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A DIC-based study of flexural behaviour of roving/mat/roving pultruded composites

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Abstract This paper reports a study of the flexural behaviour and resultant failure modes in E-glass/polyester pultruded composites. The digital image correlation (DIC) method is used to estimate the effect of fibre orientation on failure behaviour in thick beams, taking into account the presence of continuous filament mat layer (CFM) in the stacking sequence. In particular, the tests were carried out for specimens with off-axis angle of 0°, 7.5°, 15°, 30°, 45° and 90°. The crack initiation and the failure mechanisms depend on the mutual interaction between the stiffness properties of different areas in the stacking sequence. An influence index (I) was introduced to evaluate the magnitude of these phenomena. For small orientation angle (i.e. less than 7.5°), the failure mechanism is not influenced by the central mat layer and the crack starts from the tension region. For angles between 15° and 45°, the influence of the central mat layer is predominant and delamination occurs at the interface between the mat layer and the adjacent one. For 90° angles, the CFM layer does not influence the typical fracture mechanism and transverse matrix cracking occurs.