High-performance Laminates Research Articles

Thermal properties and mechanical behavior of hot pressed PEEK/graphite thin film laminate composites

This work studies high-performance laminate composite materials made of graphite and poly(ether-ether-ketone) (PEEK). The main objective was to enhance graphite's inherent properties by the addition of PEEK to produce materials with improved thermal and mechanical stability for high-performance applications. The composites were fabricated using a hot press method at a temperature below 310 °C. The newly formed materials were then subjected to various tests, including Scanning Electron Microscopy, Thermogravimetric Analysis, mechanical properties tests, nanoindentation tests, and X-Ray Diffraction to assess their structural, thermal, and mechanical properties. Our findings showed a substantial interfacial interaction between PEEK and graphite, indicating successful composite formation. Both three-layered PEEK/graphite/PEEK (PGP) and five-layered PEEK/graphite/PEEK/graphite/PEEK (PG)2P composites exhibited superior thermal stability at high temperatures compared to neat PEEK. Moreover, our mechanical tests demonstrated a 172% increase in ultimate tensile strength of PGP compared to neat graphite. Additionally, nanoindentation tests confirmed an increase in both Young's modulus and hardness of composites. Furthermore, XRD analysis revealed a 35.5% increase in crystallinity in the fabricated composites compared to pristine PEEK. These findings significantly contribute to the field of high-performance composite materials, confirming that the hot pressing of PEEK and graphite sheets results in enhanced thermal and mechanical properties.

Enhanced interlayer adhesion of wetted graphene oxide by confined water bridge.

Graphene oxide (GO) sheets are widely used as building blocks in flexible electronic devices, structural materials, and energy storage technology owing to physicochemical flexibility and remarkable mechanical properties. GO exists as lamellar structures in these applications and, thus, it urges to enhance interface interaction to prevent interfacial failure. This study explores the adhesion of GO with and without intercalated water utilizing steered molecular dynamics (SMD) simulations. We find the interfacial adhesion energy (γ) depends on the synergistic effect of the types of functional groups, the degree of oxidation (c), and water content (wt). The intercalated monolayer water confined within GO flakes can improve the γ by more than 50% whereas the interlayer spacing is enlarged. The enhancement of adhesion is from the cooperative hydrogen bonding bridges between confined water and functional group on GO. Furthermore, the optimal water content wt = 20% and oxidation degree c = 20% are obtained. Our findings provide an experimentally available way to improve interlayer adhesion through molecular intercalation, which opens the possibility of high-performance laminate nanomaterial-based films for versatile applications.

Microstructure and mechanical properties of in-situ synthesized Ti(N,C) strengthen IN718/1040 steel laminate by directed energy deposition

Directed energy deposition (DED) additive manufacturing technology is used to fabricate (IN718 + Ti)/1040 laminate. It is a promising method to increase the microhardness, adjust the microhardness and improve the mechanical properties of laminates by DED. Scanning electron microscope (SEM), Energy Dispersive Spectromete (EDS) line scanning and microhardness test are used to characterize the transition zone width. In-situ synthesized ceramic strengthening phase by adding Ti powder to the depositing material improves the microhardness from and tensile strength significantly, which provides a reference for designing and fabricating new high-performance laminates.

High-performance laminate material based on polyurethane and epoxide reinforced by silica particles from rice husk used for intelligent pedestrian crossings

Intelligent pedestrian crossings were made with the aim to increase pedestrian safety at poorly lit locations. New technologies include the design of polymer materials that have high performance by optimizing properties such as compression, tensile and impact strengths, wear resistance, hardness and transparency. The desired properties are set up to face the demands of a heavy daily traffic load and enable the functionality. Laminate material consists of the epoxy composite reinforced with silica (SiO2) derived from rice husk waste and a protective thermoplastic polyurethane layer. The top layer of the laminate material is a transparent thermoplastic polyurethane (TPU) serving as a protective layer with high wear resistance and good adhesion with epoxy composite. Silica obtained from rice husk waste was used in reinforcing of the epoxide in order to improve the mechanical properties, diffuse the light, improve the adhesion with TPU and decrease the production costs. Micro-Vickers hardness of the epoxy composite was increased by 70% with the addition of 15 wt% of SiO2. Impact energy of the epoxy composite with 15 wt% of SiO2 was increased by 272.9% after adding the TPU layer. Compressive strength of the epoxy resin is improved by 16.2% by reinforcement with 15 wt% of SiO2, while the laminate composite material showed 207% higher compressive strength than the commonly used asphalt pavement. Moreover, the addition of 15 wt% of SiO2 improved the adhesion between epoxy composite and TPU layer (11.2%). Thus, obtained laminated material made of the epoxy composite with 15 wt% of SiO2 (obtained from rice husk waste) and TPU598 showed mechanical properties and LED light transmission/diffusion appropriate for application in the intelligent pedestrian crossings.

Microstructure and mechanical properties of AI/Fe micro-laminated composites fabricated by ultrasonic consolidation

Ultrasonic consolidation technology is a new method for preparing high-performance laminate composite materials. This rapid consolidation additive manufacturing technology provides a new idea for the integration of complementary functional laminated composite structures. It has great potential for preparation of new generation of complex laminated composite parts, broadening the application field of laminated composite material, and means an advanced 3D additive manufacturing technology for materials and structures. In this paper, it is aimed at Al/carbon steel and Al/Fe laminated composites systems with low cost and multilayer structures, Al/carbon steel and Al/Fe laminated composite samples were consolidated by ultrasonic consolidation process. And the Al/carbon steel and Al/Fe interfacial bonding were studied by SEM and EDS. The hardness and tensile properties of laminated composites were tested by mechanical properties together with the fracture morphology of each interface was studied.

Seismic behavior of strengthened square reinforced concrete columns under combined loadings

This paper presents an experimental study examining the seismic behavior of square reinforced concrete (RC) columns subjected to combined loadings. In this study, nine full-scale square RC columns were made with the same structural properties. Five of them were strengthened with high-performance ferrocement laminate and bonded steel plates in order to investigate the effects of strengthening on the seismic behavior of RC columns under combined loadings. Finally, the failure mode, hysteretic load-displacement response, bearing capacity, energy dissipation, ductility and plastic hinge characteristics were recorded and analyzed. The results show that combined loadings reduced the bearing capacity and changed the failure modes and deformation characteristics. Strengthened RC columns had significantly improved bearing capacity and different failure modes under the same combined loadings in contrast to the non-strengthened RC columns. The vertical eccentricity had little effect on the mechanical properties of columns, while the horizontal eccentricity significantly weakened the mechanical properties of columns. The mechanical properties of uniaxial compression-bending-shear-torsion columns were the worst. The tri-linear model calculation parameters under different failure modes and combined loadings were fixed and validated by experimental results.

CATPUAL - An Innovative and High-Performance Hybrid Laminate with Carbon Fibre-Reinforced Thermoplastic Polyurethane

In consideration of environmental aspects and limited availability of resources, the focus of automotive and aerospace industry lies on significant weight optimisations especially for moving loads. In this context, innovative lightweight materials as well as material combinations need to be developed. A considerable potential for lightweight structures can be found in fibre- or textile-reinforced semi-finished products. Due to their specific characteristics and extraordinary structural diversity, thermoset and thermoplastic matrix systems can be used. In particular, carbon fibres as reinforcing components combined with a thermoplastic matrix polymer are able to create new high-performance applications. Besides the significant lightweight characteristics of the fibre-plastic-composites, in some instances contrary requirements must be satisfied in many areas, such as strength and ductility. In this field, the combination of fibre-reinforced polymers with aluminium or titanium sheets creates unique composite materials, so called hybrid laminates, which fulfil the unusual expectations.The focus of the current study lies on the development of a new thermoplastic hybrid laminate named CATPUAL (CArbon fibre-reinforced Thermoplastic PolyUrethane/ALuminium laminate). The structure of the laminate is an alternating sequence of thin aluminium sheets (EN AW 6082-T4) and fibre-reinforced thermoplastic polyurethane (TPU). The individual layers are consolidated to each other by using a hot pressing process. First results showed that the impregnation capability of thermoplastic polyurethane surpasses any other commercially available hybrid laminates. Furthermore, the mechanical properties regarding bending strength and interlaminar shear strength are exceeding the state of the art drastically.

Calculation of Axial Compression Capacity for Square Columns Strengthened with HPFL and BSP

The load carrying capacity and failure mechanism of 8 square columns strengthened with high-performance ferrocement laminate (HPFL) and bonded steel plates (BSP) were analyzed on the basis of experiments on the axial compression performance of these columns. Results show that the reinforcing layer worked together with the original columns as a whole, and the load-bearing capacity significantly increased. When failure of the strengthened column occurred, the mortar and concrete were crushed and bulged outward in the middle of the columns, the angle bars and longitudinal steel bars buckled, and some stirrups were pulled out. The chamfering of angle bar momentously affected the primary damage of steel strand. The values of the strength reduction factor and pressure effective utilization coefficient of the mortar were suggested. Based on the experiments and existing tests of 35 columns strengthened with HPFL, equations for the axial compression bearing capacity were proposed and all calculation results agreed well with testing results. Therefore, the calculation method could be used in the capacity design of axial compression strengthened columns.

Permeation of water vapor through high performance laminates for VIPs and physical characterization of sorption and diffusion phenomena

Maintaining the long term performance of vacuum insulation panels (VIPs) remains the focus of many technical and scientific investigations. The performance of the barrier laminate is decisive to hold the vacuum level and to resist the permeation of water vapor. This barrier property against water vapor is characterized by the permeance of the laminate. The permeance of several commercially available products was determined by different methods and a good correlation was obtained between the manometric method on laminates and the current reference method on VIPs (weight gain in climatic chambers).Even if the permeance is appropriate to evaluate the performance of VIPs under stationary conditions, the solubility and diffusion coefficients are required for a fine-tuned service life prediction under real climatic loading conditions. Whereas for the PET the absorption isotherm is linear up to high humidity levels, this is not the case for the sealing layers, nor for the laminates. But this deviation from Henry's law does not impact the modeling of the behavior of current laminates because only the external PET layer is exposed to high humidity. The activation energies of sorption and diffusion have been evaluated. The experimental results on metalized and non metalized PET films confirm that the temperature dependence of the diffusion and of the permeance is driven by the behavior of the polymer.

Heterogeneous Solution Deposition of High-Performance Adhesive Hybrid Films

Interfaces between organic and inorganic materials are of critical importance to the lifetime of devices found in microelectronic chips, organic electronics, photovoltaics, and high-performance laminates. Hybrid organic/inorganic materials synthesized through sol-gel processing are best suited to address these challenges because of the intimate mixing of both components. We demonstrate that deposition from heterogeneous sol-gel solutions leads to the unique nanolength-scale control of the through-thickness film composition and therefore the independent optimization of both the bulk and interfacial film properties. Consequently, an outstanding 3-fold improvement in the adhesive/cohesive properties of these hybrid films can be obtained from otherwise identical precursors.

Manufacturing process and performance of dry carbon fabrics reinforced with rectangular and circular z-pins

Composite materials possess high mechanical in-plane properties but suffer from very low out-of-plane properties due to limited inter-laminar strength. Common z-pinning techniques to improve the mechanical properties of composites materials are presented in this paper. Special techniques to reinforce liquid composite molding preforms are explained. A new, low-cost z-pinning method to create high-performance laminates of dry fabrics invented by the author will also be introduced. Mode I double cantilever beam tests are performed to compare rectangular and circular z-pins using the newly described manufacturing process.

Study on Tear Propagation of a Fabric Laminate in Biaxial Stress

Tear propagation is the typical fracture mode of fabric laminates, which is affected by stress and damage size. With the use of high strength fabrics, high performance laminates emerge continually. In this paper, tear propagation of a high strength fabric laminate coating polyurethane used in high altitude lighter-than-air vehicle (LTA) is studied. Cross-shaped specimens, central size 5cm×5cm, are scissored out to test tear propagation strength in biaxial stress by a tailor-made testing machine. The damnification is a cut slit in weft direction, warp fibers cut off. The cut slit is in the middle of specimens, including 0cm (scatheless specimens), 1cm, 2cm and 3cm in length. Tear propagation is observed and the strength is noted simultaneously to gain the mechanical properties of the fabric laminate. The tensile strength of the laminate is 424N/cm, and it descends to 263N/cm in cut slit length of 1cm. Subsequently, two methods based on stress field and linear elasticity fracture mechanics are introduced to analyze the tear strength, which is validated well by test results, and the coefficients of empirical formulae are obtained. It is useful to analyze the limit length and the limit stress for the fabric laminate with initial damage.

Calculation of diagonal section and cross-section bending capacity for strengthening RC structure using high-performance ferrocement laminate

Because there is a great demand of reinforcement and retrofitting of aged structures nationwide, as well as the rapid development of innovative building materials, the adoption of strengthening RC structures using new inorganic materials has become possible. High-performance ferrocement laminate (HPFL) is an effective method of strengthening concrete structure. High-performance ferrocement laminate is a new type of inorganic material with the advantages such as high strength, small contraction, good bonding properties, etc. This paper introduces the formula of cross-section bending capacity for strengthening concrete beams with HPEL. A comparative analysis of experimental data, as well as the calculation of diagonal section bearing capacity of concrete members, is given.

Experiences with peel strength

PurposePeel strength numbers are part of a laminate's specifications and should characterize the specific bond performance (copper adhesion) under test conditions. Unfortunately, from both a theoretical and a practical point of view they are not able to do that. This study seeks to address this issue.Design/methodology/approachThis paper has been written to show the main impacts on the measured peel strength numbers in the IPC‐TM‐650 peeling test. From an extensive database regarding peel numbers for diverse foil types, foil thicknesses and treatment roughnesses it is possible to show the influence of prepreg type, foil thickness and roughness on the measure peel strength.FindingsCopper adhesion to laminating resin is insufficiently described by peel strength data because of the impacts of foil thickness, stiffness on bending (physical bending work, stress distribution underneath the peeling line) and the treatment roughness. The latter works reinforcing regarding the (low) resin strength and this influence is measured on resin strength instead of real bond. Fracture due to peeling is cohesive, mostly with a totally intact copper‐resin interface. This is especially true in high performance laminates that show low peel strengths not because of bad copper bonding but because of brittle resins (filled and unfilled).Originality/valueUsers have to understand the limited benefit of the IPC peel test in characterizing copper‐resin bonds. Peel increase on (low bond) high performance resins by increased foil roughness is not a practical way in the field because of no bond improvement (interface) and heavy disadvantages in dielectric thickness (HiPot tests at thin core laminates), respectively.

Delamination of Z-pinned carbon fibre reinforced laminates

The paper outlines the current status of mechanical testing, identification of failure mechanisms and data analysis related to delamination cracking in high performance laminates made via the prepreg/autoclave route, strengthened in the through-thickness direction by Z-pinning. The applied loading cases under consideration are limited to Mode I and Mode II. Sample preparation, test methodologies and applicability of data reduction schemes are considered, with data obtained from within the range of aerospace and Formula 1 grades of carbon fibre/epoxy composites. Micromechanisms of failure in the three dimensional tests specimens are shown to be dependent on the architecture of the fibre reinforcement (i.e., unidirectional versus woven fabric prepregs), particularly in the case of Mode II loading.

An introduction to high performance laminates and the importance of using optimised chemical processes in PCB fabrication

With the ever increasing demands for high performance electronic devices there is a need for circuit board laminates that have enhanced properties when compared to conventional materials such as the widely used epoxide‐based FR4 laminates. Equipment manufacturers require boards with better mechanical stability and improved electrical characteristics. At the same time, new environmental legislation is set to drive electronics assembly temperatures much higher as manufacturers start to use lead‐free soldering processes. The legislation is also raising questions about the long‐term viability of brominated resins as the basis for imparting flame retardancy to laminates. Fortunately, laminate manufacturers have responded to these challenges by developing and introducing a wide range of new laminates that address these issues. This paper describes some of these challenges and gives an introduction to the new high performance laminates that are finding increasing use. It also highlights the need for chemical processes used in the manufacture of interconnects with laminates to be specifically optimised for the chosen substrate material.

High-performance laminates through chemical welding of thin liquid crystalline polymer films

A systematic study of the welding (healing) process of polymers with different chemical compositions, structures and properties was carried out. It was shown that welding can be due to a number of physical and/or chemical factors. Diffusion alone led to a relatively weak welding under the selected conditions. A jump was observed in the temperature dependence of the shear stress of polyimides. The abrupt increase in the activation energy of welding can be explained by assuming a change in the nature of the created bonds from physical to chemical ones. For the first time the chemical reactions taking place at the contacting surfaces were directly experimentally proved by electron spin resonance. In some cases, for the first time, the healing process was carried out at temperatures below the glass transition temperature. In this way, the contribution of the diffusion process to the healing may be distinguished from that of the chemical reactions. On the basis of a poly(ethylene terephthalate) copolyester containing 60 mol% p-hydroxybenzoic acid thin liquid crystalline films (160 µm thick) are obtained by melting the polymer at 300°C and chilling at 0°C. The undrawn films have a high degree of orientation as shown by X-ray measurements. These films have excellent mechanical properties because of the molecular orientation. In order to avoid losses in the mechanical strength due to increase in their thickness, laminates were prepared using thin liquid crystalline films. Lamination was carried out by annealing under pressure at 170°C for 6 hr, resulting in samples with excellent mechanical properties regardless of their thickness. A method is proposed that makes it possible to combine the unique mechanical properties of thin films of liquid crystalline polymers with a lamination process in order to obtain thick and very strong materials. Copyright © 1999 John Wiley & Sons, Ltd.

High Performance Laminate Systems for High Speed Electronics Applications

This paper reviews some of the technology trends making it necessary to take the performance of laminate materials into account when designing and fabricating high speed PWBs. It also reviews the available materials for current matched impedance circuitry and discusses the various combinations of polymer resins and reinforcements used in these applications. Additionally, it provides a look at the new materials technologies being applied to high speed applications and what candidates hold most promise for achieving greater signal speeds via lowered dielectric constant while maintaining the compatibility with existing fabrication processes.

Norplex/Oak (UK) Technical Seminar — High Performance Materials

Conference presentations, the technical literature and industry debate are focusing increasingly on the requirement for high performance laminates to meet the needs of high signal speeds, reduced dielectric constant, controlled impedance, tighter tolerances and improved dimensional stability.

Simple design for reliable high-performance laminates

A simple design for laminates is described, based on the assumptions that only axially aligned plies can sustain any load and that all applied shears can be carried as tension and compression forces at 45° to the shear axes. Classical fully-elastic design is outlined and compared with the principle of simple design. An easily applied approximation for fully-elastic design is also demonstrated. The principles and applications of this simple method are discussed. It is recommended for general use because it is conservative and easily understood and therefore more likely to be correctly applied.