Shur-Lok Design Manual
Shur-LokDesign ManualFasteners for Sandwich Structure
TABLE OF CONTENTSPageSectionIINTRODUCTIONWhy Use Sandwich? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Sandwich Structure Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Methods for Joining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical Sandwich Panel Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2222DESIGN CRITERIATransmitting Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Consider the Design Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A Word About Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Load Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Tension Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Shear Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .457777IIIAPPLICATION METHODSMolded-In Inserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Installation Hole Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Mechanical Inserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Edge Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8899IVMATERIALSSelection of Potting Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Tailored Compounds Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Material Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101010TESTINGMethods of Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Recommended Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1112IIVVIFigure133456789101112131415TEST RESULTSScope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3LIST OF ILLUSTRATIONSPage2Typical Honeycomb Panel Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Solid Section Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Typical Load Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Fastener Inserts for Honeycomb Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Sandwich Panel Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Fastener Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Dimension Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Shur-Tab Potting Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Typical Core Undercut for Molded-In Insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Simple Mechanical Insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Shur-Torq Self-Retaining Mechanical Insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Step Drill Provides Two Hole Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S h e a r T e s t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Flatwise Tension Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Torque-Out Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Copyright 1996 by Shur-Lok Corporation
SHUR EFACEFasteners are as old as history itself. From the time thatprehistoric man first used vines and fibers to secure hiscrude shelters, the science of fastening has steadily evolveduntil today it ranks in importance with the mostsophisticated technical operations. Every advanced vehicle,every complex electronic device is largely, if not wholly,dependent on the integrity of its fasteners. Shur-LokCorporation, a pioneer and current frontrunner in the designand manufacture of specialty fasteners for industry,dedicates this document to a thorough comprehension ofthe selection of fasteners for sandwich structures, and totheir proper application.Towards this goal, it is important for the reader tounderstand the applications and configurations of sandwichcomposites themselves.1
SECTION — ISECTION 1 — INTRODUCTIONWHY USE SANDWICH?When design requirements demand superior strengthto-weight ratios, sandwich structure is indicated. Inaddition to its high strength, inherent rigidity and minimumweight, sandwich provides the desirable side benefits ofthermal and acoustical insulation.Sandwich, by its very nature, is generally used assheeting or flat panel form, applied to open framework as atransverse web to carry shear loading. In other applications,it acts as a support diaphragm. It serves as both a primaryand secondary load member. And, it is capable oftransmitting extremely high loads when properly attachedto the framework.Other applications take advantage of its favorably lowweight-to-area ratio. Typically, these include curtain wallsfor decoration or the baffling of sound and light. Suchapplications do not generally consider the inherent loadcapabilities of the structure.Initially sandwich was used only in flat panelapplications-a logical step away from plywood and othersheet panels. Recent improvements, however, in fabricationtechniques and growing industry awareness of sandwichpotential have spurred bolder forms. Today these includecompound curves, skeletonized sections and many complexshapes previously considered impossible.face sheets attached to an inner core material; the core ismade of hexagonal cells having walls perpendicular to thefacesheet planes (See Figure 1). Many materials have beenused successfully in honeycomb sandwich includingaluminum, steel, high-temperature alloys, paper, wood,fiberglass and plastics. In some applications honeycombcells are filled with a foam-in-place expanding plastic.Other forms of sandwich consist of face sheets bonded tohomogeneous cores such as foamed plastics or wood. Thevariety is limited only by the state of the art and theimagination of the designer.METHODS FOR JOININGRegardless of form, the methods for joining the twoface skins and inner core into a rigid member are numerous.SANDWICH STRUCTURE DETAILSThe principal form of sandwich structure is thehoneycomb configuration. This consists of top and bottom2Figure 1 — Typical Honeycomb Panel Construction
SHUR LOKCBy far the most widely used is that of adhesives applied byany of several techniques, and activated chemically orthermally.1. One method consists of brushing or spraying theadhesive film over one surface, and subsequentlymating with the second part precoated withactivator.2. A second approach use prefabricated sheetadhesive. Adhesive, rolled into a thin sheet partiallycured to retain form, is stored between temporarynon-adhering film, ready for use.3. Another bonding technique consists of applying theadhesive with rollers to a scrim or grid cloth, whichis then cut to size and applied between core andface skins.4. Still another method simply calls for an evencoating of adhesive on the face skin, which issubsequently activated and applied before setup.In all methods, development of optimum strengthdepends on proper preparation of face skins and controlledapplication of adhesive to form optimum fillets betweenmated ends or faces of the core structure. Such bondingoptimization achieves even transmission of loads from faceskins to core without bond rupture.Other forms of sandwich structure which offerexcellent high temperature strength performance arecomposed of all steel honeycomb and face skin. These aremost often resistance welded or of brazed construction.3ORPORATIOTYPICAL SANDWICH PANEL APPLICATIONSAIRCRAFT INDUSTRYFloor PanelsInterior WallsFood Handling Galley AssembliesWing Control SurfacesPassenger Storage RacksThrust Deflector AssembliesAEROSPACE INDUSTRYCapsule PanelsAblative Shields for Nose ConesInstrumentation Enclosures & ShelvesBulkhead PanelsSpace SatellitesELECTRONICS INDUSTRYElectronic Radome ConstructionLarge Antenna or Disk ReflectorsMilitary Electronic Instrumentation SheltersShipboard Electronic Deck SheltersTRANSPORTATION INDUSTRYCargo PalletsShipping ContainersRefrigeration PanelsRapid Transit Floor PanelsSpecial Automobile BodiesCONSTRUCTION INDUSTRYArchitectural Curtain WallsPartitions & Divider PanelsExpandable Hospital SheltersN
SECTION — IISECTION II — DESIGN CRITERIATRANSMITTING LOADSOf prime importance to successful utilization of asandwich structure is the method for transmitting loads intoand out of it. By its very nature, sandwich cannot carryconcentrated unit loading. Moreover, modern designerscannot resort to the crude and heavy methods of attachmentthat typified early attempts to fasten sandwich.Many of these earlier methods tended to nullify theadvantages of high strength-to-weight ratios because theyused solid sections of fillers or wooden blocks bonded inplace within the structure adding undue weight. These wereinserted by removing sufficient core volume to developrequired strength (See Figure 2).Fortunately for today’s designers, sophisticated meansof sandwich attachment have been developed by Shur-LokCorporation. The balance of this section explores the designcriteria for these insert fasteners.There are two primary load forms to be considered:shear and tension (See Figure 3). In many instancesdesigners encounter combinations of these loads in multipledirections. A study of sandwich will reveal that all primaryloading must be carried by the face skins. The cores acts asa stabilizer. Load application must therefore be spread overthe greatest possible area since the face skins are relativelythin. Proper selection of the correct fastener, used insufficient numbers, can achieve the necessary degree ofload distribution.Aside from the primary loads, there is a third, thoughless critical load. This is torque, and is usually significantonly if the insert is a threaded variety (See Figure 3). Thetorque generally results from assembly methods rather thanservice loading.Figure 3 — Typical toad FormsFigure 2 —- Solid Section Fillers4
SHUR LOKCBasically there are two types of fastener inserts forhoneycomb application: the molded-in type and the mechanical type (See Figure 4). The molded-in type shouldalways be used if possible because it offers several distinctadvantages. Among these is the ability to bond the insert,core and face skins into one rigid unit with the selectedpotting medium. Another advantage is that molded-ininserts are not particularly sensitive to manufacturingvariations within the sandwich structure. Furthermore,bonded parts necessitate a relatively short learning curvefor inexperienced installers.ORP5T1. Overall thickness of panel?2. Face skin thickness? Rigidized or plain?5. Flat, curved or tapered surface?6. Fastener molding compound?Figure 5 — Sandwich Panel ConsiderationsFigure 4 — Fastener Inserts for Honeycomb ApplicationsASandwich (See Figure 5).4. Material of core and face skins?The first logical step in the selection of a fastener is todetermine exactly what is expected of it in the specificRIONapplication under study. Typically the designer must knowthe structural arrangements of the joint involved as well asthe loads expected. The sandwich construction mustsimilarly be defined. The following two lists typify designparameters which must be considered.3. Type of core?CONSIDER THE DESIGN PARAMETERSO
SECTION — IIFastener (See Figure 6).1. Size (diameter) of through-mounting member? Boltor rivet?2. Is fastener to be through or blind type?3. Must installation be flush with surface of face skin?4. Is a facing type or standoff head required on eitherend? What diameter? How thick?5. What are torque requirements of threaded type? Isself-locking feature required?6. What material is required for fastener?7. Operating temperature of installation?8. Design load requirements for each fastener?9. Type of fastener preferred: molded-in or mechanical?10. Material compatibility of mating fastener?Naturally some of these questions cannot be readilyanswered during the first approach to design, but eventuallyall must be acknowledged before achieving a final fastenerdesign. Typically, as a result of the indeterminate characterof some applications, the magnitude and direction ofloading are unknown. Specific application testing of thefastener-installed within the sandwich, as opposed to testson the fastener alone-are therefore often required to provethe design.Since the facilities required for such combined testingare of a specialized nature, test and sample requirementshave become the responsibility of the fastenermanufacturer. He has, of necessity, developed the manyspecialized test techniques peculiar to sandwich structureand associated fasteners, Through natural evolution, themanufacturer has also developed a panoramic image not ofjust a hardware seller, but of a complete service, runningfull circle from design recommendations, hardwaredevelopment, test, installation recommendations, and thefurnishing of test samples for full prototype. These are theservices Shur-Lok Corporation offers to its customers.Figure 6 — Fastener Considerations6
SHUR LOKCA WORD ABOUT STANDARDIZATIONAside from the foregoing requirements, the duty ofmaking standardization recommendations has also fallen tothe fastener manufacturer.The best effort for standardization lies in the molded-inblind insert, because little is gained by increasing theinsert’s length once an optimum ratio of threads-to-bolt sizehas been established. Thus, while accepted design calls fora minimum of 1.5 diameters of thread engagement, 0.75diameters is sufficient to develop full bolt and sandwichstrength. The additional provision of 0.75 diameters isadequate for bolt overtravel resulting from tolerancebuildup. A nominal insert length could be used for mostsandwich applications. Obviously, ultra-thin sandwichpanels must be treated differently when attemptingsandwich insert length standardization.LOAD ANALYSISSandwich structures consisting of light gage facematerials and low density cores cannot be expected to carryany greater load than can be developed between the fastenerand the face skins. As mentioned earlier, all loads enteringthe sandwich panels are carried first through these skins.The core member acts to stabilize and transmit transversestress across the panel.The chief design consideration, then, is to keep unitloading compatible with the load capabilities of andthrough the thin face skins. This generally meansmaintaining proper load distribution and a relatively lowload per fastener by using an adequate number of the propertype and size fasteners.Regardless of sandwich construction, it is necessary tomake an analysis of total load vs. fastener size and quantity.The lighter the sandwich structure, the greater care requiredin selecting the proper fastener.TENSION LOADINGAn element analysis across any given section ofhoneycomb in any direction will indicate a structure that is7ORPORATIONvery similar to the “Wagner Beam.” The face skinsrepresent the cap strips. The vertical surfaces of cell wallsform individual shear panels, with the junctures of the cellwall acting as vertical boundary stiffeners of each smallshear panel.In tension loading of a fastener, the bonding of core toface skin plays a major role. The whole area about thefastener acts as an unsupported diaphragm, with loadcentered at the fastener. Design should strive to minimizethe unsupported diaphragm area and to obtain as muchsupport from the core material as possible. With molded-ininserts this support objective is dependent on the type ofpotting material. Its ability to fill the core voids reduces theloading per unit area and dependent upon adhesive strength,provides the ultimate in load transfer between skins, coreand insert. This support aspect is exhibited by the SL600Series’ ability to provide a completely void-free fill.With mechanical inserts, strength is derived from athrough part which can be secured to both face skins as inthe Shur-Lok SL500 Series. This method tends to reducedependency on the bond between core material and faceskin, making the unsupported diaphragm area less critical.SHEAR LOADINGDesign for shear loading must take note of face skinthickness and bearing area. The insert must remain stableand in position in order to develop full bearing load in theface skin. In common single-shear applications, the loaddevelops a relatively high upsetting moment, tending tocause the insert to turn over and lose continuity with theface skin. In the case of molded-in blind type fasteners, acomplete distribution of the potting medium around theinsert will achieve good stability. In cases of severely highunit loading, it may be necessary to undercut surroundingcells in order to provide a sufficiently large bearing area forstability. The core material plays only a secondary role insingle-shear loading; when the continuity between face skinand insert is lost, failure is quite rapid.
SECTION — IllSECTION III — APPLICATION METHODSMOLDED-IN INSERTSWith molded-in inserts, the key to proper design is theselection of a head diameter which provides sufficientbearing area in the face skin for the size of the bolt or screwto be used. The SL600 Series Shur-Tab system of fasteningis available in both blind and through types.For blind types, minimum insert length should provide1½ diameters of thread engagement. It is not generallynecessary to use a different insert length for eachapplication, but certain special considerations may arisewhich will demand a longer length for thicker panels.In these instances, however, the insert should not beallowed to touch the inner surface of the bottom skin. Aminimum of 0.040 inches clearance is recommended toallow the epoxy to flow under and around the insert. Thisassures a bond between the inside surface of the bottomskin and the fastener (See Figure 7).For through types the insert length must be precise toassure flush installation across the overall thickness of thesandwich. To help position the insert accordingly, the ShurTab system provides a special adhesive-backed tab. Epoxyis injected through one of the potting holes with a Semcosealant gun, or equivalent, which permits venting throughthe other hole thus insuring a completely uniform fill (SeeFigure 8).INSTALLATION HOLE PREPARATIONWhen drilling holes in honeycomb panel for blindinserts, it is only necessary to drill deep enough to providea clear hole having a depth of 0.020 or 0.030 inches beyondthe length of the insert. When drilling holes in panel with ahomogeneous core such as foam material, it isrecommended to drill to the inside surface of the bottomskin for maximum performance. It is not necessary to cleanup the inner surface when the core is honeycomb since anyroughness or remaining core will actually add materially tothe bond efficiency by providing additional adhesion area.The through type requires a single diameter hole throughboth face skins. The core may be undercut to provideadditional bearing surface or footprint area (See Figure 9).Incidental to the drilling of installation holes in honeycomb is a certain amount of cell opening. These opened cellsbecome filled with epoxy which provides a bond betweenface skins, cell walls and the insert. Cell size and the numberof cells opened during drilling will thus determine theamount of epoxy requires for a given installation.Figure 7 —Figure 8 —Figure 9 —Dimension ConsiderationsShur-Tab Potting OperationTypical Core Undercut for Molded-In Insert8
SHUR LOKCORPORATIMECHANICAL INSERTSWhen loading requirements warrant, a simplemechanical spacer such as the Shur-Lok SM or SN types isrecommended (See Figure 10). These spacers require only athru hole for installation and when flush mounting isrequired the “D” type head style provides the advantage ofautomatic dimpling of the face skins during installation.Mechanical inserts, such as the SL500 Series, attach toboth face skins (See Figure 11). Therefore, two sizes ofdrills or a step drill must be used to provide the installationhole (See Figure 12).There are two basic head forms on the SL500 typemechanical inserts-the dimpled or flush type, and the flathead or standoff type. Flat or standoff types require controlonly of hole size and overall length. The face skin gage,type of material and effects of dimpling must be consideredwhen using the flush type.When SL500 flush type inserts are used, the face skinsin most cases are depressed by the installation of thefastener to provide a flush installation. Most primefabricators of missile or airframe assemblies haveestablished rules controlling the method of dimpling.Some companies require predimpling of the skins forall materials. Shur-Lok Corporation recommends thatpredimpling be used on skins in excess of 0.020 inches. Forskins thicker than 0.060 inches, we suggest countersinking.Certain forms of sandwich facing will require specialconsideration. For example, most fiberglass skins cannot bedimpled but must be sufficiently thick to be countersunkwhen flush heads are required. Hot predimpling is usuallyrequired for 7075 aluminum alloy and like materials.Figure 10 — Simple Mechanical InsertFigure 11 — Shur-Torq Self-Retaining Mechanical InsertEDGE DISTANCEInsert users frequently inquire about minimum requirededge distance for sandwich fastener installation. Bestpractice is to maintain a minimum of two diameters fromthe edge based on insert head diameter. In some cases acloser edge distance may be required. The exact allowablesshould be determined by testing.9Figure 12 — Step Drill Provides Two Hole SizesON
SECTION — IVSECTION IV — MATERIALSSELECTION OF POTTlNG COMPOUNDSSelection of potting compounds can be a puzzlingproblem. There are many different brands, all claimingdesirable features. Densities range from about 40-90pounds per cubic foot. Density reduction in any compoundis achieved through the addition of fillers. Inherent withthis addition is some reduction in strength. Also, fillers leadto some stiffening which reduces workability of thecompounds.On the production line, the workability of all suchcompounds is important. Since most epoxies have potential“pot life” ranging from about 15 minutes to two hours, it isimportant to production line function that the compound iscompatible with a sealant gun and the SL600 Shur-TabSystem.Proper mechanization, using the SL600 System, willhelp lower installation time per fastener, with resultant costsavings. In this respect, filler use will depend on an analysisof weight requirements vs. economics of the overallapplication. As more filler is added to reduce density, themore difficult it becomes to mechanize installation. Theactual volume of epoxy utilized per insert varies withsandwich thickness, core density and insert size. The epoxyweight for a 3/16 inch diameter insert in a ½ to ¾ inchsandwich will range from 5 to 20 grams.Epoxies for edge sealing must handle easily whenapplied with hand tools. They must be sufficientlythixotropic in character to stay in place on vertical surfaces,and spread easily without excessive pull. Other pottingcompound considerations include adhesive strength,tendency to outgas and shrinkage during cure.TAILORED COMPOUNDS AVAILABLEHaving been directly involved with these pottingcompound requirements, Shur-Lok Corporation offersepoxy compounds tailored to meet the specialized needs ofsandwich fasteners.These epoxy systems include:1. SLE3001 which is a two-part epoxy systemdesigned specifically for use with sealant gunpotting. SLE3001 flows readily and can be pottedwith pressures as low as 20 psi, or with conventionalhand syringes. It has excellent adhesive strength. Itprovides a complete fill free from voids. It alsoexhibits excellent thixotropic characteristics, yetdoes not outgas during exothermic stage. Density is75 lbs. per cubic foot.2. SLE3002, also a two-part system, which isrecommended for the open potting method. Its flowcharacteristics are such that it will flow through the10smallest openings and fill surrounding cellscompletely. SLE3002 works well in papercorehoneycomb with excellent adhesion. Density is 75lbs. per cubic foot.3. The third epoxy compound, SLE3003, which can beused for both potting and edge bonding. Beingnonsticky, it is easy to spread into position for edgebonding and will develop adequate strength withedge potting only 1/2-cell thick. Edge finishcleanup is held to a minimum. SLE3003 alsoembodies excellent thixotropic characteristics thateliminate sag on vertical surfaces. Its adhesivequality is good. It resists chipping and spalling tosuch a degree that standard wood screws can beturned into the mass without cracking the epoxy.When selecting the material, the following factors mustbe considered:1. Strength required2. Service life of fastener3. Temperature requirements4. Corrosive environments5. Thread lock requirements6. Magnetic requirements7. Weight8. costThe last factor, cost, is not generally considered anengineering problem, but certainly should be considered inthe overall design. Designers are cautioned to avoidoverdesigning when a corrosion-resistant alloy is needed.For example, A286 alloy has superior properties ofcorrosion resistance a n d s t r e n g t h u n d e r e l e v a t e dtemperatures and prolonged exposure. Yet 17-4 PH willfrequently do the same job at 20% of the cost. Use theminimum grade that will do the job.MATERIAL SELECTIONTypical materials used in the manufacture of Shur-Loksandwich fasteners are:
SHUR LOKCMETHODS OF TESTINGAs mentioned earlier in this document, a sandwichpanel fastener cannot be tested as an individual unit, butshould be evaluated as installed in the applicable sandwichspecimen. Experience shows that failure always occurs inthe panel, never the fastener. Three basic tests arerecommended and shown in the following figures:Figure 13 Shear testFigure 14 Flatwise Tension TestFigure 15 Torque-Out TestIt is important that test procedures be standardized inorder to obtain effective design evaluation. Standard testprocedures specify the edge distance and location of thefastener within each specimen which will give the ultimatePORATIONIn addition to the three basic tests mentioned above,additional special test may be required to completelyevaluate the final fastener and panel configuration. Thesemay include fatigue, vibration and shock tests.Figure 15 — Torque-Out Test11Rload-carrying capability of a particular fastener in aspecific panel. Additional tests may be required which willinclude the true design parameters in a particularapplication to determine actual design loads. These couldbe in the nature of closer edge distances, combination pullsof two or more fasteners, or pulling straps which representthe actual attaching structure. The thickness of the pullingstraps, in the case of single shear tests, has a direct effect onthe stability of the fastener installation. The span orunsupported diaphragm area within the test ring in a tensiletest does not in some cases represent the true loadingconditions of the specific application.Figure 14 — Flatwise Tension TestFigure 13 — Shear TestO
SECTION — VRECOMMENDED TEST PROCEDURE1.0 SCOPE1.1 PURPOSEThe purpose of this document is to establish standardized procedures for the testingand qualification of sandwich fasteners. Unless otherwise specified, all tests arestatic tests to be conducted at room temperature.1.2 CLASSIFICATION OF TESTSThe test procedures outlined herein pertain to three specific phases of sandwichfastener testing and apply to the installation of th
dependent on the integrity of its fasteners. Shur-Lok Corporation, a pioneer and current frontrunner in the design and manufacture of specialty fasteners for industry, dedicates this document to a thorough comprehension of the selection of fasteners
Shur-Lok also has an extensive engineering facility to assist in the development and testing of fasteners for special applications. Illustration 5 All potted style fasteners are supplied with a Shur-Tab which greatly simplifies the installation pro-cedure. Please refer to the Fasteners for Sandwich Structure catalog for information on tab .
SHUR-CO of SOUTH DAKOTA 2309 Shur-Lok St., Yankton 800.474.8756 . NOTE: All prices in this catalog are subject to change without notice. All compo-nents other than standard may require a non-refundable engineering fee of 75 and manufacturing fee of 25. Call for details.
3 Sta-Lok Fluid Fittings 2 Sta-Lok Fluid Fittings FEATURES AND BENEFITS STA-LOK FLUID FITTING versus MS HEX NUT FITTING Sta-Lok Fluid Fittings offer tube end configurations in Beam Seal, Flared and Flareless in both inch and metric. Sta-Lok Fluid Fittings are designed to fit
fasteners for sandwich structure catalog shur-lok. 6288. inserts for metallic face skin panel sl101 insert, grommet type, thru-rivet. inserts for metallic face skin panel sl101 insert, grommet type, thru-rivet. inserts for metallic face skin panel sl101 insert, gromm
Ion Collector Kits for Versa-Spray and Versa-Spray II Automatic Guns Description This instruction sheet covers the ion collector kits for Versa-Spray and Versa-Spray II automatic guns. One kit is for guns with Shur-Lok mounts; the other is for guns with in-line ball mounts. 189491 Kit, Shur-Lok
The M-LOK system will have priority for all new accessories from Magpul, although some new items may be offered for the MOE system as well. 07. THE M-LOK SYSTEM FAQs Q: Is the M-LOK design free for any manufacturer to use? A: Yes, there is no fee to use the M-LOK design, however we do ask that manufacturers
LET-LOK 316 AV2(2) LET-LOK 316 1/2 BU2 Fig. 3 Back side Fig. 3 Fig. 4 Front side LET-LOK 316 AV2 Nut: (See Fig. 3 & 4): Shoulder marked LET-LOK 316 1/2(1) BU2(2) (1) Tube O.D. (2) Material Batch LET-LOK INCH FITTINGS: TUBE SELECTION Four variables must be considered when ordering tube for use with L
Advanced Management Accounting CIMA (P2) The best things in life are free To benefit from these notes you must watch the free lectures on the OpenTuition website in which we explain and expand on the topics covered. In addition question practice is vital!! You must obtain a current edition of a Revision / Exam Kit - the CIMA approved publisher is Kaplan. It contains a great number of exam .
