CW Blog

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It’s June 11 as I write this. I am on United flight 81 en route to the 2019 Paris Air Show (June 17-23) by way of Manchester, U.K. I have attended the Farnborough Air Show before, but this will be my first time at the Paris event.

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Producing composite parts with a class A finish is not the Holy Grail — there are plenty of companies that do this on a routine basis. However, doing so using resin infusion without expensive tooling or gelcoats and at a rate of one part per hour? Well, that is something unique.

Plastics Unlimited was started 25 years ago by Terry and Nancy Kieffer, explains their son Dakota Kieffer, sales and marketing director for the company. “They were farmers in Iowa and had started looking for a new and growing industry,” he explains, “They thought plastics would be better than welding or woodworking and they did not want to compete with their neighbors. They looked at injection molding, rotational molding and recycling plastics, but then came across thermoforming, and really understood it.” (Thermoforming uses heat and vacuum/ pressure to shape thermoplastic sheets into shaped parts.)

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By: Daniel Adams 7/8/2019

Mechanical testing of textile composites

Although standardized test methods for fiber-reinforced composites are used for a wide variety of fiber forms, most of these test methods were developed with a focus on composites with continuous fibers aligned in unidirectional layers. Typically available as prepreg tape, these unidirectional material forms are commonly used in aerospace and other industries because they provide the highest stiffness and strength. However, many other continuous fiber forms are commonly used, including woven and braided fabric layers. For these textile composites, it’s often necessary to modify the standardized test methods and consider other specialized methods as well. In this column, we consider the aspects of textile composites that require special test considerations as well as the most common modifications made to test methods to accommodate them.

Perhaps the most significant test method modifications for textile composites result from textile composites’ periodic geometry, which is produced by their undulating fiber tows. This repeating pattern of the textile architecture allows for a unit cell to be identified, defined as the smallest geometric element of the textile architecture that represents the periodic textile pattern. Examples of a unit cell for a two-dimensional weave and a triaxial braid are shown in Fig. 1. Under uniform loading, these textile architectures produce strains that can vary in magnitude by a factor of three within a unit cell1. Since these mechanical tests are intended to obtain average or bulk properties of the textile composite, the test section of the specimen must be sized appropriately. As a result, the identification of the material’s unit cell size is an important step in establishing the required dimensions of the test specimen.

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The Composites Index closed May at 53.3, extending its ongoing record of consecutive months of expanding industry activity. The latest Index reading is 7.6% lower compared to the same month one year ago, indicating slowing growth within the industry over the past year. In the year-to-date period the Index has averaged 53.8, indicating consistent but modest business activity expansion. Index readings above 50 indicate expanding business activity, while a value of 50 indicates no change and a reading below 50 indicates contracting business activity. Gardner Intelligence’s review of the underlying data indicates that the Index was propelled by production which was followed by employment, new orders and supplier deliveries. The Index — calculated as an average — was pulled lower by backlogs and exports; both contracted during the month.

May’s supplier delivery data was notable for expanding more slowly than new orders, production and employment. The last time this occurred was late 2017, shortly before a record-setting surge in new orders activity in early 2018 that caused supply chains to scramble in reaction to meet demand. The latest data may suggest that upstream suppliers have largely restocked those formerly depleted inventories.

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