Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - IMCoLoR (Injection Moulding with Continuous Local Reinforcements)

Teaser

IMCOLOR’s main objective is the development of a novel process for the advantageous combination of injection molding and thermoplastic automated fiber placement with in-situ consolidation (TP-AFPisc) to manufacture a continuous fiber reinforced air cycle machine part wherein...

Summary

IMCOLOR’s main objective is the development of a novel process for the advantageous combination of injection molding and thermoplastic automated fiber placement with in-situ consolidation (TP-AFPisc) to manufacture a continuous fiber reinforced air cycle machine part wherein high-performance thermoplastics like PEEK are involved. The TP-AFPisc process is a change compared to the state of art, where composite structures typically build within process chains. TP-AFPisc is integrating the major steps of material deposition and consolidation without expensive autoclaves and represents an additive manufacturing process.
PEEK injection molding is a challenge in combination with undercuts and thermoplastic composite inserts. Typically, these inserts are only half-sided overmolded, to keep the insert in position during injection. However, there is no complete encapsulation of the sensitive composite inserts, that can protect the exposed fibers or ensure an overall part surface with the accuracy of injection molding standards. Therefore IMCOLOR uses load path tailored composite inserts manufactured by TP-AFPisc for complete encapsulation by PEEK injection molding.

Objectives:

Technical
•Local continuous reinforcement of injection molded parts. Sufficient consolidation of the local reinforcement inserts. Firmly bonding between inserts and injected material.
•Direct manufacturing of 3D tape-layed complex insert structures with core technology.
•Manufacturing of removable, pressure- and bending-resistant cores for TP-AFPisc 3D inserts.
•Injection molding tools with exact fixations for inserts.
•Overmolding of inserts by fixation in an injection moulding tool.
•CF-PEEK injection molding with lost core technology to enable undercuts.
•Raise of pressure resistance of the ACM part at elevated temperatures.
•Surface properties like non-reinforced injected parts. No surface treatments.

Scientific
•Implementation of lost core material for CF-PEEK injection molding
•Overmolding and complete encapsulation of TP-AFPisc inserts in PEEK compound

Ecological
•Weight and cost reduction
•Reduction of fuel consumption, CO2 and NOx emission
•Avoid hazardous Cr6+ surface treatment by replacing metal by CF-PEEK

Work performed

Project activities so far: design work related to process demonstrator parts, process development and demonstration, development of test cases

The activities are conducted in cooperation between the project partners with in-depth experience to lead the multidisciplinary project to success: Development of TP-AFPisc tools, lost core technology, tape placement, automated sensor data analysis and mechanical test scenarios are in focus of TUM. The scientific partner TPRC develops the injection strategies, gives advice on material selection and simulates tooling concepts. TPRC carries out the injections on a KraussMaffei machine. The industrial partner apppex has strong experience in fast production of prototype tools and takes care of tool design, molds and integration of inserts. The tier 1 supplier FACC concentrates on NDT part inspection.

In the beginning a model part (simple geometry) and the requirements were defined. High temperature, pressure and containment requirements have to be fulfilled. A tough material system was chosen: TenCate LM-PAEK TC1225 for TP-AFPisc and Victrex PEEK 150CA30 for injection molding. The material combination is well suited for overmolding, because the prepreg material has a lower melting point than the injection compound. Hence, a good bonding exists between injection compound and insert material. TUM and TPRC investigated the material for optimal machine setup. 3D inserts were produced and overmolded to model parts. The overmolding strategy, tooling concept, insert fixture and material selection was proven. Machine data logs and micrographs show a good material quality. The parts show occasionally out-of-plane fiber wrinkling of thin-walled inserts. Delamination between plies are observed in the wrinkle. The preheating temperature and high pressure loads during PEEK injection can cause fiber buckling. However, it is not considered a critical defect by the Topic Manager. In order to keep a flawless insert fiber architecture, it is recommended to perform fitting trials with preheated mold and insert parts. Then the tooling can be adapted to the optimal tolerance to prevent fiber buckling. The dimensional control will be carried out on coordinate machines, micrographs and by CT scans.
In order to set up destructive tests, TUM managed overspeed tests with an impactor of the Topic Manager in cooperation with the subcontractor SPINTEST Müller GmbH.
TUM elaborated a solution to realize undercuts in overmolded demonstrator parts. The high process loads and polymer shrinkage ask for a high resistant lost core material. IMCOLOR aims for the novel use of salt cores in PEEK injection molding. The big advantages are its water solubility and recycling capabilities.

Finally, the consortium would like to especially thank Toray Advanced Composites (TenCate), Victrex and DELO Industrial Adhesives for their interest in the project and kind support with material.

Final results

The aim is to develop a synergy between injection molding and the TP-AFPisc process beyond the state of the art, which enables future lightweight design at high mechanical performance with automated, reproducable production techniques under ecological friendly conditions. Injection molding is a wide spread technology for thermoplastic processing, but restricted to the use of short fiber material. It offers a large spectrum of geometric freedom and enables high production rates. In high-loaded structures, continuous fiber reinforcements are demanded because of their excellent thermomechanical properties. However, due to the casting process, it is not possible to use continuous fibers in injection molding. IMCOLOR closes this gap and enables a high efficient utilization of material. The expensive endless fiber are only used in the necessary sections of the part. The fiber architecture is precisely adapted to the user’s needs by engaging TP-AFPisc manufactured inserts. Effort in trimming of composite parts is minimized and scrap is reduced. No surface preparation is necessary for the inserts, because they are bonded to the polymer by autohealing during overinjection. The final part profits from the high loadable endless fiber reinforcement that is completely covered by injection molding compound. The injection molding process adds its benefits in terms of surface quality, tolerances and protection against environmental influences (e.g. impactors, corrosive media) to the sensitive endless fiber architecture.

IMCOLOR’s advanced technology in process and material will be shown by demonstrators. The consortium will prove the new developments in process, component and scanning trials to show their suitability for the aerospace application. The novel process is not solely limited to aerospace applications. The high degree of automation and flexibility of machines make it possible to use the technology in automotive industry, too. Although IMCOLOR investigated a difficult to process material system like PEEK, its conclusions can be applied to other engineering plastics.

Therefore the project is an important step towards an emission-reduced mobility by applying advanced lightweight material and contributes to maintain a healthy environment in the future.