Probabilistic strength prediction for double lap joints composed of pultruded GFRP profiles part I: Experimental and numerical investigations

Experimental and numerical investigations were carried out on adhesively bonded full-scale double lap joints composed of pultruded GFRP profiles with relatively thick adhesive layers. Thick adhesive layers are often used in infrastructure applications in order to compensate for geometrical tolerances. The influence of different geometric parameters on the joint strength was investigated: the thickness of the adhesive layer (5–35 mm), the fillet radius (2–10 mm) and the overlap length (100–300 mm). It was found that the joint strength (i) decreases with the adhesive layer thickness, (ii) is almost independent of the fillet radius and (iii) increases with overlap length. Joints with a shorter overlap length failed in a brittle and sudden manner, while joints with a longer overlap showed stable crack growth during decreasing stiffness after crack initiation. It was concluded that the shape of through-thickness tensile and shear stress distributions influences joint strength and that joint strength is therefore influenced by a statistical size effect.