Trans RINA, Vol 152, Part B1, Intl J Small Craft Tech, 2010 Jan-Jun REPAIR TECHNOLOGY FOR THERMOPLASTIC COMPOSITE BOATS


M E Otheguy and A G Gibson, Newcastle University, UK E Findon and R M Cripps, BVT Surface Fleet Ltd., UK (DOI No: 10.3940/rina.ijsct.2010.b1.101)


SUMMARY


This paper describes research on the repair of thermoplastic composite boats. The work was carried out because the viability of the thermoplastic composite option for boat construction depends critically on the availability of a simple repair method. An experimental thermoplastic composite rigid inflatable boat (RIB), built by BVT Surface Fleet was subjected to controlled impact damage. Ultrasonic non-destructive testing was used to characterise the extent of the resulting damage area. An emergency repair technique involving the replacement of the damaged material by a fusion bonded composite patch, was developed. The procedure involved simple, easily portable equipment and avoided the use of a mould. A micrography study, accompanied by tensile tests, demonstrated that the technique provided a watertight repair of the required structural integrity.


1. INTRODUCTION


This paper relates to damage and repair issues associated with an 8.5m long experimental


rigid inflatable boat


(RIB), manufactured in thermoplastic composite to demonstrate the viability of thermoplastics technology in marine composites.


Thermoset-based composite materials have become dominant, over five decades of evolution,


in both


military and leisure boatbuilding, mainly due to their ease of construction, aesthetic characteristics, low weight and excellent mechanical properties [1]. Composite- metal hybrid structures have also been investigated for defence applications [2]. The boatbuilding field, however, has recently entered a further period of rapid change driven by the need for cleaner, more sustainable and more efficient


processes, which has led to a


movement away from open mould processes towards closed mould ones. There has also been widespread interest in the replacement of thermoset technology by thermoplastic composites.


In addition to the need for clean and quick processing, the interest in thermoplastic matrices has arisen due to the potential for recyclability and the possibility of greatly improved toughness [3-10]. The recyclability issue has only recently been practically examined [14] and it has been demonstrated that the hull structure of the thermoplastic RIB is indeed recyclable, by granulation and melt processing into a useful injection moulding material. These reasons led the Royal National Lifeboat Institution (RNLI) to order an experimental Atlantic 85 RIB to be built in glass reinforced polypropylene (PP- glass). The boat was successfully manufactured in 2004 by BVT Surface Fleet (formerly VT Halmatic). Its thermoset production sister boat is shown in Figure 1.


The purpose of because the


restoration


this study was to investigate repair, of functionality following


damage is a key requirement of any boat construction technology.


2. Figure 1: Atlantic 85 RIB. EXPERIMENTAL 2.1 DAMAGE EVENT


The main structural material used in the experimental Atlantic 85 was Twintex T PP 60 woven PP-glass commingled fabric with and areal weight of 1,485 g/m2, containing 60 wt.% glass in the form of 18µm diameter fibres. The boat internal structure was a sandwich construction of the Twintex fabric and DIAB Pro-balsa Standard core material. The sandwich laminates employed various thicknesses and numbers depending on function and position.


of


The event chosen for the purpose of damaging the hull was a simulated grounding incident. It was assumed in the present


travelling at 10.25 knots (5.27 m·s-1), corresponding to a kinetic energy dissipation of 31.9 kJ. For the purpose of


case that the ©2010: The Royal Institution of Naval Architects B-33


Joining of thermoplastic composites could, in principle, be achieved by adhesive bonding, fusion bonding or mechanical fastening. Of these possibilities, fusion bonding, which is possible with thermoplastics but not thermosets, offers the greatest potential for a high strength, water-tight repair [11, 12].


plies,


2,300 kg hull would be


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