Adhesive peel strength

[garyjh]

In the orthotropic material definition for an adhesive material the peel strength/stress is requested to be in MPa or psi i.e.  strength or stress. This is normal for most strengths. However, the aerospace industry norm for defining peel strength is by the climbing drum peel test (ASTM D 1781, ASTM D 1876 & BS EN 2243 Pt2). The units for this are load per test specimen width (Nm/m for the ASTMs and N/cm for the BS EN test method). Can Hypersizer allow input in the test specification outputted results? IT should be noted that supplier data sheets generally always supply the data for adhesives in the test method dimensions. Therefore the user does not know the strength.

[Phil]

The peel stress allowable is the only measure of peel strength that HyperSizer currently knows how to handle.  It is used to compare the peel stress from a particular stress analysis (for example, a bonded doubler analysis causes a peel stress at the reentrant corner of the bonded stiffener).  Therefore, the margin of safety compares the peel stress to the peel stress allowable.  I'm not sure how else to calculate the margin of safety.  It seems like there should be a way to convert this test specimin load from force to a stress, is that not the case?

[garyjh]

After speaking to our materials test engineers and the technical customer support engineer at Henkel (who produce a range of adhesives used in the aerospace industry) there is no known method to them of converting a peel strength which is peel on a line i.e. 1D to peel over an area i.e. 2D

Can you please offer me some advice on how you would obtain a peel strength over an area? The only way I can think of doing it is to make an assumption of the peel zone. This means it is not over a line but has an assumed length. This may lead to inaccuracies and large variation.

AID160-180 claims that the Fpeel (bondline peel strength), which I assume is the allowable which is inputted in the material database in MPa or psi,  can be obtained from a tensile shear specimen. How? The tensile shear test methods, like ASTM D 1002, 2919, 3163 & 3165, only generate shear strength. Even though I do appreciate that the tensile lap shear test specimen does generate both shear and peel stresses at failure, it is only the shear strength that can be readily measured, even if it is not the most accurate when using thin adherends. For lap shear tests with thick stiff adherends the peel is reduced and the shear strength more accurate.

This is a problem which does not allow us to fully utilise the bonded joint analysis.

[garyjh]

Can any Hypersizer forum member help with this? Any advice or assistance would be gratefully received. Find below addresses to a Henkel Hysol product used in aerospace applications and Hexcel Redux adhesives. Select the technical data sheet. All peel data is in N/mm or in-lb/in. Thanks.

EA 9396

http://www.henkelna.com/cps/rde/xchg/SID-0AC8330A-564CA868/henkel_us/hs.xsl/full-product-list-7932.htm?iname=Hysol+EA+9396&countryCode=us&BU=industrial&parentredDotUID=productfinder&redDotUID=0000000ISE

Hexcel Redux products

http://www.hexcel.com/Products/Downloads/Adhesives%20Data%20Sheets/