Pin bearing test
Test Validation Programme
The proposed method uses the preferred plain pin test to determine a basic 'material' bearing strength. This method is similar to the ASTM D 5961M, which uses a torqued bolt. The torqued bolt test has several difficulties concerning the level of torque, the choice of failure criterion, the washer and thread size and condition; the effect of composite/washer friction and time-dependent changes in the torque (e.g. relaxation, swelling).
Materials investigated
- Quasi isotropic carbon fibre/epoxy, autoclave moulded (CFRP)
- Woven glass fibre/epoxy, press moulded Material
- Chopped strand-mat glass fibre/polyester (CSM) hand lay-up
- Glass fibre/polyester mixed format, pultrusion (PUL)
The RR exercise involved seven test-laboratories, representing a range of end-users. Each participant received coupon specimens machined to size and were required to machine a hole in the correct position, and then conduct the test according to the draft procedure. A pin bearing fixture was available for loan to the participants if required. The preliminary manufacture of coupon specimens was carried out by NPL. Subsequently, hole machining and specimen testing was performed by the participants. The prior round-robin results for this test were unsatisfactory, as participants had insufficient side clearance in the test jig, so that the material deformation (including Poisson's ratio effects) caused the specimen to "lock-up" as for a torqued bolt test, resulting in an inconsistent and higher peak load.
