JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 42

design
designs that closely mirror metallic parts, together with assembly methods that are also similar to those for metallic structures (the so-called “black aluminium” approach). Prepreg lay-up based on labour-intensive methods is also still widely used. Aerospace manufacturers are actively researching improved automation methods, alternate manufacturing methods, new structural material forms and increased part integration to lower composite manufacturing costs and improve their market competitiveness. They are not always aware of the fact that these cost reductions may require changes in both design and design rules, constraints and procedures. The cost of these procedural changes is difficult to predict in advance, but should form part of the overall cost estimation for any new manufacturing approach. Together with the rest of the aircraft industry, Israel Aerospace Industries (IAI) has been actively pursuing methods to reduce the cost of composites manufacturing. In the course of this effort, many changes in procedures were required due to design changes.

Fig. 1: Composite parts in the Gulfstream/IAI G280

Low-cost manufacturing development
IAI’s efforts to reduce composites manufacturing costs started about ten years ago. An early example was the development of an infusion technology for the manufacture of major UAV structures [1]. IAI has more than 30 years operational experience with UAVs, mostly using manual wet lay-up to manufacture their 100% composite structure. The incentive for using infusion methods was clear: they can use the same fabric and resin systems as wet lay-up at identical or lower cost, with improved property consistency and reduced weight. The resin infusion technology was further developed and applied to business jet semi-structural parts, replacing autoclave-cured honeycomb-cored, prepreg-skinned sandwich parts [ 2]. In addition to the infusion technology, computer- aided techniques for resin flow simulation, robotic preform manufacture and automated part trimming were introduced to further reduce costs [3]. This was developed further by incorporating non-crimp fabrics (NCF) in infused components for a subsequent business jet [4], and in an integrally-stiffened wing rib prototype with no detail part sub-assembly for the EC ALCAS programme [5]. The same NCF and resin material systems were also used for the manufacture using resin transfer moulding (RTM) of a one-piece integral rudder, again with little downstream detail part assembly, for a business jet [6]. This development exploited the experience gained with integral wing ribs using NCF designed and manufactured using RTM for the EC TANGO programme [ 7]. This development of liquid composite moulding methods was paralleled by improvements to composite manufacture by prepreg/autoclave methods. Early business jets versions used different prepregs, adhesives and other materials

for various composite parts, which complicated material procurement, storage and handling, and predominantly the hand lay-up method. In more recent business jets with a higher number of composite parts (as in Fig. 1), the materials used were consolidated to only one of each type, simplifying manufacturing logistics significantly. Together with the introduction of automated lay-up techniques, this assisted in cost reduction [8]. Further improvements accrued from the implementation of DFMA (Design For Manufacture and Assembly) methods, that reduced part count, and the design of large structures with high levels of structural integration eliminating many assembly processes [ 9,10]. It should be underlined that cost reduction solutions are highly dependent on aircraft size and production rates. An optimal solution for a large aircraft might not be appropriate, in terms of cost and weight, for a smaller aircraft due to design and manufacturing constraints. While significant manufacturing cost reductions have resulted from these developments, unanticipated changes in methods and procedures were sometimes necessary. Some examples are described in the following sections.

Thick ply reinforcements
The use of NCF multi-axial fabrics, in which aligned unidirectional fibre layers are stitched together, yields many structural and cost advantages. Compared to woven fabrics, NCF fabrics have excellent stiffness and strength properties due to minimal fibre crimp. The multi-axial plies minimize lay-up time, and NCF often use carbon fibre types (typically 12k tow) that are less expensive than those commonly used for prepregs or conventional woven fabrics (3k and 6k tows). However, this attractive picture is complicated by technical problems encountered during part design and development. Typical plies are thicker than in conventional prepreg and fabrics. 0/90 layers – or combinations such

42 jec composites magazine / No74 July 2012



JEC COMPOSITES MAGAZINE - Issue #74 - July 2012

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #74 - July 2012

Cover
Edito
Point of view: Closer to the shop floor
Contents
Agenda of Events
COMPANY & BUSINESS
- In Brief
- Glass fibre
APPLICATIONS
- Pipes & tanks
- Building
MARKET
- Human resources
- Glass fibre
- Turkey
FEATURE AUTOMOTIVE
- Braiding
- Lightening
- D-LFT
- Sustainability
- RTM
- RIM
RESEARCH & DEVELOPMENT
- Design
- Fatigue behaviour
TECHNOLOGY & INNOVATIONS
- Wind
- Reinforcement
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - Cover
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 2
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - Edito
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - Point of view: Closer to the shop floor
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 5
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - Contents
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 7
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - In Brief
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Glass fibre
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 11
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 12
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Pipes & tanks
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Building
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 15
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 16
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 17
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Human resources
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Glass fibre
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 20
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 21
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Turkey
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 23
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Braiding
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 25
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Lightening
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 27
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 28
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 29
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - D-LFT
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 31
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 32
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 33
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Sustainability
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 35
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 36
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - RTM
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 38
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 39
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - RIM
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Design
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 42
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 43
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 44
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 45
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Fatigue behaviour
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 47
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 48
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 49
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 50
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Wind
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 52
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 53
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - - Reinforcement
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 55
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 56
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - Index
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - In the world
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 59
JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 60
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