Elastomeric Joint Research Articles

Compliance-Based Determination of Fatigue Design Curves for Elastomeric Adhesive Joints

A compliance-based method for the determination of fatigue design curves for elastomeric adhesive joints is developed and validated. Fatigue experiments are conducted on elastomeric adhesives (a polyurethane and a silane-modified polymer) under different stress ratios (R = 0.1/0.5/−1) and conditions (23 °C/50% r.h. and 40 °C/60% r.h.). The investigation focused on butt and thick adherent shear test joints. Fatigue tests are recorded with cameras to identify the stages of crack initiation and propagation. For each fatigue test, the stiffness and compliance per cycle are calculated until final failure. The proposed method identifies a transition point that distinguishes regions under stable and unstable compliance growth. Fatigue design curves are then built based on the transition point and on the number of cycles to reach different degrees of initial stiffness (90%, 80%, 70% and 60%). The failure ratio, i.e., the lifetime for reaching a given approach divided by the total lifetime, is introduced to evaluate the data in terms of average values and standard deviation. The results indicate that the proposed method can yield fatigue design curves with a high coefficient of determination (accuracy) and high failure ratio (avoiding over-conservative design). Moreover, the method is robust, as the failure ratio for different adhesives, stress ratios, conditions and geometries is highly consistent.

Experimental and numerical investigation of energy dissipation in elastomeric rotational joint under harmonic loading

This paper focuses on energy losses caused by inner damping and friction in an elastomeric rotational joint. A description of the design of a new experimental device intended to characterize dynamic stiffness in rotational elastomeric joint is presented. An original method based on Lagrange’s equations, which allows accurately measuring forces and torques only with accelerometers, is proposed in order to identify dissipated energy in the rotational elastomeric joint. A rheological model developed taking into account dependence of the torque and the angular displacement (rotation). Experimental results and simulations used to quantify the dissipated energy in order to evaluate the damping ratio are presented and discussed.

Photo-patternable and transparent films using cellulose nanofibers for stretchable origami electronics

Substantial progress in flexible or stretchable electronics over the past decade has extensively impacted various technologies such as wearable devices, displays and automotive electronics for smart cars. An important challenge is the reliability of these deformable devices under thermal stress. Different coefficients of thermal expansion (CTE) between plastic substrates and the device components, which include multiple inorganic layers of metals or ceramics, induce thermal stress in the devices during fabrication processes or long-term operations with repetitions of thermal cyclic loading–unloading, leading to device failure and reliability degradation. Here, we report an unconventional approach to form photo-patternable, transparent cellulose nanofiber (CNF) hybrid films as flexible and stretchable substrates to improve device reliability using simultaneous electrospinning and spraying. The electrospun polymeric backbones and sprayed CNF fillers enable the resulting hybrid structure to be photolithographically patternable as a negative photoresist and thermally and mechanically stable, presenting outstanding optical transparency and low CTE. We also formed stretchable origami substrates using the CNF hybrid that are composed of rigid support fixtures and elastomeric joints, exploiting the photo-patternability. A demonstration of transparent organic light-emitting diodes and touchscreen panels on the hybrid film suggests its potential for use in next-generation electronics. A substrate containing transparent nanofibres makes it easier for flexible electronic devices to combat the effects of thermal stress. Plastic substrates respond differently to hot and cold conditions than inorganic circuits do, and this mismatch often leads to premature failure of stretchable devices. Jang-Ung Park and co-workers in South Korea developed an alternative substrate by electrospinning a three-dimensional web of epoxy fibres while simultaneously spraying cellulose-based nanofibres into the polymer's pores. The nanofibre—epoxy hybrid substrate had a significantly lower thermal coefficient of expansion and an improved mechanical stability, and it was compatible with photolithographic patterning. The team demonstrated the potential of this approach with three prototypes: a flexible touch-screen panel, a transparent organic light-emitting diode, and ‘origami’-type substrates that can be reversibly folded and formed into arbitrary shapes. Photo-patternable and transparent cellulose hybrid films as flexible and stretchable substrates exhibit outstanding mechanical, optical and thermal properties. Exploiting the photo-patternability of the hybrid film, reversibly foldable and stretchable forms of the substrate can be produced by integrating patterns of this hybrid film with elastomeric joints. Flexible touchscreen panels and transparent organic light-emitting diodes using hybrid films are demonstrated.

Fully-integrated, bezel-less transistor arrays using reversibly foldable interconnects and stretchable origami substrates.

Here we demonstrate fully-integrated, bezel-less transistor arrays using stretchable origami substrates and foldable conducting interconnects. Reversible folding of these arrays is enabled by origami substrates which are composed of rigid support fixtures and foldable elastic joints. In addition, hybrid structures of thin metal films and metallic nanowires worked as foldable interconnects which are located on the elastomeric joints.

Variability analysis of vibrational responses in a passenger car considering the uncertainties of elastomers

Passenger cars have many elastomeric joints that are used to reduce the vibration transmission from the source to the cabin structure. In the design stage, the dynamic characteristics of the elastomeric joints are optimally determined in order to satisfy the design goals for interior noise and vibration. However, the material properties of the elastomeric joints have large variations due to production variability. In addition, operational conditions, e.g. environmental temperature, vary according to the locations of the car. As a result, the vibrational comfort of a passenger car exhibits large variations. In this paper, the amount of vibration fluctuation due to uncertain elastomeric joint parameters is estimated using a statistical approach. First, the dynamic characteristics of the elastomers are described using the fractional derivative model. The uncertainties of the fractional derivative model parameters of the elastomers are characterized using a statistical calibration approach based on specimen test data. Then, a finite element model for the elastomers and the passenger car structure are constructed in order to calculate the vibrational response. In order to estimate the variability of the vibrational response due to the uncertainties of the elastomers, uncertainty propagation analyses are conducted using the eigenvector dimension reduction (EDR) method. The operational conditions such as temperature are also included in the variability analysis. The performance of the EDR method is assessed through comparing the estimated response distribution with that of the Monte Carlo simulation (MCS) method in a simplified structure. The variability analysis results demonstrate that the vibrational response variation due to the uncertainties of the elastomers can be efficiently predicted using the proposed method. The proposed variability analysis procedure could be an effective tool in the design stage for quality control of passenger car comfort.

A Tip-Tilt-Piston Micromirror With an Elastomeric Universal Joint Fabricated via Micromasonry

A hybrid tip-tilt-piston micromirror driven by electrostatic actuation is presented in this letter. The micromirror involves a highly doped silicon mirror and a conductive elastomeric universal joint, which are mechanically bonded and electrically interconnected. This device takes advantage of two distinct materials to achieve a high-quality reflective surface using single-crystal silicon and a highly flexible universal joint using an elastomer. To realize this hybrid system, micromasonry techniques are employed such that silicon and elastomer parts are fabricated separately and integrated afterward. The static and dynamic behaviors of the micromirror are characterized, indicating identical response about its two orthogonal scanning axes. Furthermore, the piston stroke by the compressive deformation of the elastomeric joint along z-axis is investigated.

Characterization and Modeling of Elastomeric Joints in Miniature Compliant Mechanisms

Accurate analysis models are critical for effectively utilizing elastomeric joints in miniature compliant mechanisms. This paper presents work toward the characterization and modeling of miniature elastomeric hinges. Characterization was carried out in the form of several experimental bending tests and tension tests on representative hinges in five different configurations. The modeling portion is achieved using a planar pseudo rigid body (PRB) analytical model for these hinges. A simplified planar 3-spring PRB analytical model was developed, consisting of a torsional spring, an axial spring, and another torsional spring in series. These analytical models enable the efficient exploration of large design spaces. The analytical model has been verified to within an accuracy of 3% error in pure bending, and 7% in pure tension, when compared to finite element analysis (FEA) models. Using this analytical model, a complete mechanism—a robotic leg consisting of four rigid links and four compliant hinges—has been analyzed and compared to a corresponding FEA model and a fabricated mechanism.

Identification of dynamic stiffness matrices of elastomeric joints using direct and inverse methods

New experiments are designed to permit direct comparison between direct and inverse identification methods of the dynamic stiffness matrices of elastomeric joints, including non-diagonal terms. The joints are constructed with combinations of inclined elastomeric cylinders to control non-diagonal terms in the stiffness matrix. The inverse experiment consists of an elastic metal beam end-supported by elastomeric joints coupling the in-plane transverse and longitudinal beam motion. A prior method is extended to identify the joint dynamic stiffness matrices of dimension 3 from limited modal measurements of the beam. The dynamic stiffness and loss factors of the elastomeric cylinders are directly measured in a commercial elastomer test machine in shear, compression, and inclined configurations and a coordinate transformation is used to estimate the kinematic non-diagonal stiffness terms. Agreement is found for both dynamic stiffness and loss factors between the direct and inverse methods at small displacements. Further, the identified joint properties are employed in a model that successfully predicts the modal parameters and accelerance spectra of the inverse experiment. This article provides valuable insight on the difficulties encountered when comparing system and elastomeric component test results.

Evaluation of the Durability Potential of Silyl Terminated Polyacrylate Based Construction Sealant

Abstract In this paper, we discuss the durability potential of silyl terminated polyacrylate based construction sealants. The durability and performance of a silyl terminated polyacrylate (STPA) based construction sealant have been evaluated in comparison to a typical silyl terminated polyether (STPE) and a silicone sealant in order to demonstrate the potential of the STPA sealant as a high durability, high performance construction sealant that is also suitable for glazing applications. The polyacrylate backbone of STPA polymer has higher durability, especially UV stability and heat resistance, than the polyether one of STPE polymer as shown by accelerated weathering tests using carbon-arc or superhigh irradiance xenon-light sources. Adhesion of the STPA sealant on glass was retained even after 10,000 h exposure to superhigh irradiance xenon-light [180 W/m2 (300–400 nm)]. The performance of the STPA based sealant has been compared to that of the STPE based sealant by testing according to several industrial International Organization for Standardization (ISO) and Japanese Industrial Standard (JIS) standards. The STPA based sealant conforms to a higher durability class specification than the STPE sealant, for example, the requirements of class 10030 are passed with the STPA sealant, while the STPE sealant passes only class 9030 as stipulated in JIS A 5758. Furthermore, a cyclic movement test of the STPA based sealant in a compression-extension machine shows no damage to the sealant even after 200,000 cycles of ±40 % movement at room temperature. This performance is much better than that of sealants based on other materials, such as STPE, polyurethane, polysulfide, and silicone. These evaluations suggest a high potential of STPA based sealant as durable elastomeric joint sealant, which can be used on a glass, including photocatalytic self-cleaning glass, which functions by decomposing organic materials and by providing a superhydrophilic surface.

Substrate Durability Guidelines Used in Silicone Structural Attachment

Abstract This paper sets forth a procedure for evaluating substrates for durability for use in conjunction with structural silicone glazing (SSG). Lap shear and peel adhesion specimens are evaluated after exposures to various conditions using a modified ASTM C794-06, “Standard Test Method for Adhesion-In-Peel of Elastomeric Joint Sealants,” and ASTM C961-06, “Standard Test Method for Lap Shear Strength of Sealants.” Conditions of exposure include water, sodium hypochlorite (bleach), acetic acid (vinegar), salt fog, UV florescent accelerated weathering device (UVFl), ultraviolet light (UV) exposure, and heat. Evaluation of substrates and the interfaces are completed after tensile testing and visual surface analysis. The silicone structural glazing adhesive used in this evaluation is a high modulus high strength material intended to place the maximum load at the interface. Substrates evaluated include steel, anodized aluminum, galvanized steel, extruded rigid polyvinyl chloride (PVC), glass reinforced thermoplastic resin (fiberglass), and polyvinylidene fluoride (PVDF) painted aluminum. These evaluated substrates are tested to this procedure to show differences in performance and suggest a minimum time frame required for testing. The results and guidelines set forth in this paper provide the foundation for a practice and or a substrate specification for use in conjunction with structural silicone attachment methods.

Development and Laboratory Analysis of Silicone Foam Sealant for Bridge Expansion Joints

Sealing of bridge expansion joint systems is important to protect the structural components below the joint. An elastomeric foam-type joint sealant has been developed for sealing small-movement bridge expansion joints. Laboratory tests including tension, compression, shear, bonding, stress relaxation, cure rate, tack-free time, and water tightness were performed on this sealant. In addition, loading-unloading behavior in tension and compression and effects of immersion in saturated saltwater solution on its engineering properties were investigated. The silicone foam sealant showed an increase in volume of ∼70% on curing and attained approximately 80% of the 21-day curing strength in the first 7 days. Tack-free time for the foam sealant was below 1.5h and comparable to that for the solid sealant. The mechanical test results indicated lower stiffness, greater extensibility, and better bonding associated with the foam sealant compared to the solid (unfoamed) sealant. The foam sealant exhibited smaller loss in extensibility at failure due to saltwater immersion compared to the solid sealant. While in tension both sealants exhibited similar rates of stress decay, in compression the foam sealant was found to relax faster than the solid. Neither sealants exhibited any water leakage during a 96-h test period.

Papers in This Issue

The July 2007 issue of the Journal of Bridge Engineering begins with a paper on vibration of stay cables. In “Vibration Control of Stay Cables of Shandong Binzhou Yellow River Highway Bridge Using Magnetorheological Fluid Dampers,” Li, Liu, Li, Guan, and Ou describe the use of an innovative control algorithm for active and semiactive control of mass-distributed dynamic systems. The longest cables of the Shandong Binzhou Yellow River Highway Bridge were stabilized to suppress vibration using 40 magnetorheological fluid dampers. Field tests were carried out and determined that the semiactive magnetorheological dampers can provide greater supplemental damping than “passive-on” or “passive-off” dampers. Next are three papers on bridge desks. In the first one by Oh, Lew, and Choi, the issue of safety of deck slabs and the resulting frequent repair and strengthening is investigated. In “Realistic Assessment for Safety and Service Life of Reinforced Concrete Decks in Girder Bridges,” the development of a realistic assessment system that can estimate the safety and remaining service life of concrete bridge decks is presented. By determining a realistic and accurate assessment of the bridge deck, the cost of repairs can be eliminated and the loss of use to the public during possibly unnecessary repairs can be prevented. The proposed method uses an assessment of corrosion along with analysis of flexture, shear, and fatigue. The second bridge deck paper is titled “Low-Cycle Fatigue Testing of High-Performance Concrete Bonded Overlay-Bridge Deck Slab Systems” and is authored by Issa, Alhassan, and Shabila. This paper describes a field performance evaluation of a full-scale prototype bridge deck using plain and fibrous latex– modified concrete and microsilica concrete overlays. The study found that this overlay provided good results. “Stiffness and Strength of Metal Bridge Deck Forms,” by Egilmez, Helwig, Jetann, and Lowery, is the final paper on bridge decks. This paper presents the results of the first phase of research investigating the bracing behavior of metal bridge deck forms. While the bracing effects of these forms are used in building construction, due to connection details, the bracing effects are normally not considered when these forms are used in bridge construction. Shear diaphragm tests were conducted to determine the shear stiffness and strength of the forms. The experimental results on the diaphragms indicate the potential for the bracing of steel bridge girders using metal deck forms. The fifth paper in this issue of the Journal of Bridge Engineering is about bridge expansion joints. Malla, Shaw, Shrestha, and Brijmohan in “Development and Laboratory Analysis of Silicone Foam Sealant for Bridge Expansion Joints,” present the results of the development of an elastomeric foam-type joint sealant for use in small-movement bridge expansion joints. The paper presents the results of an investigation using both foam and solid sealants. “Deck-Mounted Steel Post Barrier System,” by Reid, Faller, and Hascall, presents the results of an evaluation of an existing mountable safety barrier system on a fiber-reinforced plastic

Versatile and affordable elastomeric expansion joints launched

Garlock Sealing Technologies has introduced the 104GS General Service Elastomeric Expansion Joints. These joints are intended for new construction projects, water and wastewater treatment plants, power generation facilities, and other industrial applications.

Silyl-Terminated Polyurethanes for Construction Sealants

Abstract Construction sealants produced through the curing of silyl-terminated oligomers (STO) display properties similar to conventional polyurethanes, but they possess several distinct advantages. This paper provides a state-of-the-art review of silane-functional polymers for sealants in construction. Properties of silyl-terminated polyurethanes (STPU) are compared with traditional polyurethanes as well as silyl-terminated polyether (STPE) sealants. Urethane prepolymers, prepared from the reaction of a diisocyanate and a conventional polyol, are end-capped with an organo-functional silane. As a consequence, there are no free isocyanate molecules in the sealant. These sealants show improved adhesion to glass, UV stability, and weatherability. Sealants based on STPU chemistry are presently in use for industrial and transportation applications, which require medium to high modulus. Current work explores methods to reduce the modulus and increase elongation while retaining good cohesive properties. STPU sealants have been prepared with varying isocyanates, polyols, and silanes. They have been evaluated in accordance with several ASTM tests, including those in the ASTM Standard Specification for Elastomeric Joint Sealants (C920). The glass-transition temperatures and rheological characterizations of STO-based sealants are presented. Correlations are made between these fundamental material properties and the sealant's behavior in use, as measured by ASTM test methods. These measurements could provide a method for identifying candidate formulations that are expected to pass more extensive ASTM testing. These material characterizations as well as the results of mechanical property testing are compared for selected STPU, STPE, polyurethane, and silicone sealants.

Elastomeric joint performance of PVC, VC, and FRC Pipes

For rubber ring joints to resist plant root penetration in drier countries, it has been reported and promulgated into some national standards that a sufficiently high contact pressure between the rubber and the pipe must be maintained. The evaluation of the appropriate interfacial pressure to be used has been under discussion for some time and different values have been stated in different standards. This matter has been the subject of considerable controversy, and decisions on the interface pressure used will affect the performance and ease of insertion of a rubber ring joint. This paper reports and discusses previous and current research on root penetration past elastomeric joints, the existing test requirements of elastomeric pipe joints for resisting root penetration given in standards, and the inconsistencies in performance requirements across the different pipe material types. The initial interface sealing pressures for commonly used PVC. VC and FRC joints were assessed and these are discussed in light of the accelerated root intrusion tests performed in Black Hill Flora Centre in Adelaide, South Australia.

Precipitation of fluorouracil in elastomeric infusers with a polyisoprene reservoir and in polypropylene syringes with an elastomeric joint

Precipitation of fluorouracil in elastomeric infusers with a polyisoprene reservoir and in polypropylene syringes with an elastomeric joint

Extension and Compression of Elastomeric Butt Joint Seals

The conventional practice for the design of elastomeric butt joint seals in pavement and building expansion joints is based primarily on standard tests of model seals. The practice does not incorporate structural analysis and does not utilize mechanical properties of the sealant. This study concerns the applicability of a particular load versus deflection equation for the extension and compression design of these seals, i.e., the elementary large compression equation suggested by Payne in 1956 and Gent and Lindley in 1959 for bonded rubber blocks. The study demonstrates, using experiments to measure strain energy density functions for two sealants, by application of these functions in finite-element analyses and by comparison of the finite-element and elementary analysis results, the capabilities and limitations of the load versus deflection equation. In the process, the study introduces an efficient experimental technique for evaluating coefficients of the Rivlin strain energy density polynomial for general application to the analysis of elastomeric structures, and demonstrates the utility of the finite-element-based approach for extension and compression analysis of butt joint seals.

The host response to silicone elastomer implants for small joint arthroplasty

Small joint arthroplasty using medical-grade silicone elastomers has been used for more than 25 years for treatment of rheumatoid, degenerative, or posttraumatic arthritis of the small joints of the hand, wrist, and foot. 1-7 This reconstructive procedure, designed to restore function, relieve pain, and provide joint stability, was facilitated by the special properties of silicone elastomers, ease of fabrication and sterilization, softness, durability, and flexibility. Use of silicone elastomers, however, has recently come under increased scrutiny. Silicone's biocompatibility and the host response to silicone and other biomaterials are currently being reevaluated; the result is an understanding that none of the existing implant materials can be considered biologically inert. In fact, all implants can be expected to elicit some degree of host response. This review will focus on the long-term use and host responses to silicone elastomeric joint implants, including silicone-induced particulate synovitis and lymphadenopathy.

Improvement of the adhesion of silicone to aluminum using plasma polymerization

The adhesion-in-peel test was used to determine peel strength and adhesion characteristics of a cured-in-place silicone elastomeric joint sealant on aluminum substrates. The sealant used was a Dow Corning Type 3145 RTV Adhesive Sealant. The results showed that the silicone sealant had poor adhesive bonding to the untreated aluminum. Plasma polymerization of hexamethyldisiloxane (HMDS) onto the aluminum was seen to move the locus of adhesive failure to being between the plasma film and the silicone. Plasma polymerization of HMDS with oxygen carrier gas produced excellent adhesion and cohesive failure in the silicone was observed.

Embedded piezoelectric sensors to measure peel stresses in adhesive joints

Although peel stresses are believed to be responsible for failure in many adhesive joint geometries, the measurement of these peel stresses has been elusive. In this work, embedded poly(vinylidene fluoride) piezoelectric sensors were used to measure peel stresses in adhesively bonded joints. Piezoelectric KYNAR® film was etched to produce multi-area stress sensors which were bonded into adhesive joints. Calibration results and results for single-lap and elastomeric butt joints are presented. The elastomeric butt joint was compared to an analytical solution for the bond-normal stresses, and the single-lap joint results were compared to finite-element analysis. Promising features and liminations of this technique are discussed.