Applied Adhesion Science最新文献

The purpose of this study was investigate the influence of different surface treatments on the shear bond strength of two different type of artificial resin teeth repaired with composite resin. Fifteen (15) artificial teeth of each material (CR-composite resin and AR-acrylic resin) were divided into four parts and then embedded in acrylic resin. After, the teeth were separated into eight groups according to the surface treatments prior to the repair: control group (c), adhesive application (a), sandblasting (S) and sandblasting followed by adhesive application (Sa). Next, a composite resin cylinder (??=?0.95?mm e h?=?2?mm) simulating a repair was built onto each surface. The specimens were submitted to a microshear bond test after 24?h, using a universal testing machine (1?mm/min, 50 kgf) until fracture. The data was subjected to two-way analysis of variance (ANOVA) and Tukey test, with a significance level of 5%. ANOVA showed statistical difference for the interaction artificial teeth material* surface treatment (p?=?0.001). CR teeth (29.79?±?11.54?MPa) showed higher bond strength mean values than AR (18.48?±?9.73?MPa). Regardless the artificial teeth material, Sa (36.92?±?6.16?MPa) treatment showed the higher bond strength values. The highest bond strength value was found in CRSa (45.93?±?7.13?MPa) and the lowest was found in ARc (5.38?±?0.90?MPa). Based on the results, tooth material should be taken in account in order to choose the best surface treatment and achieve suitable bond strength values when a repair is necessary. For artificial teeth in acrylic resin, applying an adhesive system is the best procedure, with or without sandblasting the alumina particles. However, for artificial teeth in composite resin, an association of sandblasting followed by applying an adhesive system showed more promising bond strength values.

The aim of this study is to evaluate the degree of conversion of light-cured resin cement subjected to activation through the interposition of lithium disilicate ceramic produced according to two manufacturing techniques. Cylindrical specimens of RelyX? Veneer resin cement were generated based on each manufacturing technique (CAD/CAM—computer aided design/computer assisted manufacturing, n?=?5 or pressed ceramic technique, n?=?5). Next, the specimens were washed in distilled water, dried with absorbent paper and stored in containers filled with distilled water at 37?°C for 24?h. Specimens from each group were subjected to attenuated total reflectance Fourier transform infrared (ATR-FTIR) in order to evaluate their degree of conversion. Data about the degree of conversion (%) were subjected to analysis of variance and to Student’s t-test (α?=?0.05%). The degree of conversion of RelyX? Veneer was statistically higher in the CAD/CAM manufacturing technique (39.83?±?0.35%) than in the Press one (37.59?±?0.62%). The light-cured resin cement activated through ceramic structure reinforced with lithium disilicate generated through the CAD/CAM manufacturing technique showed higher degree of conversion than the one generated through the Press manufacturing technique.

The optimization of mechanical properties of adhesive bonds is of interest especially in structural applications. Besides transferring stresses, bondlines can also provide additional functionality, such as measuring deformations in structural timber applications by electrically conductive adhesives. This study investigates the influence of a thermal postcure treatment of polyurethane bonded wood joints. Bonded beech wooden samples were manufactured with three adhesives—a commercial one-component polyurethane for structural laminated timber and two modified ones, filled with electrically conductive particles. Adhesive bonds were subjected to a subsequent postcuring at 80 and 95?°C for 1 and 48?h, respectively. Mechanical properties of the bonds were studied on the macroscopic level by tensile shear tests and the properties of the cured adhesive on the microscopic level by nanoindentation. As a result, the tensile shear strength slightly dropped with addition of filler, while all specimens still fulfilled the requirement of EN 302-1 in dry condition. Nanoindentation revealed minor decreases in mechanical properties of the cured adhesive with postcuring time for two adhesives and a different reaction of carbon black filled polyurethane, as the creep factor decreases with the thermal postcure.

Durability and safety of adhesively bonded joints are of major importance in structural applications. The probability of failure of a bonded assembly after a certain period of time may be influenced by various aging effects including e.g. temperature and humidity. The correlation of results obtained from accelerated laboratory aging tests to long-term aging under service conditions often remains an unsolved challenge. In the present work, computer-based tools for non-linear regression analysis, estimation of reliability and lifetime prediction have been applied to experimental results obtained by accelerated aging of adhesively bonded shear specimens. Results obtained with an epoxy based adhesive and a hot-dipped galvanized steel as adherend are discussed. The modeling of the aging behavior is performed with combined functions referring to the EYRING as well as the PECK model which both appear appropriate for describing the experimental data. The safety prediction, based on the probability of failure as well as the safety factor β, is performed by using the EYRING model which fits the experimental data in a more conservative manner.

Over the last two decades, the repair of existing engineering structures using fiber reinforced polymer composites has attracted a great attention by aerospace industry, as it is more economical than replacing new. With an increased use of composite material in aerospace field, it is thus essential to restore the structural integrity by repair of damaged part. Concerns regarding the long term durability of composite repair bonded joints have been a major obstacle for critical component of aerospace structures. This paper reviews the current research on the environmental durability of adhesive bonded repair of composite structures to focus on the durability concerns and suggestion on the research needed in this area. The most important environmental factors (moisture and temperature) are reviewed thoroughly and also combined environmental effect. Finite element methods used to predict the environmental influence on the composite bonded joints are briefly reviewed. Finally, the paper concludes with key findings, opportunities and future research topics in order to develop cost effective, better quality and reliable composite repair bonded joints.

Adhesively bonded joints are being widely used in the fabrication process of aircraft and automobile structures. Surface roughness is an important parameter of product quality that strongly affects the performance of mechanical parts, as wel as production costs. This parameter highly influences the mechanical properties overall of such structures. The effects of UV radiation on the single lap joints manufactured with different types of surface preparation and temperature were examined before and after UV exposure. Sandblasting, sanding and chemical cleaning were used as surface preparation and two test temperatures were used for investigation, 25 and 115?°C. The results of those tests showed that surface preparation highly influences shear strength, but does not affect the stiffness of the tested joints. Temperature also influences the shear strength and stiffness. UV radiation contributes to increase shear strength and do not degrade the tested single lap joints.

Water-based ink formulations containing wax, surfactant, and defoamer additives were prepared and printed on polyethylene film substrates. Standard test methods for adhesion, rub resistance, and gloss were done on the printed polyethylene films. Quantitative methods for the assessment and evaluation of the three print properties were developed. Image analyses were done to quantify adhesion and rub resistance. Quantitative measurement was done to quantify gloss. Data were analyzed using mixture design modelling and optimization. Modelling results show that adhesion and gloss are described by special cubic model equations, while rub resistance is described by a linear model equation. Contour plots and 3D surface graphs were generated showing the response surfaces of the print properties. The effects of varying the mass fractions of wax, surfactant, and defoamer on adhesion, rub resistance, and gloss were determined. It was found that increasing wax increases rub resistance, while increasing surfactant increases gloss, and increasing defoamer increases adhesion. There is dependency found between the mass fraction of wax, surfactant and defoamer with respect to the rub resistance, adhesion and gloss. Multi-objective optimization revealed that optimum adhesion, rub resistance, and gloss is obtained by a formulation containing equal mass fractions of wax and surfactant but no defoamer.

The joining process of seam bond is used in automobile construction because of the non-visible joints on mounted parts such as doors, hoods or luggage compartment doors. With these components, a structure-providing inner panel is joined with the outer panel, which is visible to the customer. Besides providing stability, particularly in the event of a crash, the joining level is also filled with adhesive to increase the stability and to prevent the ingress of moisture that causes corrosion. These mechanical connections must be tested to ensure that the requirements for proper bonding have been met. As the destructive test used today requires metallographic laboratory with special trained personnel, significant scrap cost and a time consuming process control loop, considerable efforts are being made to develop a capable non-destructive and as far as possible in-line test method. State of the art non-destructive inspection systems for seam bonds are insufficient regarding full part accessibility and reliability in terms of detectability and validation. This paper is focussed on new developed free configurable three-transducer ultrasonic phased array technology including algorithms for data validation and evaluation for an automated process control loop in the automotive car body shop. The paper end with an statistical classification based on an 5-month measurement campaign under industrial in-line conditions. In a first step, a list of possible defects was collected and the detectability in different seam areas was calculated by sound field simulation of the amplitude signals. Second, based on the results from simulation, a measurement setup as excitation sequence was defined. Based on the theoretical findings a inspection system was designed and realized. Within a measurement campaign the inspection system was evaluated in terms of detectability of minimal defect size under non-laboratory conditions. This includes a permanent proof of coupling conditions, monitoring of misalignments, e.g. tilting and surface defects of the car body. In the last step, the testing system is build up and tested within the assembly line. These measurement results show that the identification of common process defects is possible.

In the context of lightweight structure design for the transportation and robotics industries, new types of composite structures are being developed, in the form of trusses made of fiber-reinforced polymer composite members of small diameter (a few millimeters thick at most). Some concepts of wound trusses can be found in the literature, but in more general cases, for which a predefined wound truss shape is not usable, individual truss members must be joined together. The axial strength of the composite members allow them to carry a high load, and the joints between those members should be strong enough to carry this load as well. With the objective of developing an efficient joint design for an application in thin composite trusses (member thickness ranging from 0.5 to 5?mm), finite element models of several adhesive joint designs were built, and their strengths were compared. The comparison was made using the same joint configuration (number of members, member cross-sectional area, joint dimensions) and loading conditions. Adhesive failure was considered in this study, and the strength of each design was determined from the value of the peak maximum principal strain in the adhesive layer, as this failure criterion is suitable for the toughened adhesive material used in the models. A trade-off between the strength, weight and manufacturability of each joint design was made in order to conclude on their overall performance. Results suggested that, among the joint designs modelled, round-based composite rods inserted in a tubular metallic piece are the most efficient in terms of strength-to-weight ratio.

The most economic and environmental problems result from burial agricultural waste materials. The main objective of the present investigation is to assess the usefulness of agricultural waste in mortar admixture. These materials are expected to reduce the density of the admixture, and thus producing lightweight mortar.This study aims to study the effect of using pistachio shells as partial replacement of sand on the properties of cement mortar. Furthermore, the effect of density, absorption, and compressive strength of cement mortar were also obtained.Ordinary Portland cement from Kufa Cement Plant was used with a water cement ratio of 0.48 and a mix proportion of 1:3, also six percentages of pistachio shells were used (10, 20, 30, 40, 50 and 60% by weight of fine aggregate).A total number of 84 mortar cubes were casted with 12 cubes for each mixture ratio. From 84 mortar cubes 21 cubes were utilized to calculate the average water absorption and 63 cubes were utilized to calculate the average density and compressive strength.Compressive strength values of the mortar cubes were evaluated at 7, 14, 28?days at different percentage replacement levels obtaining a range of values of 6.78, 8.92 and 14.1?MPa, respectively at 20% replacement.The density values were reduced with the increment in replacement levels until it reached (1.21 and 1) gm/cm³ at 28?days with replacement percentages of (50 and 60%) respectively.Water absorption was increased with the increment in replacement levels and reaching (6.04%) at (60%) replacement level.