Integration and Pixel Mechanics Progress

1. Integration and Pixel MechanicsProgress 27-April 2011 HFT Mechanics Meeting E Anderssen, LBNL

2. Pixel Carriage • Test Stand for Carriage Insertion ‘F’-shaped supports part of ‘Box’ in which detector will be delivered • Compliance added to bottom rail bearings—allowing for rail misalignment—here about 300microns.

3. Parts are Symmetric (common) • Carriage is rotationally symmetric about STAR Coordinates • Same component parts can be used for the North or South Detector halves • Same is true for ‘F’ Stands • Only difference is how parts are assembled, i.e. the ‘Top’ Rail on both sides remains the ‘Top’ • Compliance mentioned on previous slide only for ‘Bottom’ rail • Means there are no ‘mirror’ parts between Pixel Halves, only assembly variations

4. Hinge Assembly Installed • Hinge provides DOF allowing PXL to articulate around Large Beampipe and close in around Be Beampipe • Swings thru motion nicely—no rattle or slop in motion • Left Picture shows outer-most position to clear BP flanges • Right shows full range of motion inward—not this much is required, exaggerated to show DOF

5. D-Tube Mounted on Hinge • D-Tube not bonded together yet (happens today) • Held together with tape to check dimensions • Service burden similar in volume to detector—will look at handling as part of this effort

6. PXL Sectors Mounted on D-Tube • Only mounted 2-sectors as D-Tube is only *taped* together • Will pull out 5-sectors after D-Tube is bonded • General comment is they seem to line up well with rails, even for something taped together… (parts fit well)

7. Other Side

8. D-Tube Assembly • Ready for Bonding—shown in bond fixture; just need to get to it • T-Slots for locating Kinematic Mounts, again symmetric, but ‘Top’ remains reference between North/South

9. Sector Mount Plate • Dovetail mounts on ends of sectors slide into these positions • Central one used to locate sectors relative to Kinematic Mounts in same fixture • Fixture Machined by UTA, parts fit nicely • Small problem with machining of Dovetail plate in bond area—complicated transition area • Rectified with a rat-bastard on prototypes—will be programmed in for production CNC • Still need to bond—just need to get to it…

10. WSC Mandrel • Mandrel and Cart delivered late March just before review • QC indicates the mandrel is 125microns oversize on Dia.* • Varies less than 25microns along length which is about our repeatability with a Pi-Tape…

11. Autoclave Thermal Tests • The WSC mandrel was run alone with several thermocouples to assess thermal performance • Autoclave has a ducted internal flow of about 2000cfm recirculated via the bottom chordal duct and distributed by baffles in the door and back • Studies with tool position and some internal added baffles lead to an optimal performance (all TC’s within 10F during temp-ramps) (not shown in plot above which was 1st run)

12. Fabrication Process Overview • Composite materials in our application come pre-impregnated with a tightly controlled resin content • Layers of this material, with specific fiber orientation, are laminated together under pressure and heat which cures the resin system, and yields a composite laminate • A ‘Layer’ is composed of ‘Plies’ which are discrete shapes of the pre-preg material with specific fiber orientation • A ‘Lay-up’ is the physical deposition of the plies with accurate positions and orientations to build-up the component laminate (also a noun referring to the pre-cured part amid-fabrication) • The impregnated fibers have ‘tack’ (tackiness) which allows a ply to ‘stick’ in position when placed (depends on resin content/temp) • Pressure (compaction) is required at various stages of fabrication, generally applied by vacuum bag after manual pressure (squeegee) • Compaction is required first to adhere a ply to plies in previous layers via ‘tack’, then to remove entrained air in the ply-stack • During cure Compaction is required to exceed the vapor pressure of water and other entrained volatiles to avoid void nucleation

13. Test Shell Production—Ply Cutting • Test laminates are required to verify the fabrication procedure and tooling--3-4 test laminates are required • Approx 50 linear meters of material is used in each test • Plies are cut using an automated ply cutter with auto-feed

14. Ply Stack wrapping on Mandrels • Example from ATLAS—ignore fiber orientations • Ply stacks are ‘bricked’ to provide overlaps in plies between layers, so gaps are bridged by continuous fibers • Staggers and Offsets in Z and phi are required

15. Pre-Compacted Ply Stacks • Using mechanical (window) templates registered to pins (black buttons in picture), plies are stacked and compacted • Fiber orientation per-layer is important; using precision cut plies and mechanically registered placement assures quality

16. Ply-Stack Application to Tool (Mandrel) • Pre-Compacted (flat) ply-stacks allow for more rapid and accurate deposition of material • A mechanical guide, registered to the Mandrel axis and pre-aligned allows accurate placement • No overlaps are allowed, gaps up to 1mm are tolerable • Flat pre-compaction can lead to some problems • Inner-plies when bent around mandrel go into compression • Careful attention to tension and order is required to prevent fiber buckling on vacuum compaction

17. Base-Stack on Mandrel • Previous slide showed application of outer stack on this one • Base Stack sequence most important—plies in Hoop direction most prone to buckling • Circular constraint susceptible to external pressure…

18. First Prototype Shell • Generally successful, but inner hoop plies fail (buckle/wrinkle) during pre-cure compaction on mandrel • Uncomfortable with hoop ply failures, but likely acceptable • On the plus side Outside Diameter is 400.1mm* (400mm Nom)

19. Shell Prototype Efforts • First Prototype was ‘acceptable’ but looking for methods to avoid fiber buckling during mandrel application/compaction • Second Prototype planned independent application of first Hoop ply (there are 2) • Second Prototype effort spanned weekend—flat stack with second hoop ply pre-compacted on Friday • ‘Flat’ compacted stacks exhibited fiber buckling in hoop ply • ‘Bubbles’ coalesce to high curvature regions under a compliant vacuum bag • Inclusion of ‘caul plate’ under vacuum bag distributes pressure allowing relaxation of high curvature regions • Current plan is independent application of each hoop layer separately, only pre-compacting oriented plies

20. Hoop Layers • ‘Hoop’ plies have fibers oriented in phi-direction—most susceptible to buckling under external pressure • Chose to apply ‘Hoop’ plies independent from Base Stack • Allows greater tension and compaction on tool surface • Removes concern about compression from bending of flat stack onto mandrel • Note that Mandrel expands 1.8mm during cure, ~6mm circumference • Wrinkles/Buckling on finished product unlikely—only occurs during Lay-up—difficult to avoid

21. IDS Cone Prototype • Paper templates of ply shapes were generated to study the formability of the shapes • These have been iterated and the final trial lay-up on the cone tool tested to verify gaps and assure no-overlaps

22. Cone Ply Shapes Verified • Paper is a conservative analog for non-formable surfaces • Cone is fabricated from cloth-prepreg—forgiving in shear • Program for ~250 unique plies programmed into ply-cutter for 24 layers plus pad-up at flanges • Will cut ~12m^2 of fiber today