Study of Processing Conditions on the Forming of Ribbed Features Using Randomly Oriented Strands Thermoplastic Composites

Abstract

Compression molding of randomly oriented strands (ROS) composites offers the possibility to manufacture complex parts with a fast processing cycle. In this paper, effects of pressure, strand size, temperature, and material placement in the mold cavity on the quality of a T-shape part were studied experimentally with carbon/polyether ether ketone ROS composites. Minimum filling pressure was obtained for the consolidation of a 25-mm deep cavity. Parts processed at filling pressure showed a void content no greater than 1.2%. Increasing pressure to 70 bar resulted in decreased void content as low as 0.03%. Mechanical testing of the T-shape showed similar strengths for parts processed at filling pressure and higher (70 bar). At the component level, initial strand placement greatly affected mechanical performance as the presence of a knit line was responsible for a reduction of 60% in tensile strength. The main findings show that processing a complex feature at filling pressure P fill was sufficient to reach nominal mechanical properties. This suggested that moderate porosity was not detrimental to the mechanical performance for the given tests where fatigue performance was not evaluated.

Mechanical characterisation and modelling of randomly oriented strand architecture and their hybrids – A general review

“…Leblanc et al. 80 studied the effect of pressure, strand size, temperature and material placement in a 25.4 mm deep rib cavity and reported that low pressures were sufficient to fully consolidate parts with smaller strand (3.17 mm × 6.35 mm) of carbon/PEEK at 400°C. Parts processed at filling pressure (10 bars) had a void content <1.2% while high pressure (70 bars) decreased the void content to 0.44% and 0.03%.…”

A recyclable epoxy for composite wind turbine blades

“…Recent reports have described the state of the art for reuse and recycling of composite materials [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Recycling of thermoset composites (particularly epoxies) presents a challenge due to their highly cross-linked structures and insolubility under mild conditions [18,19].…”

Compression molding of reused in-process waste – effects of material and process factors

“…Likewise, Selezneva et al 15,16 determined mechanical properties of such composites as a function of both material and test specimen characteristics, identifying trends similar to those observed for thermoset composites, and proposed a stochastic approach for modeling mechanical performance. 17 Leblanc et al 18 studied the effect of processing conditions on the forming of ribbed features, showing that complex features can be produced if the molding pressure exceeds a sufficient filling pressure, and that initial strand placement can reduce mechanical performance if it creates merging flow fronts. Levy et al 19 proposed and demonstrated a model capable of predicting the inter-strand void content for discontinuous CF/ PEEK parts, and produced design charts relating process parameters, chip properties, and final part characteristics.…”