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Managing Editor  | June 2017

Manufacturer explores selective reinforcement of discontinuous composites

PlastiComp, Inc., a Minnesota-based manufacturer of long-fiber reinforced thermoplastics (LFT) composites), recently published a case study on AZO Materials about the selective, structural reinforcement of discontinuous, fiber-reinforced composites to improve load to fatigue life.



PlastiComp, Inc. wrote about incporporating LFT compounds to reinforce composites.
(Wikimedia Commons)


According to the case study, adding unidirectional, continuous fiber inserts in the tensile regions of structural parts through insert-molded LFT compounds increased load to fatigue life of one million cycles to 50-70 percent of the material strength.


The case study explained, “Since the pultrusion process employed in the production of LFT granules or pellets can be easily modified to manufacture unidirectional tapes, it was decided to produce this new form and employ them as continuous-fiber inserts in high-stress regions of LFT injection-molded parts.


It continued, “The process involves consolidation of resin-impregnated fiber strands in a rolling mill, thus eliminating the granulating or pelletizing stage. These unidirectional tapes were analyzed for fiber content and physical uniformity. The thickness of the tapes was typically 0.25 mm and the width (12-50 mm) was chosen to match the compressive and tensile surfaces, initially in 12 mm wide ASTM test-bars and then in injection-molded parts. In initial experiments, standard ASTM tensile test-bars were injection molded with tape-inserts on their flat surfaces.”


Using the tapes improved tensile strength from 288 to 320 MPa and flexural strength from 366 to 458 MPa. The tensile modulus increased from 25.8 to 26.8 GPa and flexural modulus from 20.4 to 27 GPa.


The case study noted, “In initial experiments, the tensile and flexural strengths are increased by 11% and 25%, respectively. A pronounced increase is observed for flexural properties due to the presence of the tape-insert on the tensile-surface of the I-beam and when the flexural load is taken up by the continuous fiber reinforcement.”


It concluded, “Due to the additive properties of tape inserts, tapes of varying matrix polymer and fiber content are currently being tested for load-transfer from the polymeric matrix to unidirectional fibers, mechanical properties, and failure mechanism. Initial study shows that unidirectional tapes have only 20% of the tensile strength of the reinforcing fibers. This tensile strength loss should be linked with load-transfer mechanisms in tape-testing and the standardization of tensile testing of samples of 0.25 mm thickness.”


Read the full case study at http://www.azom.com/article.aspx?ArticleID=14036

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