Rizal Zahari

Hybrid Composite Laminates Reinforced with Kevlar/Carbon/Glass Woven Fabrics for Ballistic Impact Testing

Current study reported a facile method to investigate the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption by running the ballistic test at the high velocity ballistic impact conditions. The velocity and absorbed energy were accordingly calculated as well. The specimens were fabricated from Kevlar, carbon, and glass woven fabrics and resin and were experimentally investigated under impact conditions. All the specimens possessed equal mass, shape, and density; nevertheless, the layers were ordered in different stacking sequence. After running the ballistic test at the same conditions, the final velocities of the cylindrical AISI 4340 Steel pellet showed how much energy was absorbed by the samples. The energy absorption of each sample through the ballistic impact was calculated; accordingly, the proper ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterise the material properties for the different layers.

SECOND-ORDER SHEAR DEFORMATION THEORY TO ANALYZE STRESS DISTRIBUTION FOR SOLAR FUNCTIONALLY GRADED PLATES

Second-order shear deformation theory (SSDT) is applied to evaluate the displacement and stress fields of a solar functionally graded plate (SFGP) due to mechanical loadings. The material properties are graded by a simple power law between Full-ceramic and Full-metal at upper and lower surfaces, respectively. Naviers method is applied to find analytical results for derived equations by using energy method in case of simply supported boundary conditions. The effects of the material grading index of the plate on the stresses and displacements are investigated. It is revealed that the longitudinal stresses in the functionally graded (FG) plates lie between full-metal and full-ceramic plates. It is found that the neutral axes for SFGP move to upper surface and not at the mid-surface as predicted in the homogeneous plates. The SSDT has computed acceptable results for in-plane stresses and displacement fields when compared with the existing literatures.

Natural frequency of F.G. rectangular plate by shear deformation theory

Natural frequency of functionally graded (F.G.) rectangular plate is carried out by using second-order shear deformation theory (SSDT). The material properties of functionally graded rectangular plates, except the Poissons ratio, are assumed to vary continuously through the thickness of the plate in accordance with the exponential law distribution. The equations of motion are obtained by energy method. Numerical results for functionally graded plates are given in dimensionless graphical forms and the effects of material properties on natural frequency are determined.

Tensile strength of notched woven fabric hybrid glass, carbon/epoxy composite laminates:

This study investigates the effect of hybridization on tensile strength of woven fabric glass/epoxy composite laminates with two different notch sizes of 5 mm and 10 mm. Tensile tests are performed on notched [0°/90°]3s specimens of woven fabric C-glass/epoxy composite laminates and their hybrid reinforced with woven fabric 3K-carbon layers in order to measure tensile strength and characterize damage mechanisms. The results suggest that hybridization has a considerable effect on the improvement of the tensile strength of C-glass/epoxy composite laminates but also has reduced the rupture strain of the composites. Microscopic observation of specimens after tensile loading reveals the existence of transverse and longitudinal cracks, delamination and transverse fiber damage in hybrid composite laminates.

The Effects of Stacking Sequence Layers of Hybrid Composite Materials in Energy Absorption under the High Velocity Ballistic Impact Conditions: An Experimental Investigation

In the current study, the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption, which were fabricated from Kevlar, carbon, glass fibres, and resin have been experimentally investigated at the high velocity ballistic impact conditions. All the samples have equal mass, shape, and density, nevertheless, they have different stacking sequence layers. After running the ballistic test in the same conditions, the final velocities of the bullets showed that how much energy absorbed by the samples. The energy absorption of each sample through the ballistic impact has been calculated, accordingly, the decent ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterize the material properties.

The Behaviour of Fibre-Metal Laminates under High Velocity Impact Loading with Different Stacking Sequences of Al Alloy

The high velocity impact response of composite laminated plates has been experimentally investigated using a nitrogen gas gun. Tests were undertaken on fibre-metal laminate (FML) structures based on Kevlar-29 fiber/epoxy-Alumina resin with different stacking sequences of 6061-T6 Al plates. Impact testing was conducted using a cylindrical shape of 7.62 mm diameter steel projectile at 400m/s velocity, which was investigated to achieve complete perforation of the target. The numerical parametric study of ballistic impacts caused by similar conditions in experimental work is undertaken to predict the ballistic limit velocity, energy absorbed by the target, and comparisons between simulations by using ANSYS AUTODYN 3D v.12.1 software and experimental work to study the effects of the shape of the projectile with different (4, 8, 12, 16 and 20mm) thicknesses on the ballistic limit velocity. While only one thickness was used with 24mm of back stacking sequence, it was not penetrated. The sequence of the Al plate position (front, middle and back) inside laminate plates of the composite specimen was also studied. The Al back stacking sequence plate for the overall results obtained was the optimum structure to resist the impact loading. The simulation results obtained of the residual velocity hereby are in good agreement with the experimental results with an average error of 1.8%. The energy absorption was obtained with 7.3% and 2.7% of the back to front and back to middle of the Al stacking sequence respectively. Hence, the back Al stacking sequence is considered the optimum position for resisting the impact loading. The data showed that these novel sandwich structures exhibit excellent energy-absorbing characteristics under high-velocity impact loading conditions. Hence, it is considered suitable for aerospace applications.

Tensile strength of notched carbon/glass/epoxy hybrid composite laminates before and after fatigue loading

Hybrid laminates consisting of C-glass woven fabric/epoxy composite plies and 3k-carbon woven fabric/epoxy composite plies are studied for fatigue damage and residual strength. Tension–tension fatigue tests were conducted on notched composite laminates at two load ratios of 0.1 and 0.25. The laminates were fabricated with the hand lay-up process for a symmetrical stacking sequence [0/90]3s made of three 3k-carbon/epoxy composite plies at both top and bottom sections and six C-glass/epoxy composite plies in the middle. Fatigue damage was generated on notched specimens with 4 × 104 load cycles to damage for residual strength tests. The hybridization was found to be beneficial for relative damage sensitivity under one of four different fatigue conditions although its effect was marginal while three other conditions were not in favor. A relative damage sensitivity factor expression (or a criterion) was developed for quantitative comparisons between non-hybrid and hybrid composites and was theoretically demonstrated to be valid for any possible cases where various combinations are possible due to differences in strength reduction rate between two different composite systems. A theoretical framework with the relative damage sensitivity factor is proposed as a guide to deal with the complexity involving uncertainties and a large number of variables in the hybrid composite system. New damage mechanisms of the hybrid system due to dissimilarity between two sub-composite systems (i.e. glass/epoxy and carbon/epoxy) were hypothesized and tested to be valid with evidence based on microscopic and macroscopic examinations. The difference between static and fatigue damage is discussed.

Thermal Buckling and Post-Buckling Improvements of Laminated Composite Plates Using Finite Element Method

Thermal buckling and thermal post-buckling behaviours of laminated composite plates are improved by embedding shape memory alloy wires within laminates of composite plates. The procedure is to use the recovery stress that is induced when the reverse transformation of the shape memory alloy from martensite to austenite phases is constrained. For aerospace applications where the source of the shape memory alloy heating is the high temperature environment itself, a study is conducted to see the effect of shape memory alloy in improving the thermal buckling and post-buckling of composite plates. Due to the temperature dependent nature of the composite matrix and the shape memory alloy, the finite element formulation developed here is in the incremental form. Solving this non-linear model using the developed in-house source code, critical loads are determined and the post-buckling paths of the shape memory alloy composite plates are traced. This study shows that by embedding the shape memory alloy within composite plates, the thermal buckling and post-buckling behaviours of composite plates can be improved substantially.

The instability improvement of the symmetric angle-ply and cross-ply composite plates with shape memory alloy using finite element method

Shape memory alloy (SMA) wires were embedded within laminated composite plates to take advantage of the shape memory effect property of the SMA in improving post-buckling behavior of composite plates. A nonlinear finite element formulation was developed for this study. The plate-bending formulation used in this study was developed based on the first order shear deformation theory, where the von Karmans nonlinear moderate strain terms were added to the strain equations. The effect of the SMA was captured by adding recovery stress term in the constitutive equation of the SMA composite plates. Values of the recovery stress of the SMA were determined using Brinsons model. Using the principle of virtual work and the total Lagrangian approach, the final finite element nonlinear governing equation for the post-buckling of SMA composite plates was derived. Buckling and post-buckling analyses were then conducted on the symmetric angle-ply and cross-ply SMA composite plates. The effect of several parameters such as the activation temperature, volume fraction, and the initial strain of the SMA on the post-buckling behavior of the SMA composite plates were studied. It was found that significant improvements in the post-buckling behavior for composite plates can be attained.

Preliminary Review of Biocomposites Materials for Aircraft Radome Application

An aircraft radome usually refer to radar transparent, dome-shape structures which protects radar antennas on aircraft from aerodynamic loading, weather as well as impacts from bird strikes. Materials that are used for small aircraft radome usually have low dielectric constant and high toughness. Current composite material using high strength fibers such as glass fiber, carbon and aramid are commonly used in aerospace structures. However, the need for biodegradable materials has prompted the usage of natural fibers. Natural fibers have comparable mechanical properties such as low weight, low cost, renewable and biodegradable. In this preliminary work, comprehensive reviews of biocomposites materials are discussed in term of their properties for the purpose of evaluation for aircraft radome application. The present review will cover five local natural fibers namely bamboo, banana, kenaf, oil palm and pineapple leaf fiber.