Resin Infusion under Flexible Tooling RIFT John Summerscales

Resin Infusion under Flexible Tooling (RIFT) John Summerscales Advanced Composites Manufacturing Centre School of Marine Science and Engineering University of Plymouth, PL 4 8 AA, United Kingdom

Outline of presentation • other manufacturing processes • four variants on resin infusion – advantages and disadvantages – applications using the process • notional cost comparisons • brief summary

Manufacturing processes • • spray hand lamination hot press vacuum bagging and autoclave cure Resin Infusion under Flexible Tooling (RIFT) Resin Transfer Moulding (RTM) filament winding pultrusion

Manufacturing processes • Vacuum bagging and autoclave cure – wet resin or prepreg lamination followed by bagging and cure under pressure • Resin infusion (RIFT) – A range of intermediate techniques • Resin transfer moulding (RTM) – long-range flow of resin into a dry fibre pack preloaded into a defined mould cavity.

Change from hand lay-up ? • Increased consolidation pressure – 1 atmosphere = full vacuum = 105 N/m 2 (10 tonnes/m 2) • Occupational Exposure Levels – – Germany/Sweden 20 ppm France/Spain 50 ppm United Kingdom 100 ppm EU harmonisation (long overdue) in 201 x ? • Pollution Prevention and Control Act 1999 – styrene has an odour threshold of 0. 034 ppm i. e 630 µg/m 3

Why resin infusion ? • Resin transfer moulding (RTM) – as mouldings increase in size, mould clamping forces become excessive • Vacuum bagging and autoclave cure – premium price for pre-impregnation of the raw materials – long cycle times – capital cost of equipment

Resin infusion • Muskat patent application, 1945 – the fibrous base to be impregnated … preferably in a substantially dry state – drive the resin into the base to impregnate it – one tube being connected to a source of resin and the other to a vacuum pump – complementary moulds appear to be free to move together under vacuum • process introduced to UK by Scott Bader in 1946

“Acronym” anarchy ! • • • • • CIRTM: co-injection RTM Crystic VI: vacuum infusion (Scott Bader) DRDF: double RIFT diaphragm forming (University of Warwick) LRI: liquid resin infusion MVI modified vacuum infusion (Airbus) Quickstep use of liquids for enhanced heat transfer in infusion RFI: resin film infusion RIFT: resin infusion under flexible tooling (ACMC Plymouth) RIRM: resin injection recirculation moulding SCRIMP Seeman Composites Resin Infusion Molding Process (TPI) VAIM: vacuum-assisted injection moulding VAP vacuum assisted processing (patented by EADS) VARI: vacuum assisted resin injection system (Lotus Cars) VARIM: vacuum assisted resin injection moulding V(A)RTM: vacuum (-assisted) resin transfer moulding VIM: vacuum infusion moulding. VIMP: vacuum infusion moulding process VM/RTM Light: a hybrid RIFT/RTM (Plastech) VIP: vacuum infusion process

Resin infusion • RTM with one tool face replaced by a flexible film or a light splash tool • flow of resin results only from vacuum and gravity effects • mould cavity varies with local pressure • thickness of the part depends on pressure history

Resin Infusion under Flexible Tooling (RIFT 1 of 4) • Basic RIFT process: – resin flows in the plane of the fabric between the mould and the bag KEY Resin feed Vacuum Reinforcement – slow process due to limited pressure gradient – may need flow enhancement tows within the reinforcement

RIFT 1: slow flow in the process Special fabrics • Commercial process needs flow-enhancing tows, e. g. – Brochier Injectex – Carbon fabrics from Carr Reinforcements – Glass fabrics experimental programme with Interglas-Technologies

Potential advantages Process • use most resin systems. • use most forms of reinforcement fabrics. • large structural components can be fabricated. • relatively low tooling costs for high-performance components. • better than wet-laid components with little modification of tooling. • heavy fabrics more easily wetted than by hand lamination. • lower material costs than for prepreg and vacuum bagging.

Potential advantages Performance • higher fibre volume fraction gives improved mechanical performance. • minimal void content relative to hand lamination. • more uniform microstructure than hand lay-up. • cored structures can be produced in a single flow process. hand-lamination resin infusion

Disadvantages Process • complex process requires different skills to hand-lamination. • emphasis on preparation, not on the actual moulding process. • sensitive to leaks (air paths) in the mould tool and the bag. • quality control of the resin mixing is "in-house". • slow resin flow through densely packed fibre • uneven flow could result in unimpregnated areas/scrap parts. • not easily implemented for honeycomb core laminates.

Disadvantages Performance • only one moulded surface • low resin viscosity means lower thermal and mechanical properties. • thinner components have lower structural moduli • laminate thickness dependent on flow history (next slide) • licensing costs where aspects of the process patented in the USA

Fabric compressibility in RIFT • A B C 2. 2 mm 2. 0 mm 1. 8 mm 0 2000 4000 Time (s) 7500 11500 • • • nine layers of plain weave E-glass/UPE resin compression by vacuum lubrication by resin front at A relaxation as pressure gradient falls resin inlet closed at C

Comparison of HL and RI resins SP resin systems Property hand lamination infusion Ampreg 20 Prime 20 Units Viscosity m. Pa. s Tg (50 C post-cure) °C Tensile strength MPa 447 85 83 188 86 74

RIFT vacuum forming • Known as – DRDF: Double RIFT Diaphragm Forming, or – RIDFT: Resin Infusion between Double Flexible Tooling • dry fabric is placed between two elastomeric membranes; • resin is infused into the fabric; • the ‘sandwich’ is vacuum-formed over the mould shape.

RIFT vacuum forming RIDFT image from JR Thagard, Ph. D thesis, Florida State University, 2003.

RIFT with flow medium RIFT 2 of 4 • A high permeability fabric allows resin to flood one surface followed by through-thickness flow KEY Resin feed Vacuum Reinforcement Flow medium • commonly referred to as either: – V(A)RTM • Vacuum (assisted) resin transfer moulding – SCRIMPTM • Seeman Composites Resin Infusion Manufacturing Process • patented in the USA but prior-art exists in Europe

Princess Yachts • Infusion of 42 -foot and 75 -foot boat hulls • http: //www. tech. plym. ac. uk/sme/mats 324/Video/PYinfusion. wmv

EADS VAP® process Membrane = Gore Composite Manufacturing Membrane (GCM) Image reproduced with permission from EADS

2 m diameter CFRP sonar dome • non-crimp carbon fibre fabric monolithic composite • from 9 mm to 50 mm thick, Vf = 60%, Vv = negligible

CFRP catamaran forward beam 60 v/o NCF (6000 x 300 x 50 mm) Manufactured by Julian Spooner Channel section to form box with a second joggled moulding - integral top hat supports Web: 600 gsm triax / 9 mm balsa / 600 gsm carbon triax Flanges: 600 gsm triax / 4 mm UD / 600 gsm triax Sicomin SR 8100 resin system Layup: 7 man hours, Infusion: 25 minutes, 20ºC / 20 m. B Postcure: 10 h @ 50ºC

Manufactured by the SCRIMPTM process J-boats Poma-Otis mass transit Images from www. tpicomp. com Reitnouer flat bed trailer NABI 30 -foot bus

Benefits of SCRIMPTM • Vosper Thornycroft state: • resin infusion into tows is independent of fabric weight. • reduced costs and greater efficiency in production: fewer layers of heavier fabric compared to 35 separate plies of 800 gsm woven roving glass used in hand lamination. • reduced component weight (up to 72% fibre by weight). • void content down from 5% by HL to <1% by SCRIMPTM. • increased laminate strength due to the higher fibre fraction and reduced void content. • reduced styrene emissions and waste resin.

The NEG-Micon 40 m radius AL 40 carbon-wood epoxy wind turbine blade Resin infusion manufacturing process developed with ACMC

Advanced Composite Armoured Vehicle Platform (ACAVP) • demonstrator manufactured by “VARTM” • reinforcement is quasi-isotropic non-crimp E-glass fabric • bare hull weight is around 6000 kg Image from http: //www. janes. com/defence/land_forces/news/jdw 010312_3_n. shtml

Civil engineering structures • DML Composites rehabilitate fractured structures for London Underground

CFRP infusion vs welded steel repair • London underground – ~£ 40 K/day lost revenue for closing the line between two stations • Offshore exploration and exploitation – ~£ 500 K/day of crude oil through small platform – need to drain down before hot work (welding)!

Resin Film Infusion (RFI) RIFT 3 of 4 • B-stage “prepreg” resin film without fibres • interleaved with reinforcement or grouped film layers in dry laminate KEY Reinforcement Vacuum Resin film • unlike prepreg, there air channels within the bagged laminate

RFI (RIFT 3) for aerospace • T-beams, aileron skin, swaged wing rib, three-bay box – Kruckenberg et al , SAMPE J, 2001 • fuselage skin panel for the Boeing 767 aircraft was moulded as a demonstrator with integral stiffeners – Cytec 5250 -4 RTM bismaleimide resin (100 m. Pa. s at 100°C) – 880 x 780 mm woven 5 -axis 3 -D fabric preform – Uchida et al , SAMPE J, 2001 • fuselage panels in TANGO Technology Application to the Near-term business Goals and Objectives of the aerospace industry – skins will be non-crimp fabric preforms – integrated stringers to be triaxial braids with unidirectional fibres – Fiedler et al, SAMPE J, 2003

“Semi-preg” infusion RIFT 4 of 4 • fabric partially pre-impregnated with resin KEY Reinforcement Vacuum Resin stripes • Commercial systems include – Advanced Composites Group ZPREG • resin stripes on one side of fabric – Cytec Carboform • resin impregnated random mat between the two fabric layers – SP Systems SPRINT®: SP Resin Infusion New Technology • resin between two fabric layers

Comparisons (debateable) In-plane Material costs £€$ Consumables £€$ Flow medium £€$ £€$ RFI £€$ £€$ Semi-preg £€$ £€$ £€$ Process time Quality

Summary • reviewed the four major variants of the Resin Infusion under Flexible Tooling process. • considered the application of these techniques to the manufacture of large composite structures. • recommend this route for the manufacture of large composite structures.

ACKNOWLEDGEMENTS • • • Higher Education Funding Council of England (HEFCE) Development of Research for funding early research into resin infusion Christopher Williams and Jim Craen for their respective contributions to the project. David Cripps at SP Systems Limited for most helpful discussions of an earlier version of this paper. Paul Hill at DML Composites for permission to use his Figure. Use of trade names/trade marks in the text of this chapter does not imply endorsement by the authors of any specific product. Such descriptions are provided simply in the interest of traceability.

Publication The text of this presentation has been refereed and is published in • Proceedings of the Institution of Mechanical Engineers Part L - Journal of Materials: Design and Applications, February 2005, volume L 219(1), 45 -58.

Based on earlier Power. Point • by John Summerscales and TJ Searle “Low pressure (vacuum infusion) techniques for moulding large composite structures” • by John Summerscales “A taxonomy for resin infusion” previously presented at: • Universiti Putra Malaysia, Bangi, Sept 2004 • Imperial College London, Dec 2004 • SAMPE out-of-autoclave symposium, Feb 2005 • Forum for Plastkompositter – Norway, Nov 2005 • Composite Innovations – Barcelona, Oct 2007 • ICMAC – Belfast, March 2009 • RINA – London, February 2010

. . to contact me Dr John Summerscales < jsummerscales@plymouth. ac. uk : http: //www. plymouth. ac. uk/staff/jsummerscales * School of Engineering Reynolds Building RYB 008 University of Plymouth Devon PL 4 8 AA England ) 01752. 5. 86150 2 01752. 5. 86101