Composite Flow Moulding With New Victrex® Polymer Gives Ultra-High Specific Strength

Lancashire, UK — Composite Flow Moulding (CFM) is an innovative process for manufacturing endless fibre reinforced components with superior strength. The fully automated technology was developed by Icotec AG, headquartered in Altstätten, Switzerland. The company's innovative use of endless carbon fibres in a thermoplastic matrix of Victrex® PEEK™ polymer results in ultra-high specific strength of up to 600 MPa/g/cm3, exceeding that of aluminium (˜50 MPa/g/cm3) and titanium (approximately ˜300 MPa/g/cm3). Proven applications such as fasteners are produced in high volumes in one single step, without the need for post-treatment, and of consistent high quality.

Conventional thermoplastic processing techniques do not permit extremely high fibre content. Furthermore, it is not possible to process long or endless fibres without damaging them. Fasteners subjected to high mechanical loads are therefore machined from blanks. This process does not provide an optimum orientation of the fibres in the threaded area. In contrast to this, CFM with Victrex® PEEK™ polymer produces fasteners which can withstand high load transfers without damage to the thread.
The pultrusion moulded Victrex® PEEK™ polymer rods are aligned and fed into a heated closed pre-heating cavity from where they are axially transferred to the mould and formed under pressure. In the manufacture of screws, the technique produces helically reinforced threads, which are well protected against abrasion when the screw taps the bore. In addition, a transitional fibre orientation zone transfers the forces introduced in the threads to the core.This permits high mechanical loads without shearing off the thread. Glass fibre reinforced parts can even be used to tap threads in aluminium or magnesium sheet.

The semi-crystalline Victrex® PEEK™ polymer matrix has a melting point of 343°C, a glass transition temperature of 143°C and a continuous use temperature of 260°C. Victrex® PEEK™ polymer excels in friction and wear resistance, low flammability, extremely low smoke emission and minimum toxicity of the developing gasses as well as outstanding chemical resistance and good electrical properties. Fibre reinforcement can be carbon-, glass-, ceramic- or even metal-based to meet the specific needs of the final application. For instance, fasteners made from carbon fibre filled Victrex® PEEK™ polymer with a density of 1.6 g/cm3 offer flexural strength ranging from 800 to 1,000 MPa and tensile strength of up to 450 MPa. Depending on the fibre orientation, the ratio of the dynamic to static load bearing capacity (?dyn/?stat) can still be within the range of 60% to 90%. The type and volume content of the selected fibres control the overall properties of the moulded components, whilst the process parameters provide the means for reinforcing individual sections.

Fasteners manufactured using the CFM process with Victrex® PEEK™ polymer are used in a wide range of technical applications. In motor sport, Formula 1 teams have chosen CFM screws for their superior strength and reliability in fastening chassis and important aerodynamic components, while at the same time permitting the use of conventional tools. In aviation, CFM fasteners have been evaluated in extensive test programmes for numerous assembly as well as insulation elements.
Furthermore, CFM nuts have been used successfully in marine applications where their initial fastening function is complemented by outstanding loosening resistance.

Current developments include CFM fasteners for innovative applications in aerospace, where the key focus is on weight reduction, thermal expansion and stiffness matching with other composite materials. Ongoing advances by Icotec will extend the use of CFM with Victrex® PEEK™ polymer beyond secondary components into the area of primary structural parts.

SOURCE: Victrex®