Investigation of a secondary bonded pultrusion composite laminate containing a ply-drop, Part 1: Experimental study of a structural element specimen

This is the first of two papers which presents a novel numerical method to predict the debond failure of a secondary bonded pultrusion laminate. In this paper, experimental work will be described that will later be used in the development, calibration and validation of the numerical model, which will be discussed in the second paper. The structure investigated in this work may be represented by a bonded composite laminate with external ply-drops. The laminate is composed of unidirectional pultrusion carbon fiber reinforced polymer cured plies bonded together to produce a secondary bonded laminate. In order to investigate the different failure modes of the ply-drop structure, an element specimen denoted as a ply-drop specimen, was tested under two types of loadings: axial tension and bending. Testing procedures of this type of specimen are not well established. Thus, test protocols will be suggested. In addition, finite element analyses are carried out using established linear elastic fracture mechanics methods to investigate the conditions during debond failure and in order to assess the ability of the methods to predict the debond failure.