Improvement of Weld Line Strength in Injection Molded FRTP Articles

Hamada, Hiroyuki; Maekawa, Zenichiro; Horino, Tsuneo; Lee, K.; Tomari, Kiyotaka

doi:10.3139/217.880131

Cited by 22 publications

(6 citation statements)

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“…mould 11 , the pressure differential created by two independent injection units 12 or different systems generating an oscillating movement of the melt [13][14][15] .…”

Section: Discussionmentioning

confidence: 99%

Weldlines in Injection-Moulded Reinforced Thermoplastics: Mechanical Performance Improvement through Intrusion Induced Fibre Reorientation

Debondue

Fournier

Lacrampe

et al. 2004

Polymers and Polymer Composites

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The effect of processing conditions on the mechanical properties of a weldline in short glass fibre reinforced polypropylene was investigated. It appears that the presence of a weldline has a deleterious effect on the tensile properties, with a serious loss of strength and rigidity. The optimisation of the process parameters through a Taguchi methodology showed some improvement, the properties remaining however quite distant from those of specimens without weldline. The analysis of the fibre arrangement around the weldline gave clues to explain this situation. In the vicinity of the weldline, the typical skin-core structure was deeply disrupted with a skin layer almost non-existent. Therefore, most of the fibres were oriented perpendicularly to the direction of loading, resulting in poor load transfer. Calculations showed that the strength was almost reduced to the transverse resistance of a unidirectional composite because of the very specific orientation of the fibres around the weldline. The generation of a back-flow in the melt, thanks to a differential gate solidification, brought some reorientation of the fibres and some increase in the properties.

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“…mould 11 , the pressure differential created by two independent injection units 12 or different systems generating an oscillating movement of the melt [13][14][15] .…”

Section: Discussionmentioning

confidence: 99%

Weldlines in Injection-Moulded Reinforced Thermoplastics: Mechanical Performance Improvement through Intrusion Induced Fibre Reorientation

Debondue

Fournier

Lacrampe

et al. 2004

Polymers and Polymer Composites

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“…Injection pressure and injection speed have also been investigated and only slight improvement has been observed when they are increased. Hamada et al 24 have observed a large increase in weld line strength when the holding or packing pressure is increased (which is the level of pressure maintained to insure complete mold filling). Other r e~e a r c h e r s ,~~-~~ have not observed improvement with weld line strength as a function of packing pressure.…”

Section: Wool9 and Wool And O'connor''mentioning

confidence: 97%

“…Wendt further suggests maintaining flow after formation of the weld line to encourage penetration of the two flow fronts. Hamada et al 24 describe a "backflow" technique where a pressure imbalance is used to shift the interface by having one flow project into the center of the opposing flow. The resulting weld line has a larger interfacial area and increased interfacial strength.…”

Section: Wool9 and Wool And O'connor''mentioning

confidence: 99%

Knit lines in reaction injection moldings

1990

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Knit lines in reaction injection molding (RIM) are formed when a fluid flow front passes through the mold cavity and must pass around objects in its path. Factors were ordered in importance of their effects on the deterioration in mechanical strength associated with knit lines. In order of decreasing importance, reactcmt temperature, mold temperature, and relah've location Cfrom the product) of the knit line sample were found to affect the knit line strength.

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“…This technique has been shown to give an increase of about 20% in the weld line strength of a 20 wt % glass fiber reinforced polycarbonate. 6 The push-pull process (PPP) technique is more complicated, but uses the same idea of forcing melt through the weld line after it has formed. The necessary pressure difference is achieved with two injection units, which first inject simultaneously to fill the part.…”

Section: Introductionmentioning

confidence: 99%

“…The additional cavity is filled right after the main cavity containing the weld line; by creating a pressure difference, this forces the still‐molten material to flow across the weld line and so reorients the fibers. This technique has been shown to give an increase of about 20% in the weld line strength of a 20 wt % glass fiber reinforced polycarbonate …”

Section: Introductionmentioning

confidence: 99%

Weld line improvement of short fiber reinforced thermoplastics with a movable flow obstacle

Janko

Spiegl

Kaufmann

et al. 2015

J of Applied Polymer Sci

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Short fiber reinforced (SFR) thermoplastics are ideal materials from which to manufacture complex technical parts in high volumes with low energy expenditure. The orientation of the fibers, and hence their reinforcing effect, depends strongly on the nature of the cavity and on the injection molding process. One disadvantage of SFR thermoplastics is a significant decrease in mechanical properties in the areas of the weld lines, due to suboptimal fiber orientation as the melt streams reunite at these points. Common mold-based and process-based optimization techniques alter the fiber orientation after the formation of the weld line. The mold-based approach presented here, on the other hand, operates at the time the weld line is formed: by redirecting the melt streams, it moves the weld line and improves the fiber orientation. A prototype mold is described, and samples produced from it with both standard and modified weld lines are compared with flawless specimens. The new technique yields a large rise in flexural strength and a smaller but significant improvement in tensile properties.

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Improvement of Weld Line Strength in Injection Molded FRTP Articles

Cited by 22 publications

References 0 publications

Weldlines in Injection-Moulded Reinforced Thermoplastics: Mechanical Performance Improvement through Intrusion Induced Fibre Reorientation

Weldlines in Injection-Moulded Reinforced Thermoplastics: Mechanical Performance Improvement through Intrusion Induced Fibre Reorientation

Knit lines in reaction injection moldings

Weld line improvement of short fiber reinforced thermoplastics with a movable flow obstacle

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