Abstract
Fibre metal laminates are utilized in lightweight structures, such as aircraft fuselages, as fibre metal laminates provide outstanding fatigue and damage tolerance capabilities, together with a reduced weight compared to monolithic metallic structures. One critical feature of fuselage structures is their strength reduction that owes to riveting, i.e., a state-of-the-art joining technique in aircrafts. In the present work, the blunt notch strength of fibre-laminate panels with rivet holes is investigated under service-relevant biaxial loading conditions. To this purpose, cruciform specimens with a five-hole pattern were produced. These specimens were tested under various biaxiality ratios and fibre orientations. All tests were supported by three-dimensional digital image correlation to obtain the deformation field in the gauge area. Moreover, the displacement fields obtained during deformation were used in an elasto-plastic finite element model as boundary conditions to determine the maximum strains in the vicinity of the blunt notch holes and thus extend the application of the experimental results. The asymmetric strain fields obtained by digital image correlation reveal the interaction of the fibres with the blunt notch holes. Finally, it is shown that the biaxial loading conditions do not significantly influence the blunt notch strength.
Highlights
Fibre metal laminates (FML) are made of multiple layers of metallic foils and fibre reinforced polymers
This paper presents the specimen design for the biaxial tests, gives experimental results, and features a finite element simulation for profound analysis of the experiments
De Vries [5] reported that the results between open and filled blunt notch strength is negligible for GLARE 3 and 4
Summary
Fibre metal laminates (FML) are made of multiple layers of metallic foils and fibre reinforced polymers They were introduced as high-performance materials with improved fatigue and damage tolerance properties as a competitor for metallic airplane structures [1]. Failure mode: ultimate tensile strength (no notch in laminate) in fibre direction. Drilling holes in GLARE leads to the sectioning of glass fibres, i.e., the main load carrying component of the laminate is damaged. W − D nominal where W is the width of the specimen and D is the sum of the diameter of the holes This leads to a situation where the blunt notch strength depends on the size of the specimen. The typical blunt notch stress (net stress) of Standard-GLARE3-3/2-4 is about 480 MPa in the L-direction (fibre orientation 0◦ ) [1]. This paper presents the specimen design for the biaxial tests, gives experimental results, and features a finite element simulation for profound analysis of the experiments
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