JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 66
thermoplastic
Fig. 9: External Radius vs. Stringer Load Capability
Fig. 11: Stringer Yield Load Capability vs. Thickness
Test data indicate a yield strength increase of 34 % to 41 % by reducing the external radius from 4.3 mm (0.17 in) to 2.5 mm (0.10 in). While these results are promising, the strength improvement is limited by a quickly shrinking internal radius. The problems with too small an internal radius are discussed in the next section below. Add plies Adding global plies to a stringer is simple but heavy. Adding local padup plies is more efficient, and with advanced forming techniques, it is possible to form stringers with internal radii as small as 0.25 mm (0.010 in) with AS4/PEEK and the Fiberforge process. Figure 10 shows a micrograph of a stringer successfully formed with a 0.25-mm (0.010 in) internal radius. No voids, porosity or broken fibres are visible.
as a function of thickness for a stringer with an external radius of 4.3 mm (0.17 in). Adding plies does not increase yield past a point due to early buckling of the inside ply. Increasing external radius in order to accommodate more plies may be limited by interface requirements. Metallic fittings and radius filler If radius-crushing loads cannot be met by strengthening the stringer internally through either of the methods previously discussed, then external reinforcements are required.
Fig. 12: External Reinforcements for Stringer Radii
Fig. 10: Micrograph of 0.25 mm (0.010 in) Internal Radius Stringer
Figure 12 illustrates several methods of externally reinforcing stringers for crush strength, including metallic flange support fittings, clips and radius fillers. Novel idea for crush-resistant stringers A novel approach for increasing radius-crush capability is to implement a tight external radius while maintaining a reasonable internal radius. The more direct compression load path results in significant reduction to the fibre and matrix stresses, and the yield failure modes are suppressed. The stringer carries load to ultimate without premature yielding. Figure 13 illustrates a basic stringer with a constant-thickness corner (left) next to a novel stringer with R = r = 1.5 mm (0.06 in) resulting in a variable-thickness corner (right).
Extremely tight radii are generally avoided, however. A rule-ofthumb for aerospace structures is: r ≥ 2t + 0.76 mm [1, 2] where r = internal radius (mm) and t = laminate thickness (mm). While this rule is primarily geared towards radii with both opening moments, there are limits to closing moment cases below. Figure 11 shows the stringer yield load capability
66 jec composites magazine / No76 October - November 2012
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012
Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012
Cover
Edito
Point of view: high-perfomance
Contents
COMPANY & BUSINESS In Brief
APPLICATIONS
- Bicycle
- Kayak
- Urban car
MARKET
- Human resources
- Aramid & basalt
SPECIAL JEC AMERICAS
- Floorplan
- 6th I.C.S.
- Academics posters area
- Awards
- Eductation & Skills
- Innovations Report & News
- Moulding
- Injection
- Defense
- CNC
- Land transportation
RESEARCH & DEVELOPMENT
- Thermoplastic
- Tape placement
- Cost effectiveness
TECHNOLOGY & INNOVATIONS
- Out-of-autoclave
- CFRC
- Software
Agenda of Events
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - Cover
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 2
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - Edito
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - Point of view: high-perfomance
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 5
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - Contents
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 7
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 8
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 9
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - COMPANY & BUSINESS In Brief
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 11
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Bicycle
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 13
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 14
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Kayak
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Urban car
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 17
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 18
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 19
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Human resources
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 21
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Aramid & basalt
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 23
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 24
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 25
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 26
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - SPECIAL JEC AMERICAS
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Floorplan
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 29
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 30
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - 6th I.C.S.
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 32
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 33
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 34
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 35
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Academics posters area
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 37
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Awards
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 39
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 40
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 41
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Eductation & Skills
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 43
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Innovations Report & News
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 45
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 46
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 47
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 48
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 49
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Moulding
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 51
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 52
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Injection
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 54
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 55
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Defense
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 57
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - CNC
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 59
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Land transportation
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 61
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 62
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Thermoplastic
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 64
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 65
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 66
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 67
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 68
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 69
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Tape placement
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 71
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 72
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 73
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Cost effectiveness
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 75
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 76
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 77
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 78
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 79
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 80
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Out-of-autoclave
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 82
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - CFRC
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 84
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 85
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - - Software
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 87
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - Index
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - In the world
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 91
JEC COMPOSITES MAGAZINE - Issue #76 - October/November 2012 - 92
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