• Composites Research
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• v.36 no.6
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• pp.383-387
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• 2023

Carbon fiber-reinforced composites have excellent mechanical properties. However, the fracture toughness is a disadvantage due to brittle failure mode. The fracture toughness can be enhanced using hybridization with large-elongation fibers. In this study, polyamide (aramid) fibers are hybridized with carbon fiber with various stacking sequences. As a result, the Izod impact strength was enhanced by 63% with 25% aramid fiber hybridization. It is also shown that there is an optimal point in laminated composite hybridization, [CF/CAF₂/CF]_s stacking sequence.

• Structural Engineering and Mechanics
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• v.67 no.6
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• pp.617-628
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• 2018

This paper deals with the maximization of the critical buckling load of simply supported antisymmetric angle-ply plates resting on Pasternak foundation subjected to compressive loads using teaching learning based optimization method (TLBO). The first order shear deformation theory is used to obtain governing equations of the laminated plate. In the present optimization problem, the objective function is to maximize the buckling load factor and the design variables are the fibre orientation angles in the layers. Computer programming is developed in the MATLAB environment to estimate optimum stacking sequences of laminated plates. A comparison also has been performed between the TLBO, genetic algorithm (GA) and differential evolution algorithm (DE). Some examples are solved to show the applicability and usefulness of the TLBO for maximizing the buckling load of the plate via finding optimum stacking sequences of the plate. Additionally, the influences of different number of layers, plate aspect ratios, foundation parameters and load ratios on the optimal solutions are investigated.

• Steel and Composite Structures
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• v.31 no.4
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• pp.387-396
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• 2019

This paper deals with the effect of ply orientation and control gain on tip transverse displacement of functionally graded beam layer for both active constrained layer damping (ACLD) and passive constrained layer damping (PCLD) system. The functionally graded beam is taken as host beam with a bonded viscoelastic layer in ACLD beam system. Piezoelectric fiber reinforced composite (PFRC) laminate is a constraining layer which acts as actuator through the velocity feedback control system. A finite element model has been developed to study actuation of the smart beam system. Fractional order derivative constitutive model is used for the viscoelastic constitutive equation. The control voltage required for ACLD treatment for various symmetric ply stacking sequences is highest in case of longitudinal orientation of fibers of PFRC laminate over other ply stacking sequences. Performance of symmetric and anti-symmetric ply laminates on damping characteristics has been investigated for smart beam system using time and frequency response plots. Symmetric and anti-symmetric ply laminates significantly reduce the amplitude of the vibration over the longitudinal orientation of fibers of PFRC laminate. The analysis reveals that the PFRC laminate can be used effectively for developing very light weight smart structures.

• Structural Engineering and Mechanics
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• v.91 no.2
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• pp.135-147
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• 2024

The objective of this study is to analyze, using the finite element method, the durability of damaged and repaired structures under the effect of mechanical loading coupled with environmental conditions (water absorption and/or temperature). The study is based on the hybrid patch repair technique, considering several parameters based on the J integral to observe the behavior of the adhesive in transferring load from a damaged plate to the repair patch. The results clearly show that water absorption and increased temperature cause degradation of the mechanical properties of the adhesive, leading to an increase in its plasticization, which is beneficial for the assembly's strength. However, the degradation of the adhesive's properties due to aging in the repair results in poor load transfer from the damaged area to the patch. The findings of this study allowed the authors to conclude that the [0°]8 sequence consistently offers the best performance, with the lowest J integral values and superior crack resistance. The lowest the J integral for the [0°]8 stacking sequence is typically 3-7% lower than that of the [0/-45/45/90]S and [0/-45/90/45]S sequences at elevated temperatures. At 60℃, the J integral increases by approximately 3-6% compared to 40℃ and 20, depending on the aging duration and stacking sequences.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.164-171
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• 2005

This study aims to examine an effect of stacking sequence and curvature on the penetration characteristic of a composite laminated shell. For the purpose, we manufactured specimens with different stacking sequences and curvatures, and conducted a penetration test using an air-gun. To examine an influence according to stacking sequence, as flat plate and curvature specimen had more plies, their critical penetration energy was higher, Critical penetration energies of specimen A and C with less interfaces somewhat higher than those of B and D with more interfaces. The reason that with less interfaces, critical penetration energy was higher is pre-impact bending stiffness of composite laminated shell with less interfaces was lower than that of laminated shell with more interfaces, but bending stiffness after impact was higher. And it is because interface, the weakest part of the composite laminated shell, was influenced by transverse impact. As curvature increases, critical penetration energy increases linearly. It is because as curvature increases, resistance to in-plane deformation as well as bending deformation increases, which need higher critical penetration energy. Patterns of cracks caused by penetration of composite laminated shells include interlaminar crack, intralaminar crack, and laminar fracture. A 0$^{\circ}$ply laminar had a matrix crack, a 90$^{\circ}$ply laminar had intralaminar crack and laminar fracture, and interface between 0$^{\circ}$and 90$^{\circ}$laminar had a interlaminar crack. We examined crack length and delamination area through a penetration test. For the specimen A and C with 2 interface, the longest circumferential direction crack length and largest delamination area were observed on the first interface from the impact point. For the specimen B and D with 4 interface, the longest crack length and largest delamination area were observed on the third interface from the impact point.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.1-6
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• 2016

The Internet of Things (IoT) is a new technology paradigm demanding one packaged system of various semiconductor and MEMS devices. Therefore, the development of electronic packaging technology with very high connectivity is essential for successful IoT applications. This paper discusses both fan-out wafer level packaging (FOWLP) and 3D stacking technologies to achieve the integrattion of heterogeneous devices for IoT. FOWLP has great advantages of high I/O density, high integration, and design flexibility, but ultra-fine pitch redistribution layer (RDL) and molding processes still remain as main challenges to resolve. 3D stacking is an emerging technology solving conventional packaging limits such as size, performance, cost, and scalability. Among various 3D stacking sequences wafer level via after bonding method will provide the highest connectivity with low cost. In addition substrates with ultra-thin thickness, ultra-fine pitch line/space, and low cost are required to improve system performance. The key substrate technologies are embedded trace, passive, and active substrates or ultra-thin coreless substrates.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.944-951
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• 1988

Global-Local Laminate Variational Model is utilized to investigate the characteristics of interlaminar stresses in thick composite laminates under uniform axial extension. Various laminates with different fiber orientation and stacking sequences are analyzed to observe the behavior of interlaminar normal stresses. From this result, the interlaminar normal stress distribution along the laminate interfaces is examined and discussed with an existing approximation model. The repeated stacking of Poisson's ratio symmetric sublaminates is found to be the best stacking method of thick composite laminates to reduce the interlaminar normal stresses for the prevention of the free-edge delamination.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.1952-1959
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• 1999

The work factor approach, so-called single specimen technique could be used to determine energy release rate from a single test record for unidirectional CLS specimen. In the present study, the work factor approach was extended to determine the mixed-mode fracture toughness of multi-directional graphite/epoxy laminated composites. Multi-directional CLS specimens were used for fracture tests. The stacking sequences used for the lap and the strap were $[90_2/0_2]_s/[0_4/90_4]_s$ and $[0/\pm45/0]_s/[0_2/\pm45_2/0_2]_2$, respectively. For both cases, the fracture toughness determined from the work factor approach was compared with that determined from the compliance method. It was found that both methods produced fracture toughness within a maximum 15% difference for each stacking sequence. The fractography analysis also showed that the fiber bridging occurred for$[0/\pm45/0]_s/[0_2/\pm45_2/0_2]_2$ case while it did not occur for $[90_2/0_2]_s/[0_4/90_4]_s$ case.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.173-177
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• 2004

In this study, the effect of laminate thickness on the compressive behaviour of composite materials was investigated through systematic experimental work using the stacking sequences, [04]ns, [45/0/-45/90]ns and [45n/0n/-45n/90n]s (n = 2 to 8). The stacking sequence effects on failure strength of multidirectional laminates were examined. For this purpose, two different scaling techniques were used; (1) ply-level technique [45n/0n/-45n/90n]s and (2) sub laminate level technique [45/0/-45/90]ns. An apparent thickness effect existed in the lay-up with blocked plies, i.e. unidirectional specimens $([0_4]ns)$ and ply-level scaled multidirectional specimens ([45n/0n/-45n/90n]s). From the investigation of the stacking sequence effect, the strength values obtained from the sub laminate level scaled specimens were slightly higher than those obtained from the ply level scaled specimens. The measured failure strengths were compared with the predicted values

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.643-652
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• 1989

The purpose of this research is to analyze the impact behavior of beam-like laminates due to the transverse impact of a steel ball according to the changes of stacking sequence and aspect ratio. For this purpose, it is carried out the dynamic finite element analyses using the modified beam theory for laminates and the first order shear deformation plate theory. The results of these analyses are compared with those of experimental impact tests. The composite materials are composed of [0.deg./45.deg./0.deg./-45.deg./0.deg.]$_{2S}$ and [90.deg./45.deg./90.deg./-45.deg./90.deg.]$_{2S}$ stacking sequences and have 4.5 t * 5(10, 20 & 30)w * 200(300)l(mm)dimensions. In all analyses, the specimens are clamped at both ends.cimens are clamped at both ends.