Main topics of this issue:

Composites Overmolding 2018, Novi, Michigan

Overmolding of thermoplastic composites is a technology in which a thermoplastic composite is thermoformed and subsequently injection overmolded. The near-net-shape manufacturing process is well suited for automated large series production of complex 3D structures with excellent structural performance and a high level of function integration. The first dedicated overmolding conference was held at June 13-14 in Novi, Michigan. TPRC Business Developer Mark Bouwman presented an overview of TPRC’s overmolding activities at this two-day conference.

TPRC initiated the COMPeTE overmolding project in early 2015. In this multilateral cooperation, the TPRC consortium and external partners from the industry bundled their strength to tackle two major challenges: 1. The interface strength between the composite laminate and injection molded polymer and 2. The residual stresses and resulting shape distortions of overmolded parts. Models, simulation tools and processing guidelines have been developed in order to understand and simulate both phenomena. TPRC successfully demonstrated a two-step and automated one-step overmolding process in the COMPeTE project: a Carbon-PEEK demonstrator part has been developed based on a thrust reverser blocker door (aero-engine part). The follow-up project COMPeTE II started in 2017 and focusses on performing a structural analysis to predict part performance. A new characterization tool and technology demonstrator are being developed within this project.

Interested to learn more about overmolding? Do not hesitate to contact us for more information about overmolding and check out all our various upcoming events and presentations on the TPRC website!

Upcoming events to get in touch with TPRC:

• SAMPE Conference Southampton (11th - 13th September 2018)
• ITHEC Bremen (30th – 31st October 2018)

Research spotlight: squeeze-flow

As thermoplastic composites are used more and more in the industry, the generated amount of production scrap increases significantly. The TPC-Cycle project targets this yet un-used production scrap by developing a recycling route for high-end and high-volume markets, with the objective to retain the high mechanical properties of the thermoplastic composites. The process starts by shredding scrap material to flakes with a size of several centimeters. The fibers in these flakes maintain a length of around 20 to 30 mm to retain high mechanical properties. These flakes are then fed into a low-velocity extruder that melts the polymer and blends the flakes. Finally, the thoroughly mixed and heated molding compound is extruded and directly transferred to a press for compression molding. The mold temperature remains constant during this compression molding process, which limits the amount of time for the material to flow and to fill the mold cavity.

The flowability of the molding compound in the mold cavity is determined by the process and material parameters, such as the fiber length, degree of mixing and fiber volume fraction. Understanding the effect of the process and material parameters on the flow behavior is crucial when designing and manufacturing parts from this recycled material. A new experimental ‘squeeze flow’ setup has been developed by the TPRC to characterize the flow behavior of the molding compound experimentally. The developed knowledge will be transformed into predictive models and processing guidelines, which is indispensable for a successful implementation of this technology by the industry.

You will find more information about recycling of thermoplastic composites on our website!

Discover the insights of thermoplastic composites with TPRC

TPRC provides training on thermoplastic composites for members and non-members. All trainings are a combination of 50% theoretical lectures and 50% practical work in our lab facilities. The course Introduction to Thermoplastic Composites explains the typical features of thermoplastic composites and the participants are introduced to processing technologies during hands-on work in our lab. This practical work comprises consolidation techniques, press forming, laser-assisted tape placement, welding, mechanical testing and non-destructive testing (NDT).

The Advanced Forming course is an advanced-level course and provides state-of-the-art knowledge on press-forming thermoplastic composites. This course covers the theoretical background of the process and explains the material characterization techniques for forming. The practical work comprises simulating the forming process using the AniForm software and performing press forming trials on our 200 tons press.

The next Advanced Forming course will take place 6-7 November 2018, followed by the course Introduction to Thermoplastic Composites on 4-5 December 2018. Get inspired and contact us for more information!

Publication: continuum mechanics analysis

Akkerman, R. (2018). A continuum mechanics analysis of shear characterisation methods. Composites Part A: Applied Science and Manufacturing, 109. 

We, as TPRC, believe that a thorough theoretical understanding of materials and processes is required to deliver on the promise of thermoplastic composites as the material of choice for light-weight components. We are proud to say that scientific director Remko Akkerman contributed to this with a journal publication on continuum mechanics analysis of shear characterization methods.

The paper presents that process simulations have shown to be very useful for optimizing the forming process and for shortening the development time of new (thermoplastic) composite products. These simulation models require accurate material data. TPRC has spent considerable efforts in developing characterization procedures to acquire the material data reliably, reproducibly and in a limited amount of time.

The publication provides a novel approach to analyze and interpret the data from one of such characterization tests: the Uniaxial Bias Extension test. This novel approach makes it possible to easily distinguish fiber stresses from the essential behavior in shear, for which the test was developed, and is, unlike existing rate independent theories, suited for thermoplastic composites in particular.

Interested in more research insights at TPRC? Reinforce your business and get in touch with us!

Follow the TPRC social channels

Make sure to follow TPRC on LinkedIn, on Twitter and on YouTube to be kept up to date with the latest innovations and developments of our thermoplastic composites research. Join, and innovate with us!