ISSN:0032-3888    

DOI:10.1002/pen.760320902

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractDeep penetration welding of polymers can be carried out at high speed with relatively low laser power. This results from an efficient coupling CO2laser radiation to polymers that leads to volume heating. A brief review of energy coupling and heat transfer effects in polymers under CO2laser welding conditions is given. Some examples of low power (10 to 100 watt) CO2welding of polypropylene and polyethylene at depths of up to 1.5 cm are discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760320903

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThin microtomed samples from hot‐tool butt welds of polypropylene pipes are subjected to uniaxial tensile stress using a specially built instrumented microtesting machine. The deformation of the interface between the weld and the bulk polymer is measured by an optical method. An analysis of these measurements is carried out using the finite element method, and contours of the effective stress are obtained. There is a steep stress gradient at the junction of the weld flash and the bulk polymer, although the stress concentration factor is relatively low. The stress is essentially constant in the bulk polymer apart from the region near the weld zone. Tests on samples without the weld flash show that the maximum stress occurs within the weld zone. This is consistent with long‐term tests on larger samples, where the fracture is found to initiate within the weld. The method of analysis enables the stress‐strain response of the weld material to be deter

ISSN:0032-3888    

DOI:10.1002/pen.760320904

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractFatigue 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 anRvalue (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

ISSN:0032-3888    

DOI:10.1002/pen.760320905

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractUltrasonic welding of oriented polypropylene (OPP) using tie‐layer materials has been examined. The thermal cycle at the joint interface was evaluated using a high speed data acquisition system, and concurrent changes in horn displacement (penetration) and the output power were monitored. The model explaining process operation involves four phases, i.e., I–where heating occurs because of the stresses generated in asperities on the contacting surfaces; II–where the whole tie‐layer reaches the melting point; III–where the polymer melt is subjected to intense heating from viscous dissipation and is squeezed out; and IV–where the joint cools after welding. In the early stages of ultrasonic welding the heat generated at asperities on the contacting surfaces leads to melting of the tie‐layer/oriented polypropylene interface within 50 ms. The tie‐layer heats up because of a combination of viscoelastic dissipation and heat conduction from the oriented polypropylene/tie‐layer interface, and the rate of temperature rise at the midline of the tie‐layer is in the range 200°/s to 400°/s. The reduction in thickness of the test specimens (penetration) is negligible up to the time when the tie‐layer melts completely, and then changes rapidly when the melted polymer at the joint interface is squeezed out. The influence of machine parameters (amplitude and contact pressure) and of tie‐layer Melt Flow Index is also examined. The total time required for completion of the welding process decreases when the amplitude and applied pressure are increased. The use of low Melt Flow Index tie‐layers produces peak temperature as high as 600° at the bondline, and little material is ejected during the

ISSN:0032-3888    

DOI:10.1002/pen.760320906

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe influence of tie‐layer Melt Flow Index on the lap‐shear strength of ultrasonic welds in oriented polypropylene (OPP) has been evaluated. The tie‐layer Melt Flow Index was varied from 0.03 dg/min to 2600 dg/min; the highest lap‐shear strength properties were obtained using tie‐layers that had melt flow index values between 30 and 100 dg/min. When using low Melt Flow Index tie‐layers, hot spot formation and concomitant changes in fusion zone and heat‐affected‐zone dimensions produced stress concentrations that promoted failure in oriented polypropylene material away from the bondline region. When very high Melt Flow Index (2600 dg/min) tie‐layers were used, the mode of failure during lap‐shear testing was a mix of cohesive, in oriented polypropylene, and adhesive failure. The molecular weight of material at the bondline was not markedly affected by the thermal cycle produced during ultrasonic welding. Only the flash ejected when using low Melt Flow Index tie‐layers exhibited any evidence of degradation; it is suggested that the ejected flash may have been degraded because of a combination of thermal, cavitation, and therm

ISSN:0032-3888    

DOI:10.1002/pen.760320907

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractA study to investigate fusion bonding (welding) of AS4 graphite/polyetheretherketone (PEEK) thermoplastic composites is presented. Processing studies are conducted for resistance welding preconsolidated AS4/PEEK laminates in both unidirectional and quasi‐isotropic configurations using PEEK and polyetherimide (PEI) film at the joint interface. All bonding was done under a constant displacement process. The influence of processing time, initially applied consolidation pressure, and the rate of heat generation on weld performance is examined through lap shear and Mode I interlaminar fracture toughness testing. A rapid increase in strength with processing time that asymptotically approaches the compression molded baseline is measured. Weld times for quasi‐isotropic lap shear coupons are significantly shorter than those with a unidirectional lay‐up. Variation of the initially applied consolidation pressure is shown to have little influence on the lap shear strength of PEEK film welded lap joints. A discussion of the mechanisms allowing void formation during the welding process is given. Bond strength test results are correlated with ultrasonic C‐scans of the weld

ISSN:0032-3888    

DOI:10.1002/pen.760320908

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe objective of this study was to develop mathematical relations for predicting the strength of adhesive‐bonded double‐lap joints under cantilevered bending. Based on the strength of composite materials theory, two models were proposed to predict the stress‐strain distribution and vertical deflection of the laminates and the adhesive under this loading condition. The first model was based on the basic beam theory with the assumption that every cross section in a plane before bending remains plane after the bending load is applied. In the other model, a strain gap between each bonded surface is assumed. Based on the second model and the predicted peel failure mode, the effects of shear modulus of the adhesive, joint length, and adhesive thickness on the joint strength were evaluated. Scotchply composite laminates were used as the adherends of the double‐lap joints in the experimental investigation. An Instron machine fitted with a special apparatus was used for conducting the experiments. By the attachment of strain gages to the adherends and through the use of a dial indicator, the theoretical models were verified experim

ISSN:0032-3888    

DOI:10.1002/pen.760320909

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760320901

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY