The ASTM D5868-01 Lap shear adhesion standard test method for fiber-reinforced plastic (FRP) bonding, developed by the American Society for Testing and Materials (ASTM) , describes a lap shear test method used to measure the bonding properties of adhesives for joining fiber-reinforced plastics to themselves and to metals. This method is applicable to both randomly oriented and fiber-oriented fiber-reinforced plastics.
-baglantisi-icin-lap-kesme-yapisma-standardi-test-yontemi.jpg "ASTM D5868-01 Lap Shear Adhesion Standard Test Method for Fiber-Reinforced Plastic (FRP) Joints")
This test method aims to complement the test method described in ASTM D1002-10 Standard test method for apparent shear strength of metal specimens joined with single-layer joint adhesive by tensile loading (metal-to-metal) and to extend its application to single-lap shear adhesive joints of fiber-reinforced plastic adhesives. This test method is useful for generating comparative apparent shear strength data for joints made from a range of fiber-reinforced plastic materials and provides a tool by which fiber-reinforced plastic surface treatments can be compared.
Adhesive terms and definitions for this test method are covered in the standard “ASTM D907-12 Standard Terminology for Adhesives”.
This test method includes a procedure for testing overlap shear bond strengths using composite materials, such as fiber-reinforced plastic, that are not recommended in ASTM D3163-01 Standard Test Method for Determining Tensile Shear Strength of Adhesively Bonded Rigid Plastic Lap-Shear Joints.
Because of the increasing use of bonded fiber-reinforced plastics due to the inherent advantages of bonded rather than mechanically fastened joints (especially the reduction of stress risers and stress cracks), there is a need for tests that can be used to compare the bonds of various fiber-reinforced plastic substrates and adhesives. This test method is designed to meet this need. Additional information on significance and use is included in “ASTM D4896-01 Standard Guide for Use of Adhesively Bonded Single Lap Joint Specimen Test Results.”
Apparent shear strength can be affected by substrate treatments such as moisture absorption and strength.
The testing machine used in these tests must have self-aligning grips that comply with the requirements of the machine defined in the “ASTM E4-20 Standard Practices for Force Verification of Testing Machines” standard and can grip the specimen securely without slipping throughout the test.
The test substrates, fiber-reinforced plastic-metal composition (heat treatment, tempering and conditioning) and roughness shall be as specified in the standard. Fiber-reinforced plastic pieces shall be cut into flat coupons with dimensions of 25,4 mm x 100 mm and a nominal thickness of 2,5 mm. In the case of fiber-reinforced plastic-metal bonding, metal with a nominal thickness of 1,5 mm shall be used. It is recommended to use a diamond-tipped water-cooled saw blade or a cutting method capable of producing sharp cutting edges.
When surface preparation is performed, the fiber-reinforced plastic surface is prepared in accordance with “ASTM D2093-03 Standard Practice for Preparation of Plastic Surfaces Prior to Adhesive Bonding” or as recommended by the adhesive manufacturer. Surface roughening, solvent cleaning, and surface primers are acceptable as long as they do not reduce the bulk properties of the FRP. Surface preparation adapted to actual production conditions is used. Metal surfaces are prepared to eliminate burrs or bevels. Clean and dry or surface treated prior to bonding using procedures prescribed by the adhesive manufacturer.
In preparing the test joints, the adhesive is applied in accordance with the adhesive supplier's recommendations or as documented in the test report. In the case of two-part adhesives, it is mixed in accordance with the supplier's recommended procedures. The adhesive is cured at room temperature or elevated temperature using the prescribed conditions determined by the adhesive supplier. The joint geometry is controlled by appropriate fixturing using glass beads or other suitable means to control the adhesive bond line thickness of 0,76 mm. The minimum number of glass beads required to maintain the bond line thickness is used in the adhesive line. Fixturing pressure is allowed. Lap shear overlap shall be 25,4 mm x 25,4 mm.
If high temperature cures are used, allow the bonded parts to cool to room temperature for at least 1 hour. If the adhesive is cured at room temperature, allow the full cure time plus 10 percent before testing.
The initial grip separation is at least 25,4 mm to 75 mm of each specimen end held in the test grips. The specimen loading rate is 13 mm)/min. A loading rate of 0,5 is a significant difference compared to other ASTM standards. In each case, at least five overlapping shear specimens are prepared and tested.
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