Philip J. Bates

Laser Light Transmission Through Thermoplastics as a Function of Thickness and Laser Incidence Angle: Experimental and Modeling

It is important to accurately measure and predict the laser light transmission through unreinforced and reinforced thermoplastics if candidate materials are to be assessed for laser transmission welding (LTW) applications. This paper presents the results of laser transmission measurements through unreinforced polyamide 6 (PA6) and 10% glass fiber reinforced polycarbonate of various thicknesses and corresponding to various laser incidence angles (angle between the incident laser beam and the normal to the transparent part). A novel transmission measurement method, developed by the authors, was employed. A model, utilizing the Fresnel specular surface reflection conditions as well as accounting for refraction, absorption and reflection of the laser light through the bulk material, was used to predict transmission as a function of thickness and laser incidence angle. Results of transmission tests on both materials showed that, for a given thickness, the transmission decreases as the laser angle of incidence increases. In addition, at any given laser incidence angle, the transmission decreases as the thickness increases. The advantage of the model is that it requires only one experimentally determined constant for a given material. Good agreement existed between the experimentally measured transmission and the model prediction for the range of thicknesses and laser incidence angles studied.

Effect of Polyamide 66 on the Mechanical and Thermal Properties of Post-Industrial Waste Polyamide 6

Post-industrial waste (PIW) polyamide 6 is successfully used in lieu of commercial virgin polyamide 6, in several automotive applications. The presence of polyamide 66 in the final formulation may affect the mechanical and thermal properties of the PIW polyamide 6 materials. Using unreinforced polyamide 6 from PIW and commercial sources, it was found that the addition of polyamide 66 (below 10 wt.%) lowered the crystallization rate and crystallinity level of all polyamide 6 materials. The thermal and mechanical properties of glass fiber (GF) reinforced PIW polyamide 6 compounds with and without polyamide 66 were also studied. Differential scanning calorimetry (DSC) showed that reinforced materials without polyamide 66 had a higher level of crystallinity. Furthermore, dynamic mechanical analysis (DMA) showed that reinforced compounds without polyamide 66 also had a faster storage modulus buildup immediately after injection molding. Reinforced PIW polyamide 6 compounds without polyamide 66 also exhibited higher tensile and higher vibration weld strengths as well as a thicker heat affected zone (HAZ) than those with polyamide 66, leading to the conclusion that polyamide 66 had a detrimental effect on crystallinity level and consequently on the mechanical properties of GF-reinforced PIW polyamide 6 materials.

Tensile and Fatigue Evaluation of a Glass Reinforced Recycled Nylon Blend: Effect of Polypropylene Contamination

ABSTRACT Tensile strength was measured on 30 wt% glass fiber-reinforced postconsumer waste and postindustrial waste recycled nylon blends. Fatigue tests were performed under load control at a stress ratio of 0.1 at temperatures of 24 and 120°C. It was found that increasing temperature led to a significant decrease in both tensile strength and fatigue life. For unwelded postindustrial waste/postconsumer waste blends, the endurance ratio was approximately 50% regardless of the temperature. For welded postindustrial waste/postconsumer, a similar endurance ratio was observed at room temperature, but it decreased to 33% at 120°C due to the presence of polypropylene found in the postconsumer component. GRAPHICAL ABSTRACT

Matching of laser intensity distribution for laser transmission welding of thermoplastics

Laser transmission welding of polymers is becoming more and more important in industrial applications. In contrast to other polymer welding processes, for example hot plate welding or vibration welding, the exact definition of the major process tool, the laser beam, is challenging. The comparison of investigation results with each other can be very difficult, because of, for example, the different intensity distribution and the specimen geometries. In this study, a method to match the laser power profiles of two different laser systems was developed. Shear-test results confirm that statistically equal weld strengths can be achieved when laser power profiles and test geometries are matched.

WELD READ-THROUGH DEFECTS IN LASER TRANSMISSION WELDING

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