit software was applied to design and analyze process conditions including tool geometry. Material deformation was described by the Johnson-Cook model. Simulation results were validated experimentally using two different MCD tools. For the UVADM experiments, specimens of the aluminum alloy EN AW-6082 were used. In the tests, a constant ultrasonic frequency (20.42 kHz), machining speed (100 m/min and 200 m/min), and peak-to-peak amplitude (7 µm) were used. Geometrical surface properties were analyzed by optical methods and SEM. The study demonstrates a conformity between simulated and experimental results, highlighting the potential of UVADM for an increased productivity in the surface conditioning for polymer-metal hybrids.

Adhesion of HIPIMS-Deposited Gold to a Polyimide Substrate

Gold is the preferred material for conductive structures in neural implants. The hitherto employed process applies adhesive layers to avoid delamination of gold structures from a polymeric substrate. The possibility to deposit gold without the use of adhesive layers is offered by the high-power impulse magnetron sputtering (HIPIMS) process. In this work, it is shown that it is possible to utilize the HIPIMS process to deposit gold onto polyimide while having enough adhesion between these two layers to omit the use of an adhesive layer. A scratch test was performed to demonstrate the adherence between the layers.

One-Shot Drilling Analysis of Stack CFRP/UNS A92024 Bonding by Adhesive.

The use of adhesive layers can improve the properties and reduce the defects produced in the interfaces. This provides adherence to the structure, adapting the joining surfaces and avoiding spaces between the layers. However, the presence of the adhesive can potentiate the defects caused during drilling. In turn, a loss of adhesive in the interface can occur during machining affecting the final structure. This work has followed a conventional OSD strategy in CFRP and UNS A92024 aluminium sheet stacking with adhesive. A series of dry drilling tests have been developed with different cutting conditions and new noncoated WC-Co helical cutting tools. Analysis of Variance (ANOVA) statistical analyses and surface response models have been applied to determine the mechanical behaviour in the holes. For this purpose, the dimensional deviation, surface quality, and adhesive loss in the interface in relation to the number of holes have been considered. A combination of cutting parameters that minimizes the evaluated defects has been found. Diametric deviations and surface qualities below 2% and 3.5 µm have been measured in the materials that make up the stack with cutting speeds higher than 140 m/min and feed rates between 200 and 250 mm/min. However, the greatest adhesive losses occur at high cutting speeds.

Micro-masonry for 3D additive micromanufacturing.

Transfer printing is a method to transfer solid micro/nanoscale materials (herein called 'inks') from a substrate where they are generated to a different substrate by utilizing elastomeric stamps. Transfer printing enables the integration of heterogeneous materials to fabricate unexampled structures or functional systems that are found in recent advanced devices such as flexible and stretchable solar cells and LED arrays. While transfer printing exhibits unique features in material assembly capability, the use of adhesive layers or the surface modification such as deposition of self-assembled monolayer (SAM) on substrates for enhancing printing processes hinders its wide adaptation in microassembly of microelectromechanical system (MEMS) structures and devices. To overcome this shortcoming, we developed an advanced mode of transfer printing which deterministically assembles individual microscale objects solely through controlling surface contact area without any surface alteration. The absence of an adhesive layer or other modification and the subsequent material bonding processes ensure not only mechanical bonding, but also thermal and electrical connection between assembled materials, which further opens various applications in adaptation in building unusual MEMS devices.

DBD plasma improved spot repair of automotive polymer surfaces

Plasma activation effects on automotive polymers by low temperature plasma at atmospheric pressure have been studied. The aim of this work was the improvement of the polymer surface polarity in order to replace the use of adhesive layers before application of lacquering. Two different concepts of dielectric barrier discharge, direct and indirect plasma treatment, were applied. The efficiency of such plasma treatment was determined by adhesive pull strength tests and surface energy calculations. It was shown that both plasma treatment methods allow a significant increase in surface polarity up to a factor of 20 and adhesive pull strength of lacquers up to a factor of 29 respectively. In comparison to indirect surface treatment, the direct treatment features a higher efficiency in terms of increasing both, polarity and adhesive pull strength.

(Invited) Wafer Bonding: A Retrospective

Wafer bonding has become well-known and widely used as the process of adhesion of two flat mirror-polished wafers without the use of any intermediate adhesive layer. Today, it is used as a versatile tool in a wide variety of scientific fields and the technique has reach industrial maturity in particular for the manufacturing of Silicon-On-Insulator (SOI) materials, but also in other fields, such as for sensors, microsystems, optics and photonics. The early development of wafer bonding is reviewed and a retrospective view is taken on wafer bonding, addressing some of the critical research achievements and breakthroughs over the last three decades. The focus is limited to wafer bonding without the use of adhesive layers or electrostatic fields, and will hence not discuss related techniques, such as anodic bonding.

Optimal Use of Adhesive Layers in Reducing Impact Damage in Composite Laminates

Impact experiments were conducted on a group of cross-ply graphite/ epoxy laminates with and without adhesive layers. Impact-damage modes were examined by sectioning the impacted specimens and examining the sections with optical microscope. The effectiveness of using adhesive layers to suppress impact-induced delamination was investigated. It was found that the presence of adhesive layers could toughen the interface between two laminas and also reduce matrix cracking. A guide to optimal use of adhesive layers for improving impact resistance properties was proposed.

On the Effect of Matrix Cracks on Laminate Strength

Matrix cracks and their effect on ultimate laminate strength in [0/90]s type graphite/epoxy laminates were investigated. Crack saturation density was found ex perimentally and compared with that predicted using a finite element analysis. Good agreement was found. To estimate the effect of the 90°-ply cracks on the load capacity of adjacent 0°-plies, a soft but tough adhesive film was placed along the interfaces in some laminates to isolate the effect of the matrix cracks. The use of adhesive layers in [0/908/0] and [904/02/904] laminates raised the laminate strengths by about 30%.