The PPPP-treated laminate exhibited approximately the same energy absorption trend as that of the PPPP-untreated laminate, with a 10–20% improvement. The PPPP-untreated sample exhibited approximately 50% energy absorption at low impact energies of 5 and 10 J. This demonstrates that some energy is dissipated and that not all the energy supplied to the laminate is redirected back to the impactor . The laminate exhibits a fluctuated force–displacement curve at a high impact energy level. This observation was in agreement with previous studies on the response to the impact of sisal/epoxy composites .
Figure 10.
All the samples with different stacking orders were tested for their flexural strength. Reinforcement fibres are the primary load-bearing components, accounting for the majority of the strength and stiffness of the composite. Furthermore, among the several natural fibres extracted from plant leaves, PALF has the largest portion of fibre content and the minimum microfibrillar angle, which is the primary reason for its excellent impact performance .
In addition, the PPPP-treated sample exhibited approximately 30% less displacement indention than the PPPP-untreated sample. The PPPP-treated sample exhibited a significantly higher maximum contact force than the PPPP-untreated sample, 35% more than the contact force at 2.7 kN, as shown in Figure 5. The exterior top surface of the PALF layer experiences local bending and indentation in the surrounding impact region; however, the inner layer experiences a localised buckling contact force that reaches the peak load zone. A post-analysis was performed using MATLAB R2021a to compute energy absorption. In order to determine the specific perforated energy levels, a refinement test was performed between the unperforated and perforated energy levels.
- A previous study discussed the potential benefits of natural-synthetic fibre hybridisation and its implementation .
- The primary mechanism of internal damage at the rebounding stage of failure is matrix cracking.
- However, due to the organic nature of the matrix, FRPs are impermeable to vapour, they are flammable and their application on a wet surface at low temperatures is not readily achievable.
- Moreover, as a result of material symmetry, the flexural and tensile modulus of symmetric cross-ply laminate improved by 59.5% and 3.97% compared to the unsymmetric counterpart.
- Also, analytical models are developed by classical lamination theory and shear deformation theory to study the torsional vibrations of the beams.
- Lately, the research on the performance of composite structures subjected to different loading conditions has generated much interest.
Materials and Methodology
If a natural frequency of the structure is close to an excitation frequency, then severe vibration of the structure could occur. In designing structures, it is critical to know the natural frequencies of the structure. The composite beam members have been increasingly used over the past few decades in the fields of aerospace, civil and mechanical engineering due to their excellent engineering features. The composite materials are well known by their excellent combination of high structural stiffness and low weight. Figure 6 illustrates the optical micrograph of the specimen under flexural loading. This is due to the longitudinal arrangement of the fibre, which provides high resistance towards tensile loading 31,37,38.
Table 3. Torsional natural frequencies (Hz) for different stacking sequences laminate
The same observation was reported for impact damage of hemp/carbon hybrid laminates, which was studied by Pinto. According to Sezgin and Berkalp , strong bonding at the interface and strong adhesion between the carbon ply and matrix improved the mechanical strength of the laminates. The same absorbed energy trend was reported by Giasin et al. while studying the impact properties of carbon/glass laminates . When the impact energy is delivered at a low level, the computations demonstrate that quasi-isotropic laminates absorb less energy than the cross- and angle-ply laminates. Figure 15c,d illustrate the energy profiling diagrams of the laminates at ply orientation quasi-isotropic. This could contribute to the bending stiffness of the laminates; additional elements affect the amount of energy absorbed when the ply orientation changes .
- 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.
- The laminates were evacuated from the autoclave and then demoulded before cutting them into the required dimensions.
- The interlinear interface between laminates with different ply orientations is weak .
- 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 CPPC laminate demonstrated a significantly greater impact level at 20, 25, and 27.5 J for indentation (maximum), penetration, and perforation, respectively, compared to the PCCP laminate.
At a glance: Figures
Qiao et al. presented a combined analytical and experimental approach to characterize the vibration behavior of pultruded Fiber-Reinforced Plastic (FRP) composite cantilever I-beams. Investigated the analysis of Flexural-torsional vibration of open section composite beam with including shear deformation. Several researchers have carried out studies on experimental and theoretical evaluations of flexural- torsional vibration analysis for FRP structural members. Make study intended to analyze free queenwin casino review and forced vibrations of non-uniform composite beams in the Laplace domain.
This characteristic exhibited by LM1 could be due to brittle fibre breakage and matrix cracking that are less obvious in other laminates (LM2, LM3, LM4 and LM5) with a multidirectional layup sequence. The fibre orientation in LM1 is unidirectional, while LM2 and LM3 are cross-ply laminates because the direction of the fibres is at 00 and 900. The failure modes exhibited by various stacking sequences under flexural loading were analysed by capturing the surface of damaged laminates using an optical micrograph. Therefore, the effect of stacking sequence on flexural, tensile and impact damage of composite laminate is yet to be adequately studied. The results showed that the hybrid stacking pattern improved the composite tensile, flexural and impact resistance.
The laminate of 0/90° fibers have the lowest torsional natural frequencies than the other lamination schemes and thus, because 50% of the fibers are oriented at 0° direction for 0/90° laminate, and thus appropriate for bending (Flexural Modes). To investigate the influence of laminate stacking sequence, dynamic modeling is performed to 3 set of symmetrical laminates with a total of 8 layers and dimension of 400 mm length, 40 mm width and total thickness 3.2 mm. For symmetric orthotropic laminated beam previously mentioned; the torsional stiffness of the beam can be obtained by this relation, A beam with two cross-sectional planes of symmetry may undergo flexural vibration in either of the two planes of symmetry and torsional vibration . 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.