JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 44

design
pultrusion process can only produce straight profiles with a constant cross section. This means that pultrusion cannot be used for typical wing or stabilizer spars, since these usually have a tapered shape. Its application to stringers for stiffened skins (e.g., T or Z shapes) is limited to surfaces that have straight ruled surfaces. An attempt to use pultrusion to produce stringers for a typical aerodynamic surface (wing or stabilizer skins) will require a converging layout, since parallel lines on the surface are not straight. This results in a sub-optimal design from a weight aspect. Theoretically, pultrusion can be used for fuselage stringers, except in the rear sections where curved stringers are required. However, this application has additional limitations. Besides the high impact resistance required for the fuselage skin, the fuselage stringers usually require local cross section changes, such as “duck feet” near frame attachments, which cannot be achieved using pultrusion (unless a large section is removed by machining on most of the length, which is clearly not economical). Another issue arises at part ends, such as production breaks, or other main joints. The classical design of this critical detail usually involves increasing the skin thickness, and having the stringer “climb” (joggle) on this thickness variation (Fig. 3). This too cannot be achieved using conventional pultrusion. Methods are being developed to allow post-forming of pultruded parts that could, in principle, accommodate joggled designs, but these are not yet commercial. This issue can be resolved by novel designs of this detail but this requires an additional effort to verify the integrity of these new concepts in the development stage. In any event, despite these limitations, the economic potential for pultrusion is so attractive that there is a substantial motivation for using it. the honeycomb core cells fill with resin during the process. The usual solution consists in using closed-cell polymeric foam cores for sandwich structures. These cores are more costly than honeycombs, and they tend to absorb resin at the interface, which increases the product weight. Initial designs with these cores used the same edge bevel angles as defined for honeycomb cores in co-cured prepreg skin autoclave manufacture. With this bevel angle, it was impossible to prevent ply bridging at the base of the bevelled section in any part geometry more complex than a single edge on a flat plate. The solution was to change the core bevel angle rules to provide a more gradual slope at core edges. This was particularly important for the radiused corners of cores in bi-curved part geometries.

Lay-up automation
The introduction of automated tape laying systems has generated cost savings due to shorter manufacturing times and the reduced amount of skilled manual labour required for the overall lay-up process. Automated lay-up improves directional repeatability and reduces raw material waste. It also opens new fibre steering possibilities, allowing a higher degree of structure optimization. However, it is important to note that incorporating automated machines for ply lay-up involves new design rules too. Some machines have certain limitations that affect the design. Tape laying equipment is limited in capability due to the dimensions of the machine, in particular the tape laying head. The head’s degrees of freedom of movement and absolute dimensions restrict the part geometries that can be designed. Moreover, the prepreg tapes used in automated methods are usually narrower than those used for manual lay-up. A laminate produced with automated methods will contain more splice areas than a manually produced one. This reduces mechanical properties due to the resulting restriction of the fibre volume fraction. With automated methods, the lay-up accuracy is such that the permissible lay-up discrepancies that were historically specified for manual lay-up methods do not apply. The use of automated lay-up systems requires the generation of new misalignment, gap and overlap limits specific to the manufacturing technique.

Sandwich core design
It is well known that honeycomb cores cannot be used in liquid composite moulding processes. Unless the core is encapsulated (which is problematic for infusion processes),

Certification
The aircraft certification process is a major issue for all new technologies. Certification authorities are by nature very conservative, and correctly so. The introduction of new technology involves increased efforts to certify the structure since certification authorities are more cautious and certification requirements stricter than with proven technologies. For any new type of material, process or structure, it is essential to involve certification authorities at an early stage of the development process. At this stage,

Fig. 3: Stringer end with pultrusion

44 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
https://www.nxtbook.fr/newpress/jeccomposites/jcm2107_141
https://www.nxtbook.fr/newpress/jeccomposites/jcm2105_140
https://www.nxtbook.fr/newpress/jeccomposites/jcm2103_139
https://www.nxtbook.fr/newpress/jeccomposites/jcm-experts-digest-additive-manufacturing-2020
https://www.nxtbook.fr/newpress/jeccomposites/jcm2101_138
https://www.nxtbook.fr/newpress/jeccomposites/jcm2011_Special_Issue4
https://www.nxtbook.fr/newpress/jeccomposites/jcm2011_137
https://www.nxtbook.fr/newpress/jeccomposites/jcm2009_136
https://www.nxtbook.fr/newpress/jeccomposites/jcm2007_135
https://www.nxtbook.fr/newpress/jeccomposites/jcm_2020_Q1_Innovation_Report
https://www.nxtbook.fr/newpress/jeccomposites/jcm2005_Special_Issue3
https://www.nxtbook.fr/newpress/jeccomposites/jcm2005_134
https://www.nxtbook.fr/newpress/jeccomposites/jcm2003_133
https://www.nxtbook.fr/newpress/jeccomposites/jcm2001_132
https://www.nxtbook.fr/newpress/jeccomposites/jcm1911_Special_Issue2
https://www.nxtbook.fr/newpress/jeccomposites/jcm1911_131
https://www.nxtbook.fr/newpress/jeccomposites/jcm1909_130
https://www.nxtbook.fr/newpress/jeccomposites/jcm1907_129
https://www.nxtbook.fr/newpress/jeccomposites/jcm1905_128
https://www.nxtbook.fr/newpress/jeccomposites/jcm1903_Special_Issue1
https://www.nxtbook.fr/newpress/jeccomposites/jcm1903_127
https://www.nxtbook.fr/newpress/jeccomposites/jcm1901_126
https://www.nxtbook.fr/newpress/jeccomposites/jcm1811_125
https://www.nxtbook.fr/newpress/jeccomposites/jcm1810_124
https://www.nxtbook.fr/newpress/jeccomposites/jcm1808_123
https://www.nxtbook.fr/newpress/jeccomposites/jcm1807_122
https://www.nxtbook.fr/newpress/jeccomposites/jcm1805_121
https://www.nxtbook.fr/newpress/jeccomposites/jcm1804_120
https://www.nxtbook.fr/newpress/jeccomposites/jcm1803_119
https://www.nxtbook.fr/newpress/jeccomposites/jcm1802_119-Supplement_Innovation_Report
https://www.nxtbook.fr/newpress/jeccomposites/jcm1801_118
https://www.nxtbook.fr/newpress/jeccomposites/jcm1711_117
https://www.nxtbook.fr/newpress/jeccomposites/jcm1710_116
https://www.nxtbook.fr/newpress/jeccomposites/jcm1708_115
https://www.nxtbook.fr/newpress/jeccomposites/jcm1707_114
https://www.nxtbook.fr/newpress/jeccomposites/jcm1706_113
https://www.nxtbook.fr/newpress/jeccomposites/jcm1704_112
https://www.nxtbook.fr/newpress/jeccomposites/jcm1703_111
https://www.nxtbook.fr/newpress/jeccomposites/jcm1701_110
https://www.nxtbook.fr/newpress/jeccomposites/jcm1611_109
https://www.nxtbook.fr/newpress/jeccomposites/jcm1610_108
https://www.nxtbook.fr/newpress/jeccomposites/jcm1608_107
https://www.nxtbook.fr/newpress/jeccomposites/jcm1607_106
https://www.nxtbook.fr/newpress/jeccomposites/jcm1605_105
https://www.nxtbook.fr/newpress/jeccomposites/jcm1604_104
https://www.nxtbook.fr/newpress/jeccomposites/jcm1603_103
https://www.nxtbook.fr/newpress/jeccomposites/jcm1601_102
https://www.nxtbook.fr/newpress/jeccomposites/jcm1511_101
https://www.nxtbook.fr/newpress/jeccomposites/jcm1510_100
https://www.nxtbook.fr/newpress/jeccomposites/jcm1509_99
https://www.nxtbook.fr/newpress/jeccomposites/jcm1507_98
https://www.nxtbook.fr/newpress/jeccomposites/jcm1505_97
https://www.nxtbook.fr/newpress/jeccomposites/jcm1504_96
https://www.nxtbook.com/newpress/jeccomposites/jcm1503_95
https://www.nxtbook.com/newpress/jeccomposites/jcm1501_94
https://www.nxtbook.com/newpress/jeccomposites/jcm1412_93
https://www.nxtbook.com/newpress/jeccomposites/jcm1410_92
https://www.nxtbook.com/newpress/jeccomposites/jcm1409_91
https://www.nxtbook.com/newpress/jeccomposites/jcm1406_90
https://www.nxtbook.com/newpress/jeccomposites/jcm1405_89
https://www.nxtbook.com/newpress/jeccomposites/jcm1404_88
https://www.nxtbook.com/newpress/jeccomposites/jcm1403_87
https://www.nxtbook.com/newpress/jeccomposites/jcm1401_86
https://www.nxtbook.com/newpress/jeccomposites/jcm1311_85
https://www.nxtbook.com/newpress/jeccomposites/jcm1310_84
https://www.nxtbook.com/newpress/jeccomposites/jcm1308_83
https://www.nxtbook.com/newpress/jeccomposites/jcm1307_82
https://www.nxtbook.com/newpress/jeccomposites/jcm1305_81
https://www.nxtbook.com/newpress/jeccomposites/jcm1304_80
https://www.nxtbook.com/newpress/jeccomposites/jcm1303_79
https://www.nxtbook.com/newpress/jeccomposites/jcm1301_78
https://www.nxtbook.com/newpress/jeccomposites/jcm1212_77
https://www.nxtbook.com/newpress/jeccomposites/jcm1210_76
https://www.nxtbook.com/newpress/jeccomposites/jcm1208_75
https://www.nxtbook.com/newpress/jeccomposites/jcm1207_74
https://www.nxtbook.com/newpress/jeccomposites/jcm1206_73
https://www.nxtbook.com/newpress/jeccomposites/jcm1204_72
https://www.nxtbook.com/newpress/jeccomposites/jcm1203_71
https://www.nxtbook.com/newpress/jeccomposites/jcm1201_70
https://www.nxtbook.com/newpress/jeccomposites/jcm1111_69
https://www.nxtbook.com/newpress/jeccomposites/jcm1110_68
https://www.nxtbook.com/newpress/jeccomposites/jcm1108_67
https://www.nxtbook.com/newpress/jeccomposites/jcm1107_66
https://www.nxtbook.com/newpress/jeccomposites/jcm1105_65
https://www.nxtbook.com/newpress/jeccomposites/jcm1104_64
https://www.nxtbook.com/newpress/jeccomposites/jcm1103_63
https://www.nxtbook.com/newpress/jeccomposites/jcm1101_62
https://www.nxtbook.com/newpress/jeccomposites/jcm1011_61
https://www.nxtbook.com/newpress/jeccomposites/jcm1010_60
https://www.nxtbook.com/newpress/jeccomposites/jcm1009_59
https://www.nxtbook.com/newpress/jeccomposites/jcm1006_58
https://www.nxtbook.com/newpress/jeccomposites/jcm1005_57
https://www.nxtbook.com/newpress/jeccomposites/jcm1004_56
https://www.nxtbook.com/newpress/jeccomposites/jcm1003_55
https://www.nxtbook.com/newpress/jeccomposites/jcm1001_54
https://www.nxtbook.com/newpress/jeccomposites/jcm0911_53
https://www.nxtbook.com/newpress/jeccomposites/jcm0910_52
https://www.nxtbook.com/newpress/jeccomposites/jcm0909_51
https://www.nxtbook.com/newpress/jeccomposites/jcm0907-08_50
https://www.nxtbook.com/newpress/jeccomposites/jcm0906_49
https://www.nxtbook.com/newpress/jeccomposites/jcm0904_48
https://www.nxtbook.com/newpress/jeccomposites/jcm0903_47
https://www.nxtbook.com/newpress/jeccomposites/jcm0901_46
https://www.nxtbook.com/newpress/jeccomposites/jcm0811_45
https://www.nxtbook.com/newpress/jeccomposites/jcm0810_44
https://www.nxtbook.com/newpress/jeccomposites/jcm0809_43
https://www.nxtbook.com/newpress/jeccomposites/jcm0807_42
https://www.nxtbook.com/newpress/jeccomposites/jcm0806_41
https://www.nxtbook.com/newpress/jeccomposites/jcm0805_40
https://www.nxtbook.com/newpress/jeccomposites/jcm0803_39
https://www.nxtbook.com/newpress/jeccomposites/jcm0801_38
https://www.nxtbook.com/newpress/jeccomposites/jcm0712_37
https://www.nxtbook.com/newpress/jeccomposites/jcm0710_36
https://www.nxtbook.com/newpress/jeccomposites/jcm0709_35
https://www.nxtbook.com/newpress/jeccomposites/jcm0707_34
https://www.nxtbook.com/newpress/jeccomposites/jcm0706_33
https://www.nxtbookmedia.com