JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009 - 54

KNOW-HOW Ductile prepregs …/… Formable aligned-fibre composite materials (typically 5-10%); • axial deformation stresses, compared with the continuous filament precursor, are dramatically reduced under normal forming conditions (typically between 1 and 2 orders of magnitude); • strains up to 50% can be sustained during forming without necking and subsequent failure. Focus About Integrated Materials Technology IMT is developing complementary technologies for the automated manufacture of composite laminates and for enhancing the formability of the resulting products. The combined technologies aim to produce formable, highperformance composite materials at affordable prices. The company has a particular interest in thermoplastic composite technology. used to produce customised forming blanks for parts manufacture. Initial applications foreseen to benefit from the process include small complex parts such as cleats and brackets for aircraft structures; complex beams and spars; skins with doublers, door and window surrounds; and large parts currently needing automated fibre placement. Conclusions Fig. 3: A four hole pattern repeat. Benefits of Perform micro-perforation In contrast to the approach of the earlier work using chopped or stretch-broken fibres, which severed and aligned the fibres before impregnation, prepreg micro-perforation severs the fibres after alignment and impregnation. This has the important advantage that the existing standards of fibre alignment, fibre volume fraction and the condition of the fibre-matrix interface are maintained, whilst no new chemistry or binders are introduced. A particularly attractive feature of the process is that it can be applied to the material either globally or only to regions where enhanced formability is required. Apart from reducing the cost/kg of the process, this also allows the performance advantage of continuous reinforcement to be maintained in the extensive areas of a structure where improved formability is not required. Both thermoplastic and thermoset materials can be processed and, by using currently qualified materials, the certification process can be simplified. The need for new, more compliant materials that can be processed rapidly and cheaply is now recognised as an essential step in the industrialisation of composite manufacturing. Attempts to impregnate assemblies of aligned discontinuous fibres have so far failed to deliver materials which can offer an acceptable balance of mechanical and deformation properties. The use of laser micro-perforation to process existing UD prepregs is enabling the production of discontinuous aligned fibre materials with the required balance of mechanical and deformation properties. Moreover, rather than starting from scratch to create new materials, this approach has been shown to have important technical and commercial advantages. Much work remains to be done on the preferred methods for forming Perform materials and on the modelling of their forming behaviour. Contacts: roger_a_ford@hotmail.com bobgriffiths@btinternet.com References [1] Edwards H. E., Evans D. P.; ICCM-3 Paris 1980, pp. 1620-1635 [2] Richter H.; ICCM-3 Paris 1980, pp. 387-398 [3] Bontemps G., Giroux X.; JEC Composites Magazine, 2007, 33, pp. 64-66 Applications of the Perform process The process was designed in two potential formats: • a high-speed automated process, which can be integrated with the material supplier’s prepreg production equipment to supply continuous material on reel; • a stand-alone machine for the composite manufacturer, to be [4] Okine R. K., Edison D. H., Little N. K.; J. Reinforced Thermoplastic Composites, 1990, 8, pp. 70-90 [5] Pipes R. B.; in Flow & Rheology in Polymer Composite Manufacturing, Ed. Advani S. J., Elsevier, Amsterdam 1994 [6] Ford R. A.; Materials & Design, 2001, 22, pp. 177-183 [7] IMT Ltd; Patents GB 0768942, DE 69523596-6, FR 0768942, & US 6027786 54 jec composites magazine / No50 July-August 2009

JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009