BS EN 205:1991 download free.Test methods for wood adhesives for non-structural applications — Determination of tensile shear strength of lap joints.
Introduction
European Standards giving test methods and a common classification with respect to durability classes for wood adhesives will allow considerable improvement in consumer protection and provide greater legal security in any future product liability system with regard to properties guaranteed by the adhesive manufacturer.
NOTE See also:
ISO 62:37:1987, Adhesives — Wood-to-wood adhesive bonds — Determination of shear strength by tensile loading.
ISO 6238:1987, Adhesives — Wood-to-wood adhesive bonds — Determination of shear strength by compression loading.
1 Scope
BS EN 205 describes tests for adhesives for wood and derived timber products for the assessment of their resistance to various physical effects. It does not apply to adhesives for structural use nor to the manufacture of particle boards, fibreboards, and plywood. It does not replace specific tests or tests on finished products.
The method described in this standard is suitable for the following and other applications:
— assessing the usability and quality of adhesives for wood and derived timber products:
— classifying these adhesives into the durability classes Dl to D4 of EN 204;
— assessing effects on the bond strength resulting from the bonding conditions chosen, the various conditioning sequences and the treatment of the test pieces before and after bonding:
— assessing the bond strength of bonds with thin or thick bond line.
2 Normative references
BS EN 205 incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to BS EN 205, only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies.
EN 204, Evaluation, of non-structural adhesives for joining of wood and derived timber products. Iso 554, Standard atmospheres for conditioning a ii dior testing — Specifications.
3 Joint components
3.1 Selection of wood
Prepare two unsteamed, planed, straight.-grained beech hoards1 (fagus sylvaticci L) 130 mm wide (see Figure 1) one 5 mm thick, the other (5 + a) mm where “a” is the thickness of the bond line. For a thin bond line (a 0,1 mm) use 2 boards of 5 mm thickness. The minimum density of the wood fagus sylvatica L. shall be (700 ± 100) kg/rn3 when measured on wood having a moisture content of 12 %.
The wood shall be conditioned in accordance with
ISO 554:
(23 ± 2) °C/(50 ± 5) relative humidity or (20 ± 2) °C/(65 ± 5) relative humidity.
The length of the panels shall be a multiple of 300 mm, for example 600 mm, and the angle between the growth ring surfaces and the surfaces to be bonded shall be between 30° and 90°. Limit deviations in thickness: ± 0,1 mm.
If the behaviour of an adhesive applied in a thick bond line is to be compared with its behaviour when applied in a thin bond line care shall be taken that the beech boards for both types of bond are cut from the same piece in the direction of the grain and one directly after the other. To achieve this, cut the boards in the following order: a 5 mm strip for testing the thin bond line, followed by a 5 mm strip for testing the thick bond line, followed by a 5 mm strip for testing the thin bond line, followed by a (5 + a) mm strip for testing the thick bond line.
3.2 Bonding of the joint components The bonding conditions specified by the adhesive manufacturer shall be used.
Prepare boards for use with a thin bond line, and, if the adhesive manufacturer specifies it, also for use with thick bond lines of 0,5 mm or 1,0 mm as required.
3.2.1 Thin bond lines
Bond two 5 mm thick beech boards as shown in Figure 2, with the grains running in the same direction. Distribute the pressure uniformly over the bonding surface so that 10 mm thick bonded assemblies are formed. Comply with the processing requirements specified by the adhesive manufacturer, including whether the adhesive is applied to one or both sides, the specific quantity to be applied the open and closed assembly time and the pressing conditions. The pressure applied shall be in accordance with the adhesive manufacturer’s instructions and/or information contained in quality standards.
Immediately before bonding, prepare the wooden surfaces to be bonded by either planing (the preferred method) or with abrasive paper of grain size 150 complying with the FEPA standard. Do not touch or soil the prepared surface. Indicate on the test report if the surface has been treated in a different way.
3.2.2 Thick bond lines
Such tests are carried out in order to test the behaviour of adhesives in thick bond lines, which might be caused by poor fit or by surface irregularities arising from processing techniques.
As can be seen from Figure 1 and Figure 3, the (5 + a) mm thick board is provided with grooves of depth a = 0,5 mm or a = 1 mm and width about approximately 14 mm. Apply the adhesive to the grooved board and work it well into the grooves so that they are completely filled allowing for squeezeout. Bond (5 + a) mm thick grooved boards to 5 mm thick ungrooved boards to
obtain (10 + a) mm thick bonded assemblies for the preparation of the test pieces.
Preparation of the test pieces and testing
— species of wood with botanic name
— moisture content of wood, relative to
oven-dry mass
— characteristic data relating to the bonding
procedure (for instance information about
pressing power, pressing tern perature,
pressing time)
— time between the termination of pressing
and the cutting out of the test pieces
— special treatment of the surface of the
boards to be bonded
— indication whether test pieces with a
thin (0,1 mm) adhesive line or with a
thick (0,5 mm or 1 mm) bond line have been
used respectively
— number of test pieces
— conditioning sequences applied (serial number as given in EN 204, Table 2)
— testing speed
Test results and data about the durability class
— strength T in N/mm2, rounded to 0,1 N/mm2, i.e. minimum value, maximum value and mean value
— standard variation s in N/mm2
— coefficient of variation V in %
— appearance of the surfaces of the break
— indication of the estimated portion of wood failure or wood breakage (the indications are to be graded as follows: 0, 25, 50, 75, 100 % breakage of wood) in % (mean value of all test pieces)
— description of further peculiarities of the appearance of the break
— if necessary, deviations from this standard
— indication of durability class according to
EN 204, if required
— date of the test.