Penetration and perforation are failures at the macroscopic level when the penetrators completely enter the material at which the failure of the fibres reaches a critical point . The catastrophic penetration mode in Table 4, Table 5 and Table 6 was preceded by fibre failure. High bending stresses and locally high strains under the penetrators cause fibre failure, whereas locally high stresses and the indentation effects of shear pressures cause fibre failure on the unaffected face . Matrix cracking and delamination typically occur earlier in the fracture process than fibre failure damage . The cracking is caused by tension, compression, or shear and happens parallel to the fibres.

Figure 14.

The commercial finite element program ANSYS 10.0 is used to perform a dynamic modelling to the laminated beams by performing an eigenvalue analysis. Evangelos and Sapountzakis studied the Torsional vibrations of composite bars by (BEM) boundary element method which is developed for the nonuniform torsional vibration problem of doubly symmetric composite bars of arbitrary constant cross-section. Kameswara and Mirza studied the problem of free torsional vibration and buckling of doubly symmetric thin-walled beams of open section, subjected to an axial compressive static load and resting on continuous elastic foundation. Studied the torsional vibration of open and variable cross section bars by derive analytical method is to form the dynamic stiffness matrix of the bar, including the effect of warping. Exact torsional vibration frequencies were presented by for the case of circular cross-section shafts subjected to classical boundary conditions avoiding in this way warping effects. Several researchers have dealt with torsional vibration of beams.

The Effect of Fiber Orientation and Laminate Stacking Sequences on the Torsional Natural Frequencies...

• The laminated beam is made of many plies of orthotropic materials, and the principal material axes of a ply may be oriented at an arbitrary angle with respect to the x-axis.
• The PPPP-untreated laminate exhibited a rebound effect at 5 and 10 J impact energy levels, followed by penetration at 12.5 J with a maximum curve peak of 2.0 kN, as shown in Figure 11.
• The PPPP-treated laminate exhibited a slight increase in impact strength as the laminate withstood the rebound effect zone up to 15 J before penetration at 17.5 J with a maximum force peak at 3.1 kN.
• They developed the exact dynamic stiffness matrix by directly solving the governing differential equations of an axially loaded laminated beam.
• For the PCCP laminate, the curves exhibited a rebound pattern at low impact energies of 5, 10, and 15 J.
• Similar behaviour has been reported by Bezazi et al. during flexural testing of a hybrid kevlar/glass cross-ply laminate.
• Although this theory is useful for slender beams, it does not give accurate solutions for thick beams.

However, the effects of ply orientation and stacking sequences on the low-energy impact of PALF/carbon hybrid laminate composites are yet to be investigated. This study investigated the impact response behaviours of pineapple leaf fibre (PALF)/carbon hybrid laminate composites for different ply orientations and stacking sequences. In this study, an in-depth analysis of the low-velocity impact behavior of PALF/carbon hybrid laminate composites at various ply orientations and stacking sequences was performed. The purpose of impact testing was to determine the influence of ply orientation and stacking sequence on the behaviour of the PALF/carbon hybrid laminate composite. Maximum contact force and displacement against impact energy of the hybrid laminates at ply orientations of 0°/90°2, ±45°2s. Maximum contact force and displacement against impact energy of the hybrid laminates at ply orientations of ±45°2, 0°/90°2s.

ICSIMMA 2024 - Materials interaction on physical, chemical and mechanical science

The typical rebounding effect was defined by typical load increase and discharge decrease phases with a single-peak load that is often observed in lower impact energy scenarios . The curves generally show the energy levels at which rebounding, penetration, and perforation occur during the impact test. The collected raw data demonstrate an oscillating and noisy behaviour response to the natural modes of vibration of the impacting system; shaft, hammer, and impact sensor . As illustrated in Figure 1, the laminate was clamped between two metal features with a central circular aperture where the impact occurred. The layering sequences of the laminates are summarised and illustrated in Table 2a,b.

• According to their findings, 0/90° laminates exhibited the highest impact resistance across all the examined lay-ups, mainly due to the failure strain, which is highly influenced by the fibre orientation in the laminate.
• This behaviour has been reported in previous works on Charpy impact loading of composite 43,44,45,46,47.
• Contact force–displacement of the hybrid laminates at ply orientations of ±45°2, 0°/90°2s.
• Abramovich and Livshits studied the free vibration of non symmetric Cross-ply laminated Composite Beams based on Timoshenko type equations.
• Figure 3 shows the force–displacement curve for the hybrid laminates at a ply orientation of 0°/90°8, while Figure 4 shows the force–time curves.

Table 1. Material elastic properties

The primary mechanism of internal damage at the rebounding stage of failure is matrix cracking. Upon impact, local separation from one another causes frequent damage to such systems 59,67. Therefore, delamination occurred at the interfaces of the varyingly oriented PALF and carbon layers. When the critical load is reached, the hemp layers’ presence changes the material’s response, resulting in larger damage growth at both the carbon and hemp interfaces based on c-scan images. CPPC demonstrated less distortion because of the presence of carbon in the exterior layer. For the PCCP laminate, indentation (maximum) occurred at 15 J, followed by penetration at 20 J, before perforation at 22.5 J. Energy profiling diagram of the hybrid laminates at ply orientations of (a) 0°/90°8, (b) ±45°8, (c) ±45°2, 0°/90°2 s, and (d) 0°/90°2, ±45°2s. Figure 15 illustrates the energy profiling diagram of the PALF/carbon hybrid laminate composite. Contact force–time of the hybrid queenwin casino review laminates at ply orientations of 0°/90°2, ±45°2s. The PPPP-untreated exhibited a unique fracture pattern with multidirectional cranking propagation. In his study, based on c-scan images for front and back sides, the delamination starts around the laminate’s central plane and spreads beneath it, giving the impression that the virtually rectangular zone is a little thinner. The finding was agreed upon by Romasko in his study on composite oriented at 0°/90° . A modal analysis will be carried out using ANSYS 10.0 finite element software to study the frequencies of free torsional vibrations of the mentioned composite laminated beam. In the present study, the torsional vibration behaviors of symmetrical laminated composite beams are studied. Yõldõrõm and Kõral studied the out-of-plane free vibration problem of symmetric cross-ply laminated beams using the transfer matrix method. With these requirements, this work considers the free torsional vibrations for laminated composite beams of doubly symmetrical cross sections. Finding free torsional vibrations characteristics of laminated composite beams is one of the bases for designing and modeling of industrial products. The bending mismatch coefficient between two adjacent laminates, different fibre orientations, and stacking sequences between the layers causes delamination; the delamination area increases as the mismatch coefficient increases .

1. Impact Behavior

Thus, in this study, a pre-impregnated carbon/epoxy tape was utilised to produce the laminate composite. Grigoriou and Mouritz showed the influence of stacking patterns on the fire resistance of CFRP laminates. It was revealed that the stacking pattern affects the damping and ageing time of the composites. Mlyniec, Korta, Kudelski and Uhl studied the influence of thickness, stacking sequence and thermal ageing on the behaviour of CFRP laminates.