SAMPE Journal - March/April 2012 - (Page 7)

Feature Article Butt-joined, Thermoplastic Stiffened-skin Concept Development A. Offringa, J.W. van Ingen, A. Buitenhuis Fokker Aerostructures BV Hoogeveen, The Netherlands Email: Arnt.Offringa@fokker.com Abstract A novel thermoplastic skin concept, with co-consolidated stringers, is being brought to technology readiness level (TRL) 6. This implies manufacturing and mechanical testing of full scale demonstrator products. The stringers are T-shaped and made of flat preforms that are butt jointed to each other and to the panel skin. An injection molded filler increases strength. The skin is fiber placed over the stringer preforms and the product is co-consolidated at melt temperature. Because of the butt-joints, manufacturing is relatively simple. The result is a tough thermoplastic product that can compete on weight and cost with state-of-the-art thermoset composite panels. Development and testing of the panel concept is being done in a step-by-step process. Consecutive building blocks are: coupons, three-stringer subcomponent panels and finally full scale skin panels. The main panel represents the mid-section of a business jet horizontal tail. The panel will be assembled into a 12 meter span torsion box and tested in the second half of 2011. Introduction General Since first appearing on the market in the 1980’s, high-end thermoplastic composites have held promise for aircraft structure. High toughness and unique processing possibilities, such as pressforming and welding, have fueled this promise. Through the years, a growing amount of applications has appeared with OEM’s such as Airbus, Boeing and Gulfstream. Missing to date has been the step to truly large primary structure components. This step is currently being made through a dedicated effort. This article explains the development process towards this type of structure and in particular an ongoing process to obtain a certifiable large thermoplastic composite skin with butt-joined stiffeners. Current Thermoplastic Composite Applications As a result of nearly two decades of development, a growing number of products is currently manufactured and designed in thermoplastic composites. As a good example of the processing advantages of thermoplastics, large numbers of ribs and stiffeners are manufactured with the press-forming process. On the new 787 and Airbus A350, the extensive use of composites for fuselage has prompted the creation of large numbers of brackets, clips and cleats in thermoplastic. Figure 1 shows a press-formed stiffener by Dutch specialist manufacturer DTC. Further exploiting the processing flexibility of these materials, welded assemblies have been developed and matured. Examples are the glass/PPS wing fixed leading edge of the A380 aircraft (Figure 2,1) and the recently developed carbon/PPS rudder and elevators for the Gulfstream G650 business jet (Figure 3,2). A feature of both these leading edges and control surfaces is that they are post-buckled structures. This means that the design has a reduced weight due to a thin skin that is allowed to buckle during high load flight conditions. This type of design does require a large number of ribs, with a relatively small rib pitch. With traditional assembly techniques, this would result in high manufacturing cost. However, by using welding techniques, the cost is kept in check. The CETEX range of glass and carbon fiber reinforced fabric materials for these products have been developed by materials specialist TenCate. WE MOVED! Thermoplastic Growth Potential With a large portion of aircraft becoming composite structure, many opportunities are emerging for thermoplastics structure. Specific properties of thermoplastic composites provide this growth potential: •High toughness results in low weight designs and •Unique processing capabilities make for lower cost designs. Figure 1. Press-formed stiffener (photo courtesy DTC). SAMPE Journal, Volume 48, No. 2, March/April 2012 Figure 2. Welded thermoplastic wing fixed leading edge A380 (photo courtesy Airbus). 7

Table of Contents for the Digital Edition of SAMPE Journal - March/April 2012

SAMPE Journal - March/April 2012
Contents
President’s Message
Technical Director’s Corner
Butt-joined, Thermoplastic Stiffenedskin Concept Development
Perspectives
Europe News & Views
SAMPE Europe’s SEICO 2012, Paris
SAMPE Europe’s SEMAT 2012, Munich
The SAMPE Foundation
SAMPE Proceedings
Advanced Diaphragm Forming Process for High Temperature Thermoplastic Composite Applications
Perspectives
Materials & Products
SAMPE Books & CD’s Order Form
SAMPE LinkedIn Communities
SAMPE Journal Editorial Calender
Welcome SAMPE’s Newest Members
SAMPE Tech 2012 Call for Papers
Industry News
Corporate Partners
SAMPE 2012|Baltimore
SAMPE 2012 Exhibition
SAMPE 2013|Long Beach Call for Papers
Advertiser’s Index
Resource Center
Membership Application
Industry Events Calendar
Chapter Meetings Dates and Contacts

SAMPE Journal - March/April 2012

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