1、 FORD LABORATORY TEST METHOD BU 121-01 Date Action Revisions 2000 12 11 Revised Rev formulas on page 5 and 6, updated N. Lindsay-Merte 1999 04 21 Printed copies are uncontrolled Page 1 of 10 Copyright 2000, Ford Global Technologies, Inc. IMPACT PEEL TEST FOR ADHESIVE BONDS Application This method is
2、 used to evaluate the relative ability of adhesive systems to dissipate energy in peel mode during an impact load. For relative comparisons, the same lot of material must be used for the substrate as the test is dependent on the stress-strain behavior of the substrate. Reference This test method was
3、 developed as an extension to the ISO 11343 method for wedge impact, “Adhesives - Determination of dynamic resistance to cleavage of high strength adhesive bonds under impact conditions-Wedge impact method.“ The specimen size and wedge shape are the same. However, the specimen configuration, the met
4、hod of constraining the specimen and test machine in this test are different. Apparatus Required Instrumented Impact Testing Machine An instrumented impact testing machine capable of applying an impact energy of at least 150 J and an impact speed of at least 3 meters/ second. Ensure that the velocit
5、y of the tup does not decrease during the impact test. The machine shall record the force data as a function of time or displacement during the impact. Universal Tensile Testing Machine An instrumented tensile testing machine with an accuracy of 0.5 % of the range used. Temperature Chamber A chamber
6、 which maintains the specimen and wedge at constant temperatures between - 40 and 100 1 C. Test Wedge The test wedge shall be fabricated from hardened steel with the dimensions shown in Figure 1. Depth of the wedge should be at least 100 mm. The wedge shall be periodically inspected for wear and sho
7、uld be kept clean. Test Hammer The hammer shall be fabricated from hardened steel and shall be a rectangle at least 25 mm by 5 mm to ensure impact over the entire top of the specimen. FORD LABORATORY TEST METHOD BU 121-01 Page 2 of 10 Copyright 2000, Ford Global Technologies, Inc. Test Coupons Test
8、coupons shall be 90.0 0.1 mm x 20.0 0.1 mm x hi where hi is the thickness of the substrate as specified by the test requester. Materials Required Glass Beads Solid glass beads to control bond-line thickness may be obtained from Mo-Sci Corp., 4000 Enterprise Dr., P.O. Box 2, Rolla, Missouri 65402-000
9、2, Tel: 573-364-2338, Fax: 573-364-9589. It is the responsibility of the requester to define the desired diameter. However, a commonly employed glass bead diameter for metal to metal bonding is 0.25 0.01 mm. Occasionally 0.75 0.01 mm diameter glass beads are used especially for bonding polymeric sub
10、strates. Substrate Type, thickness, contamination, lubrication, treatment and cleaning shall be obtained from the test requester. Adhesive Material and cure conditions shall be obtained from the requester. Tape Adhesively backed PTFE tape used to control the bonded area, may be obtained from McMaste
11、r-Carr PO Box 94930, Cleveland, Ohio 44101-4930, Phone: (330) 995-5500, Fax: (330) 995-9600. The product is “Optically Clear FEP (fluorinated ethylene polypropylene) Teflon tape“. Product #7562A11. Conditioning and Test Conditions All test values indicated herein are based on material conditioned in
12、 a controlled atmosphere of 23 +/- 2 C and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. Procedure 1. This test method requires the preparation of 5 test specimens for each condition tested. Prepare the specimens
13、 as in Figure 2. First place Teflon tape around the coupons (both the upper and lower coupons) 30.0 0.2 mm from one end. Then apply the adhesive to the top 30 mm. The bond-line thickness is maintained with glass beads. Remove adhesive squeeze out from the specimen edges with a spatula. Clamp specime
14、ns together to maintain flushness of coupon ends and sides. Cure assembled specimens per: the adhesive manufacturers recommendations, as required in a Ford engineering document, or as required by the test requester. After the adhesive is cured, remove any excess adhesive from the edges by sanding. 2
15、. Mark coupons 40.0 0.2 mm from the bonded end as a locator for consistent placement on wedge. FORD LABORATORY TEST METHOD BU 121-01 Page 3 of 10 Copyright 2000, Ford Global Technologies, Inc. 3. Place specimen on wedge, aligning mark on specimen with tip of wedge as shown in Figure 3. It is importa
16、nt to consistently align the specimens at the same place on the wedge. Do not prebend the specimens; however, allow the unbonded portion of the specimens to conform to the shape of the wedge as the specimens are placed onto the wedge. Ensure specimen is square with the impact hammer. It is critical
17、that the hammer impact the entire specimen simultaneously. 4. Impact specimens at velocity specified by test requestor. See Figure 4, for diagram of specimen during impact test. 5. Impact per Ford engineering document. After impact, measure the radius of curvature, Ri, of the coupons as specified in
18、 Appendix I. 6. Calculate the critical bending moment per unit width, Mi /b, and fracture toughness 0 as specified in Appendix II. Report 1. Adhesive identification, including: manufacturer, code number, type, date manufactured, and cure method, time, temperature and any other specific cure paramete
19、rs, e.g. power level. 2. Substrate identification, including: manufacturer, code number, thickness, stress-strain behavior, treatment, contamination and cleaning. 3. Bond-line thickness. 4. Conditioning procedure for specimens prior to testing. 5. Test conditions, including: impact velocity, sample
20、temperature and environment. 6. Failure loci: cohesive within the adhesive, interfacial between adhesive and substrate or mixed (give percentage of each). 7. One representative Force vs. Displacement curve. 8. The stress-strain curve parameters, A and n, from the power-law fit See Appendix II. 9. Th
21、e radii of curvature, Ri and the toughness 0 See Appendices I and I. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD BU 121-01 Pa
22、ge 4 of 10 Copyright 2000, Ford Global Technologies, Inc. APPENDIX I Calculation of Radius of Curvature of the Impacted Specimens Ia. Place the curved coupons on their side on an overhead projector and project the magnified curvature on a flat solid screen. Attach a page of paper to the screen so th
23、at the projected curves fit within the boundary of the page. Ib. Estimate the magnification factor of the projected images as follows: using the flat (unbonded) end of one coupon, project it across its full width, b, squarely across the page. With two short parallel lines, mark on the page the proje
24、cted width of the coupon, bp. Ic. Ignoring the initial and final 5 mm of the curved portion of the coupons trace the projected curve of the tested piece. For each coupon, it is important to note the particular side used to generate the traced curves: top = adhesive side of coupon, and bottom = clean
25、 side of coupon. Id. For each traced curve, draw and measure the lengths of the chords ABi and CDi as shown in Figure 5a. Chord CDi is constructed either by bisection of the chord ABi or by constructing the tangent line to the arc parallel to chord ABi. The radius of curvature for that arc is calcul
26、ated from the rectangular properties of chords and is given by: + +=mihiCDmmihiCDiABiR222222where m = b p /b is the magnification factor, and hi is the coupon thickness, and the index i refers to each coupon. If the traced curve was generated from the adhesive (top) side of the coupon instead of the
27、 bottom side, then the h mi2 term would be subtracted from CDi. FORD LABORATORY TEST METHOD BU 121-01 Page 5 of 10 Copyright 2000, Ford Global Technologies, Inc. APPENDIX II Calculation of Moments and Adhesive Toughness Reference For background on the theory and derivation of the equations, please s
28、ee “Determining the Toughness of Plastically-Deformed Adhesive Joints“, Thouless, M.D., Adams, J.L., Kafkalids, M.S., Ward, S.M., Dickie, R.A., and Westerbeek, G.L., Journal of Material Science, 33, 189, (1998). Substrate Stress-Strain Behavior IIa. Conduct a uniaxial tensile test of at least 3 coup
29、ons from each metallic substrate and for each thickness according to ASTM A370. IIb. Determine the best fit power-law hardening curve, = Ai ni to the stress-strain curve obtained for true strains less than 12 % as shown in Figure 6. Here the index i refers to each material, or thickness, comprising
30、the substrates. Non-linear curve fitting software, e.g. Sigmaplot, should be used to calculate A and n. NOTE: Because the range of interest includes from 0 to 12 % strain, do not use a linear form of the curve fitting equation to determine A and n. IIc. The critical bending moment per unit width, Mi
31、 /b, on each coupon is calculated from the radius of curvature and is given by: MbA hn Ri i inni inii i= +212 2( )where the index i refers to each coupon. IId. The toughness 0 is given by: 11212101)1)(2(232 +=+= iiiiniiinniiini RnnhnA where the index i = 1,2 refers to each of the two coupons, compri
32、sing each specimen, respectively. Example 1: A specimen is made from coupons of equal thickness, h1 = h2, and from the same material, A1 = A2 and n1 = n2. The toughness is: += + 1211121011)1)(2(232 nnnnnRRnnAnh where R1 and R2 are the radii of curvature of the coupons respectively. FORD LABORATORY T
33、EST METHOD BU 121-01 Page 6 of 10 Copyright 2000, Ford Global Technologies, Inc. Example 2: A specimen is made from coupons with unequal thicknesses, h1 h2 but from the same material. This does not guarantee that the power law constants will be equal, so A1 A2 and n1 n2 in general. The toughness is:
34、 +=+122212222111111211110 22221111 1)1)(2(2321)1)(2(232nnnnnnnnRnnhnARnnhnA where R1 and R2 and h1 and h2 are the radii of curvature and thicknesses, respectively, of the two coupons that comprise the specimen. Check that the applied moment on each coupon is approximately the same, i.e. check that M
35、1 = M2. That implies we should have (from IIc above): MbA hn RMbA hn Rnninnn n1 1 12112 2 2212 211 122 22 2 2 2= + = +( ) ( )NOTE: A discrepancy larger than 10% in applied moments may be an indication of poor placement of specimens on the wedge. FORD LABORATORY TEST METHOD BU 121-01 Page 7 of 10 Cop
36、yright 2000, Ford Global Technologies, Inc. Figure 1: Impact Wedge - Side View Figure 2: Specimen Design FORD LABORATORY TEST METHOD BU 121-01 Page 8 of 10 Copyright 2000, Ford Global Technologies, Inc. Figure 3: Impact Peel Set-up Configuration Figure 4: Impact Peel Configuration While Testing FORD
37、 LABORATORY TEST METHOD BU 121-01 Page 9 of 10 Copyright 2000, Ford Global Technologies, Inc. Figure 5a: Radius Determination from Rectangular Properties of Chords Figure 5b: Correct Radius for Coupon Thickness FORD LABORATORY TEST METHOD BU 121-01 Page 10 of 10 Copyright 2000, Ford Global Technologies, Inc. Figure 6: Tensile Test of Substrate with Power-Law Fit
