Investigation on in-plane and out-of-plane constraint effects for plates with I-II mixed mode cracks under biaxial compressive loading

Aluminium plates containing a single hole or multiple holes in a row are recently becoming very popular among architects and consultant engineers in many constructional applications, due to their reduced weight, as well as facilitating ventilation and light penetration of the buildings. However, there are still uncertainties concerning their structural behaviour, preventing them from wider utilization. In the present paper, local buckling phenomenon of perforated aluminium plates has been studied using the finite element method. For the purposes of the research work, plates with simply supported edges in the out-of-plane direction and subjected to uniaxial compression are examined. In view of perforations, circular cut-outs and the total cut-out size has been varied between 5 and 40% of the total plate area. Moreover, different perforation patterns have been investigated, from a single, central cut-out to a more refined pattern consisting of up to 25 holes equally distributed over the plate. Regarding the material characteristics, several aluminium alloys are considered and compared to steel grade A36 on plates of different slenderness. For each case the critical (Euler) buckling load and the ultimate resistance has been determined.A study into the boundary conditions of the plate showed that the restrictions at the edges parallel to the load direction have a large influence on the critical buckling load. Restraining the top or bottom edge does not significantly influence the resistance of the plate.The results showed that the ultimate resistance of aluminium plates containing multiple holes occurs at considerably larger out-of-plane displacement as that of full plates. For very large total cut-out, a plate containing a central hole has a larger resistance than a plate with equal cut-out percentage but with multiple holes. The strength and deformation in the post-critical regime, i.e. the difference between the critical buckling load and the ultimate resistance, differs significantly for different number of holes and cut-out percentage.

Download Full-text

Modelling Tow Compression in Textile Preforms During Composites Processing

Aerospace ◽

10.1115/imece2004-61470 ◽

2004 ◽

Author(s):

P. Potluri ◽

V. S. Thammandra ◽

R. B. Ramgulam

Keyword(s):

Deformation Behaviour ◽

Compressive Loading ◽

Final Part ◽

Initial Part ◽

Transverse Compression ◽

Fiber Assembly ◽

Compression Model ◽

Out Of Plane ◽

Composites Processing ◽

Transfer Moulding

Fiber assemblies, in the form of woven, braided, nonwoven or knitted structures, are used as reinforcements in composites. These textile structures are subjected to in-plane membrane stresses such as tensile and shear, and out-of-plane stresses such as bending and transverse compression. Amongst various modes of deformation, transverse compaction behaviour is the least understood mode; however this mode is very important for composites processing using vacuum forming, resin transfer moulding, thermoforming and hot compaction methods. The present paper reports a computational approach to predicting the load-deformation behaviour of textile structures under compressive loading. During the compression of a random fiber assembly, fibers are subjected to kinematic displacements, bending and finally transverse compression of individual fibres. In the case of interlaced architectures, such as woven and braided structures, it is convenient to deal with deformations at meso-scale involving yarns or tows, and deal with inter-fiber friction and fibre compression at yarn/tow level. It can be seen from the load deformation graphs that the initial part is dominated by bending energy and the final part by compression energy. A combined yarn bending and compression model was in good agreement with the experimental curve during the entire load-deformation cycle. On the other hand, an elastica-based bending model predicts well during the initial part while tow compression model predicts well during the final part. Inter-fiber friction was initially ignored — this is being introduced in the refined model for both the dry and wet states.

Download Full-text

Can a three-dimensional composite really provide better mechanical performance compared to two-dimensional composite under compressive loading?

Journal of Reinforced Plastics and Composites ◽

10.1177/0731684418802028 ◽

2018 ◽

Vol 38 (2) ◽

pp. 49-61 ◽

Cited By ~ 7

Author(s):

M Tarfaoui ◽

M Nachtane

Keyword(s):

Mechanical Performance ◽

Split Hopkinson Pressure Bar ◽

Compressive Loading ◽

Three Dimensional ◽

Woven Composites ◽

Two Dimensional ◽

Hopkinson Pressure Bar ◽

Out Of Plane ◽

Split Hopkinson ◽

Pressure Bar

A series of split Hopkinson pressure bar tests on two-dimensional and three-dimensional woven composites were presented in order to obtain a reliable comparison between the two types of composites and the effect of the z-yarns along the third direction. These tests were done along different configurations: in-plane and out-of-plane compression test. For the three-dimensional woven composite, two different configurations were studied: compression responses along to the stitched direction and orthogonal to the stitched direction. It was found that three-dimensional woven composites exhibit an increase in strength for both: in-plane and out-of-plane tests.

Download Full-text

The effect of remote and internal crack stresses on mixed-mode brittle fracture propagation of open cracks under compressive loading

International Journal of Fracture ◽

10.1007/s10704-017-0231-1 ◽

2017 ◽

Vol 207 (2) ◽

pp. 229-242 ◽

Cited By ~ 2

Author(s):

Hunjoo P. Lee ◽

Jon E. Olson

Keyword(s):

Brittle Fracture ◽

Mixed Mode ◽

Compressive Loading ◽

Fracture Propagation ◽

Internal Crack

Download Full-text

Experimental and theoretical investigation of mixed mode I/III brittle fracture of U-notched polystyrene components

The Journal of Strain Analysis for Engineering Design ◽

10.1177/0309324717739725 ◽

2017 ◽

Vol 53 (1) ◽

pp. 15-25 ◽

Cited By ~ 2

Author(s):

A.R. Torabi ◽

Behnam Saboori

Keyword(s):

Brittle Fracture ◽

Mixed Mode ◽

General Purpose ◽

Shear Loading ◽

Mode I ◽

Mean Stress ◽

Plane Shear ◽

Out Of Plane ◽

Notch Tip ◽

Stress Criteria

Brittle fracture of components made of the general-purpose polystyrene and weakened by an edge U-notch under combined tension/out-of-plane shear loading conditions (mixed mode I/III) has not been studied yet experimentally or theoretically. In this research, a recently developed loading fixture is employed for experimentally investigating the fracture of U-notched general-purpose polystyrene samples with various notch tip radii of 0.5, 1, 2 and 4 mm when they are subjected to different combinations of tension/out-of-plane shear. The samples are fabricated with four different notch tip radii with the purpose of assessing the influence of this geometrical parameter. The experimental values of fracture load and out-of-plane fracture angle are theoretically predicted by the two stress-based criteria of point stress and mean stress lately extended to general loading case of mixed mode I/II/III. It is shown that both the point stress and mean stress criteria provide acceptable predictions to fracture behavior of U-notched general-purpose polystyrene specimens. The critical distances needed for the point stress and mean stress criteria are determined based on the experimental results of the U-notched samples tested under pure mode I loading. No meaningful difference is found between the fracture loads and fracture initiation angles predicted by the point stress and mean stress criteria. It is also observed that as the mode III contribution in the applied mixed mode I/III loading increases, a larger total external load is needed for the fracture of U-notched general-purpose polystyrene specimens to occur.

Download Full-text