BS EN 302-3-2004 pdf download.Adhesives for load-bearing timber structures Test methods Part 3: Determination of the effect of acid damage to wood fibres by temperature and humidity cycling on the transverse tensile strength.
E a) (10 ± 2) °C at approximately (87,5 ± 2,5) % relative humidity;
b) (50 ± 2) C at approximately (87,5 ± 2.5) % relative humidity;
C) (50 ± 2) °C at not more than 20 % relative humidity, and an air speed of (0,75 ± 0,25) mIs during testing. J
Ii’ 5.3 Airtight glass enclosures
An airtight glass enclosure, such as a dessicator with a lid, is required, with the following dimensions:
a) 21—10 I in volume;
b) maximum heighVmaximum width ratio of between 1/1 and 1/2. J 6 Method
6.1 Selection of timber
Carry out this test using spruce (Picea abies L.) having a density of (425 ± 25) kg/rn’ measured at (12 ± 1) % moisture content as determined by oven drying.
Prepare one piece of spruce 60 mm x 60 mm in cross section and at least 800 mm In length that is free from knots, straight-grained and with growth rings not wider than 2 mm and at 30° to 60° to the surfaces of the specimen.
6.2 Preparation of the bonded assemblies
Cut the piece of wood lengthwise into 2 equal pieces of rectangular cross section and store them under controlled climatic conditions to constant mass. Constant mass is defined as the mass attained when the results of two successive weighings over an interval of 24 h differ by not more than 0.1 % of the mass of the specimen.
NOTE 1 Unless an alternative moisture content is recommended by the adhesive manufacturer, condition the timber in a
standard atmosphere ((20 ± 2) C and (65 ± 5) % relative humidity) for at least seven days prior to bonding, to achieve a
moisture content 01(12 ± 1) %.
Fi Not more than eight hours before bonding, plane each surface to be bonded, to the final thickness of at least 25 mm. (1 Remove any dust carefully. Do not touch or soil the prepared surface.
For glue mixes in which the adhesive and hardener are blended before application, the glue line thickness shall be 0,5 mm, achieved by using 0.5 mm thick spacers.
If the adhesive and hardener are applied separately, the glue line thickness shall be 0,1 mm, achieved by using 0,1 mm thick spacers.
the spacers. Maintain this pressure at (20 ± 2) °C and (65 ± 5) % relative humidity for the time recommended by the adhesive manufacturer, or 24 h, whichever is the longer.
After bonding and pressing, condition the assembly for a minimum of seven days and a maximum of 14 days at
(20 ± 2) °C and (65 ± 5) % relative humidity.
NOTE 2 A longer condihonng time may be used if recommended by the adhesive manufacturer.
Record the time elapsed between the preparation of the bonded assembly and the start of temperature cycling.
6.3 Preparation of the test pieces
Using a sharp 25 mm diameter wood dnll and a piece of wood under the assembly to prevent fraying at the edges of the hole, drill holes along the length of the assembly in the plane of the bond at distances between centres of alternately (50,0 ± 0.5) mm and (30.0 ± 0.5) mm. so that a series of bond lines (25 ± 1) mm in length is produced (see Figure 2). Take care to ensure that the holes are accurately positioned. Plane the assembly symmetrically to (50,0 ± 0,5) mm x (50,0 ± 0,5) mm and cut out the test pieces (60 ± 1) mm long as shown in Figure 2.
6.4 Number of test pieces
Test a sufficient number of test pieces to provide eight valid results for the cydic treatment and eight test pieces for the control test pieces. Results from tests for all test pieces in which a solid wood failure occurred at strength values below the requirement, or in which visual examination shows that the adhesive was not correctly applied, are invalid and shall be disregarded.
6.5 Climatic and cyclic storage conditions
Store at least eight test pieces that are not from adjacent positions in the bonded assembly in the standard atmosphere ((20 ± 2) °C and (65 ± 5) % relative humidity) until testing (control). Select at least eight test pieces for the cyclic treatment, which consists of four cycles, each of which comprises three parts:BS EN 302-3-2004 pdf download.