THERMOPLASTIC COMPOSITES | MATERIALS
Allegheny Performance Plastics, based in
Leetsdale, PA, US, which is a processor of high- performance specialty polymers, offers a technol- ogy concept in which two different material technologies are combined into a hybrid compo- nent. In this case a thermoplastic composite is injection overmoulded to produce a hybrid composite part. The Thermoplastic Composite Injection Overmoulding (TPC IOM) concept, which the company presented in 2021 at The Composites and Advanced Materials Expo in the US, combines the high strength and stiffness benefits of thermo- plastic composites with the design flexibility and cost effectiveness of injection moulding. According to Gregory Shoup, President of Allegheny Perfor- mance Plastics, this results in a best-in-class total cost of ownership.
Shoup says the company’s TPC IOM technology
offers numerous benefits in structural applications compared to the use of traditional metals, such as titanium, steel, aluminium, or specialty alloys. This includes a weight reduction by a factor of 1.5 to 2.5; the ability to increase part functionality by incorpo- rating multiple functions which lowers assembly; the opportunity to operate in series production at moderate to high-volume production; and the benefit from the inherent properties of the selected polymers, which can include heat-, impact-, corro- sion-, and wear-resistance, dielectric properties, thermal insulation, low coefficient of friction, recyclability and lower environmental impact. “Recently, numerous requirements have
emerged relative to environmental footprint and cost competitiveness which are driving the need for new material technologies and advanced manu- facturing techniques,” says Shoup.
TPC IOM has been developed as a combined stamp forming and injection moulding process which occurs in a single process, or in a two-step approach where the thermoplastic composite is heated separately then transferred into the injection moulding unit where it is overmoulded.
Demonstrator Allegheny Performance Plastics teamed up with Solvay’s Materials Science Application Center at its Alpharetta, GA, site to select the thermoplastic composite material and overmoulding material. Allegheny Performance Plastics and Solvay worked on the integration of the TPC IOM concept into a part design. The companies investigated the design, simulation, manufacturing, and analysis of a test TPC IOM demonstrator part to show the key benefits of the technology. The hybrid demonstra- tor part earned a fourth place showing in the
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enabler technology category of the 21st Automotive Awards hosted last year by SPE Central Europe. The initial phase of the study is based on the production of a generic, omega shape demonstrator part that is overmoulded with a complex rib structure to form the hybrid TPC IOM component. The overmoulded material to the thermoplastic com- posite part intentionally contains a few real-life challenges, such as varying cross-sectional rib thicknesses, with injection from the thin towards the thick rib section, and areas of lower density in the moulding, as well as relatively long flow lengths with areas of backfilling of the ribs, and tight radius compound bends. The thermoplastic composite part is
made from a Solvay thermoplastic composite tape, with a matrix of polyether- ketone-ketone with aligned, continuous UD fibre reinforcement (APC PEKK-FC). The pre- preg tape is 0.14 mm thick and is 145 gsm, 34% RC, says Allegheny Performance Plastics. The overmoulding material selected is a Solvay Ketaspire KT-880 CF30 PEEK material with 30% short carbon fibre. The TPC insert is stacked into a laminate and consolidated into 500 mm x 300 mm panels (1.68 mm thick) using a contained steel compression tool and oil-heated press in a thermal compression moulding cycle, operating at 377° C, 20 bar for 20 minutes. A CNC machine cuts 75mm x 25 mm x 15 mm thermoplastic composite inserts from the laminated sheet. Prior to stamping and overmoulding the
laminates are dried for 12 hours at 125° C in a low-dewpoint desiccant oven to minimise decon- solidation of the TPC due to water migration during preheating. The TPC insert was designed to be suspended into a pair of infrared heaters using a flat spring clamp on one of the narrow edges, then loaded into the injection mould tooling. Two holes in the TPC insert are for retention of the part within the injection mould. Allegheny Performance Plastics used an IR
heater system consisting of two 255 mm x 255 mm infrared panels outfitted with an on/off sensor, PID temperature controller and optical pyrometer on each side to enable closed loop surface tempera- ture control. IR heater set temperature, dwell time and cool-down were also investigated. The IR heating variables were optimised to achieve a laminate draping temperature of 375° C when being formed in the tool cavity. A thermocouple embedded into the test TPC stack allowed for
January/February 2023 | INJECTION WORLD 19
Above: Allegheny Performance Plastics’ hybrid demonstrator featured in the Automotive Awards hosted last year by SPE Central Europe
IMAGE: ALLEGHENY PP
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