Strength of glass-filled modified polyphenylene oxide vibration-welded butt joints

The strengths of glass-filled modified polyphenylene oxide (GF-MPPO) welds relative to the strengths of GF-MPPO are shown to depend on specimen thickness. (Modified polyphenylene oxide is a blend of poly (2,6-dimethyl-1,4-phenylene ether) and high-impact polystyrene.) Relative strengths on the order of 70 and 87 percent can be achieved in 6.1 and 3.18-mm-thick specimens, respectively. Welds of GF-MPPO to modified polyphenylene oxide (MPPO) can easily attain the strength of MPPO, the weaker of the two materials. In contrast to MPPO, in which weld strength decreases with increased weld pressure, the strengths of GF-MPPO to GF-MPPO welds and GF-MPPO to MPPO welds, are not affected by weld pressure.     

Strength of polybenzimidazole and phenolic laminate-to-metal joints

Stress concentration effects and strengths of bonded and bolted butt joints were investigated for a glass fabric polybenzimidazole lalminate at room temperatuer and 700°F for a gloass fabric phenolic laminate at room temperature and 500°F. Specimen configurations included: (1) standard tensile specimen, (2) stress concentration specimen, (3) bolted double shear butt joint, (4) bolted single shear butt joint, (5) bonded double shear butt joint and (6) bonded single shear butt joint. Both polybenzimidazole and phenolic laminates exhibited high room temperature tensile strengths and little degradation of that strength occured as a result of elevated temperature exposure. However, low joint effencies (22 to 32%) were obtained for bolted butt joint specimens. Although bonded joints exhibited higher efficiencies, they suffered from a thermal expansion mismatch between the plastic laminate and the Inconel butt plates.     

Vibration welding of thermoplastics. Part IV: Strengths of poly(butylene terephthalate), polyetherimide,and modified polyphenylene oxide butt welds

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration.; The effects of these parameters on weld quality were systematically studied by first butt welding thermoplastic specimens under controlled conditions, over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests. The three thermoplastics investigated are poly (butylene terephthalate), polyetherimide, and modified polyphenylene oxide. Changes in the weld pressure are shown to have opposite effects on the strengths of polyetherimide and modified polyphenylene oxide welds; Also, the weld frequency is shown to have a significant effect on the weldability of polyetherimide. The weldability data for these three thermoplastics are compared with data for polycarbonate. Under the right conditions, the strengths of butt welds in these materials are shown to equal the strength of the virgin polymer.     

Morphology and strength of polycarbonate to poly(butylene terephthalate) vibration-welded butt joints

Under the right conditions, the strength of vibration-welded butt joints of amorphous polycarbonate (PC) to semicrystalline poly(butylene terephthalate) (PBT) are shown to be as high as the strength of PBT, the weaker of the two materials. Optical, scanning and transmission electron microscopy are used to examine the morphology of the weld zone. Acoustic microscopy is used to visualize poorly bonded regions. The effects of the weld parameters on weld strength and weld morphology are considered in detail.     

The hot-tool and vibration welding of acrylonitrile-butadiene-styrene

Thermoplastic window frames are made by hot-tool welding mitered, extruded profiles. The effects of weld process conditions on the strengths of hot-tool butt joints are investigated for a grade of acrylonitrile-butadiene-styrene that was specially developed for window-frame applications. Vibration-weld strength data, obtained on a research machine in which all the process variables can be independently controlled, are used to benchmark strengths of hot-tool welds made on a commercial welding machine. Process differences between hot-tool butt welding and the hot-tool welding of mitered, extruded profiles are discussed.     

Benchmark tests on adhesive strengths in butt, single and double lap joints and double-cantilever beams

The RC99 committee of the Japan Society for Mechanical Engineers conducted the benchmark tests on strengths of adhesive joints using different testing methods. The effects of joint configuration, loading mode, adherend yield strength and so on, on the strength and data scatter were investigated using two typical epoxy adhesives. The strengths obtained by various tests were compared with each other. The relationships among strengths of butt, single lap and double lap joints and fracture toughness were given. Thirteen member institutes of the committee participated in this project. The benchmark results allow us to recognize that the joint strengths are strongly affected by the curing process. The key to obtaining the appropriate joint strength, is precise temperature control inside the adhesive layer for curing. Toughened adhesives do not always give higher joint strengths than untoughened adhesives. The yield strength of adherends much affects the observed lap joint strength of adhesives.     

The Stress-Strain Behaviour of Axially-Loaded Butt Joints

The effects of the stress distribution in the adhesive layer of axially loaded butt joints have been examined theoretically and experimentally. It has been shown that the measured stress-strain behaviour of a butt joint is dependent on the triaxial stress state induced in the adhesive by the restraint of the adherends. This causes a butt joint to yield at a stress which is greater than the uniaxial yield stress of the adhesive. Conversely, the presence of stress concentrations can cause a butt joint to fail at a lower tensile stress than the failure stress of a bulk specimen tested in uniaxial tension. Therefore, the relationship between the strength of a butt joint and that of a bulk specimen of the same adhesive depends on the ductility of the adhesive. Furthermore, if the adhesive obeys a pressure-dependent yield criterion, the compressive yield stress of a butt joint can be much greater than the tensile yield stress of a similar joint and, under some circumstances, compressive yielding of a butt joint may be suppressed completely.     

Strength of Adhesively-Bonded Butt Joints of Tubes Subjected to Combined High-Rate Loads

The dynamic strength of adhesively-bonded joints was investigated experimentally. The strength of the bonded joints under combined high rate loading was measured using the clamped Hopkinson bar method. Tubular butt joints bonded by epoxy resin were used for the experiment. Combined stress waves of tension and torsion were applied to the specimens. The strength of the adhesively-bonded joint was determined by measuring the stress waves propagated in the load output tube of the specimen. It was found that the dynamic strength of the adhesive joints was greater than the static strength under tensile and shear load.     

Cross-thickness vibration welding of polycarbonate,polyetherimide, poly(butylene terephthalate), and modified polyphenylene oxide

In vibration welding of thermoplastics, frictional heat generated by vibrating two parts under pressure, along their common interface, is used to effect welds. In the normal, well-understood mode, the vibratory motion is along the weld seam, which is at right angles to the thickness direction for straight boundaries. But in many applications, such as in the welding of closed seams of box-like parts, this vibratory motion occurs in the part-thickness direction, so that a portion of the molten layer along the seam is exposed to the ambient air during each vibratory cycle. The resulting reduction in temperature can affect weld quality. The process phenomenology and the weld strengths of such cross-thickness vibration-welded butt joints are investigated for four neat resins. Weld amplitudes and weld pressures are shown to affect the strengths of 120-Hz welds differently. It is shown that strengths on the order of the strengths of the neat resins can be achieved in 250-Hz butt welds.     

Comparative study of weld-line strength for unfilled and glass-filled thermoplastic polyamide-6 materials

The injection molding process is widely accepted for the processing of engineering thermoplastics due to the ease of manufacturing complex designs. Weld-line is a defect occurring in injection molded parts when two flow fronts join each other. At weld-line locations, parts exhibit lower mechanical strength mainly due to inadequate intermolecular diffusion and fiber orientation anisotropy. The present work is aimed at investigating and comparing weld-line strength for unfilled and glass-filled polyamide-6 materials. To achieve this, polyamide-6 unfilled, 30% glass-filled, and 50% glass-filled materials are used to manufacture plaques. The special-purpose mold is designed to obtain plaques with and without weld-lines with help of Moldflow simulations. The specimens for tensile tests are then cut from molded plaques and experimental testing is conducted to evaluate tensile properties. Fractured surfaces of specimens are examined using a scanning electron microscope. The results demonstrated a significant drop in tensile strength and modulus for glass-filled material weld-line specimens when compared to specimens of no weld-line. However, for unfilled specimens, tensile strength and modulus are almost the same for samples with and without weld-line. A reduction in tensile strength of 13%, 49%, and 57% is observed for unfilled, 30% glass-filled, and 50% glass-filled polyamide-6 material respectively.     

Stress distribution and mechanical strength of T- and L-type adhesive-bonded joints subjected to applied bending moments

The stress distribution in the adhesive layer of T- and L-type adhesive-bonded butt joints between rigid adherends has been measured experimentally, and the equations relating the maximum stress in the adhesive layer to the bending moment applied to these joints and to the joint dimensions derived. The equations are used to calculate the adhesive strength of T- and L-type joints from the measured breaking load. These strengths show reasonable agreement with experimental values.     

Fatigue strength of vibration welded thermoplastic butt joints

Fatigue data are presented for the strengths of 120-Hz vibration-welded butt joints of four resins: the three amorphous polymers polycarbonate (PC), polyetherimide (PEI), and modified polyphenylene oxide; and the semicrystalline polymer poly(butylene terephthalate). Data are also presented for the fatigue strength of 250-Hz vibration welds of the high-temperature polymer PEI. For all the welds, fatigue strength was evaluated through 10-Hz, tension-tension, load-controlled tests at an R value (ratio of minimum stress) of 0.1. Surprisingly, for all the stress levels studied, none of the PC test specimens failed at the welds, indicating that the fatigue strength of PC welds equals that of the base resin. This is not true of the other three resins, except at relatively low stress levels. For each of the four resins, macrographs are used to highlight the differences between the failure surfaces of monolithic specimens and specimens that failed at the welds.     

Experiments on the induction welding of thermoplastics

In induction welding of thermoplastics, induction heating of a gasket, made of a ferromagnetic‐powder‐filled bonding material and placed at the interface of thermoplastic parts to be joined, is used to melt the interface; subsequent solidification of the melt results in a weld. Tensile tests on induction butt‐welds of polycarbonate (PC), poly(butylene terephthalate) (PBT), and polypropylene (PP) are used to characterize achievable weld strengths, and microscopy is used to correlate weld strength with the morphology of failure surfaces. In PC, PBT, and PP relative weld strengths as high as 48%, 43%, and 55% of the respective strengths of PC, PBT, and PP have been demonstrated. Relative weld strengths on the order of 20% have been demonstrated in PC‐to‐PBT welds.     

Strength of epoxy adhesive-bonded stainless-steel joints

The strength of stainless-steel joints bonded with two epoxy adhesives was investigated. The experimental programme included tests on single-lap and butt joints, as well as thick-adherend and napkin ring shear tests. Results suggested that the tensile and shear strengths of the epoxy adhesives were quite similar. However, finite element (FE) analyses raised doubts on the true adhesive strengths, due to the complex stress state in joint tests and pressure-dependent adhesive behaviour. In spite of some uncertainties, FE analyses showed that failure could be fairly well predicted by a maximum shear strain criterion.     

横向载荷对含表面裂纹对焊接头疲劳裂纹扩展速率影响的研究

研究了双向载荷作用下对焊接头表面裂纹的疲劳扩展规律。采用经精确标定应力强度因子幅值的双向十字形试样,在电液伺服双轴向疲劳试验机上对母材分别为16MnR 和 Q235-B 这两种钢的对焊试板进行了疲劳裂纹扩展试验。同时,将其结果分别与单向应力下对焊接头及母材的疲劳扩展速率进行了比较,为制定我国在役压力容器缺陷评定规范提供了参考数据。     

Silicon sputtering as a surface treatment to titanium alloy for bonding with PEKEKK

Thermoplastics, having strong polar or hydrogen bonding groups, are potential candidates for thin film bonding. In this investigation, a thermoplastic polymer poly(ether ketone ether ketone ketone) (PEKEKK) is used as an adhesive to bond the titanium alloy (Ti-6Al-4V). The titanium alloy is silicon-sputtered to improve the bond strength to PEKEKK. The bond strengths of butt-joined specimens prepared using silicon-sputtered, silane-coated, sodium hydroxide-anodized round bars of titanium alloy as adherends are determined and compared with that of untreated titanium alloy round bars. Of the various thicknesses of silicon layers studied, layers that are 200 Å thick proved to have a more durable bond, as demonstrated by soak test results in Ringer's solution. It is observed that silicon sputtering enhances the bond strength of titanium alloy/PEKEKK butt joints and provides a more resistant interface to intruding water. The combination of anodization followed by silicon sputtering further improves the durability of the bond. It is confirmed by XPS analysis that fracture does not take place between the silicon and the titanium substrate. Wetting studies by contact angle method using water as test liquid, indicate significantly better wetting after silicon sputtering for Ti-6AL-4V adherends.     

A Method of Estimating the Strength of Adhesive Bonded Joints of Metals

The strength of adhesive bonded joints is investigated both analytically and experimentally. The deformed states of lap joints under tensile shear loading are analysed by the finite element method on the assumption of elastic deformation. A method of using the adhesive strength law is proposed to estimate the joint strength. The adhesive strength law is experimentally determined by subjecting butt joints of two thin-walled tubes to combined axial load and torsion. The strength of lap joints is determined by adopting the adhesive strength law to the adhering interface as well as the strength law of adherend and adhesive resin. The calculated strain distribution and strength of the joints are compared with the experimental results. The effects of the joint configurations on the deformation and strength are discussed. It is shown that the proposed method is useful to predict the joint strength.     

A Method of Estimating the Strength of Adhesive Bonded Joints of Metals

The strength of adhesive bonded joints is investigated both analytically and experimentally. The deformed states of lap joints under tensile shear loading are analysed by the finite element method on the assumption of elastic deformation. A method of using the adhesive strength law is proposed to estimate the joint strength. The adhesive strength law is experimentally determined by subjecting butt joints of two thin-walled tubes to combined axial load and torsion. The strength of lap joints is determined by adopting the adhesive strength law to the adhering interface as well as the strength law of adherend and adhesive resin. The calculated strain distribution and strength of the joints are compared with the experimental results. The effects of the joint configurations on the deformation and strength are discussed. It is shown that the proposed method is useful to predict the joint strength.     

Joining strength of sheet molding compounds

Bonding and bolting strengths of a sheet molding compound (SMC-R30) are investigated. Epoxy adhesives are found to give good bonding strength. Surface pretreatment does not affect bond strength. Artificial weathering has practically no effect upon bond strength. Bolting strength depends on the width of the specimen for a certain bolt size. Bolting gives stronger joints than bonding.