Composites Today

Magazine For Composites Professionals

Glass veils prove successful in Fibre Metal Laminates

A recent study conducted by the university of Edinburgh on vacuum-infused thermoplastic fibre-metal laminates has highlighted the performance benefits of Technical Fibre Products’s (TFP) 6 gsm glass nonwovens as adhesive carriers within Fibre Metal Laminates.  

Figure taken from Maguire J.M. et al (2023) ‘vacuum-infused thermoplastic fibre-metal laminates – advances in bonding and recycling’ materials today communications, 37, pp 1-5.  

Fibre Metal Laminates (FML) combine layers of composites and metal, creating a unique set of material properties that are an effective balance of the advantages and disadvantages of their constituents.  

Initially developed for the aerospace industry, FMLs have many advantages; they are lightweight, have a high damage tolerance, and demonstrate good fatigue, corrosion, and impact properties. The versatility and mechanical properties of FML technology show promise for expansion into other sectors as well, such as wind energy and marine transport, especially when combined with new reactive thermoplastic systems.  

Combining these technologies presents challenges, particularly the optimisation of the metal-composites interface for good adhesion. The constituent materials are dissimilar, potentially causing weak interfacial bonding leading to delamination and loss of integrity.  

The study, titled ‘Vacuum-infused thermoplastic fibre-metal laminates – Advances in bonding and recycling’, evaluates the utilisation of nonwovens as a carrier for the adhesive to improve the bond line uniformity and interfacial bonding, the latter of which is characterised by a high Interlaminar Shear Strength (ILSS). TFP’s lightweight nonwovens are already used extensively in the aerospace industry as a carrier or support for adhesive films in more traditional composite layups. They facilitate uniform wet out of adhesive, setting the bond line to ensure a defined and consistent film thickness, whilst ultimately improving the resilience and handling of the final product. 

This study investigated the strength of the bonding within fibre-metal laminates (FMLs), evaluating the impact of using 3 different glass fibre carrier veils with areal weights of 6, 17, and 34 g/m2. The FMLs were manufactured using a standard vacuum infusion process (VIP), with an adhesive carrier (fabricated using TFP’s glass veil and methacrylate adhesive) incorporated between the layers of composites and aluminium – the stacking sequence of each FML was [0/Al/0], as shown in Figure above. 

The laminates were subjected to Short Beam Shear (SBS) testing to evaluate the ILSS and determine which carrier delivered the most effective bonding. The results indicated that TFP’s 6g/m2 lightweight fine glass veil performed best; the thin, highly porous veil architecture enabled rapid and consistent impregnation with the adhesive to create a thin, uniform bond line.  

The study demonstrates the importance of the use of TFP materials in this area, enabling the use of FMLs in new sectors and applications. Key takeaways from the study include:  

  • Ensuring a consistent and uniform bond line is important for the successful transition of FML technology to an industrial scale. The integration of TFP’s lightweight fine glass as an adhesive carrier enables the necessary control over bond line thickness and maintains uniformity. 
  • A thin glass fibre veil can be utilised as an adhesive carrier to improve bond line uniformity without reducing the interlaminar shear strength which would indicate a disruption in interfacial bonding. Measurement of the Interlaminar Shear Strength (ILSS), a critical composite property, indicates superior results with TFP’s 6gsm fine glass veil. 

To view the full study visit:  

Glass fibre reinforced thermoplastic material used in lightweight automotive shift fork

Envalior (Germany), a leading global engineering materials solution provider, announced that it has partnered with KOKI TECHNIK Transmission Systems GmbH (Germany), a leading Transmission Shifting Systems manufacturer, to deliver a shift fork used within an E-Powertrains Decoupling Unit. KOKI chose ForTii® ACE PPA for its shift fork application because the material offers extreme high stiffness up to 160°C, design freedom and maximum wear resistance without the need for additional bushings.

KOKI’s main objective for its shift fork application was to make it lightweight with high stiffness and maximum wear resistance. KOKI also wanted to reduce cost of the application when compared to a heavily machined aluminium part.

ForTii® ACE is a competitive material—with its overall technical characteristics—when it comes to the substitution of aluminium components within decoupling units used in E-Powertrains as well as regular transmissions, according to Ron Krotwaar, Advanced Development Expert, Lightweight Solutions for Envalior.

“Nearly all functionalities—assembly interfaces, gearing and detection systems—can be integrated in a well-designed component made from a thermoplastic glass fibre reinforced compound without additional processes. As a result, potential cost savings can be achieved,” said Martin Wollenberg, Head of Business Development at KOKI. “With its superior performance at competitive material costs, ForTii® ACE allows a successful substitution of aluminium components with well-designed composite solutions.”

With KOKI’s advanced CAE simulations, plus Envalior’s (Computor Aided Engineering) CAE services and predictive technologies, the two companies worked as a team to further improve the accuracy of KOKI’s advanced simulations. Envalior provided technical support and services to optimize the geometry for mechanical performance and processing when designing the shift fork. The KOKI / Envalior team worked together on anisotropic material behavior and material models. Plus, they shared knowledge and experiences about simulating and interpreting results. In addition, Envalior supported KOKI with viscosity measurements.

“The team captured the material’s behaviour and understood how to process the results specifically for Envalior’s ForTii® ACE MX53 material,” said Krotwaar. “The KOKI and Envalior team enabled a more robust part performance and design to the safe limits. With Envalior’s deep material knowlegde and experience with material behaviour, Envalior enabled KOKI to readjust product design, simulation and tooling where needed, to get the best out of the material’s performance.”