• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.69-73
• /
• 2001

Damage induced by low-velocity impact on the curved composite laminates was experimentally evaluated for CFRP cylindrical shells with the radius of curvatures of 50, 150, 300, and 500 mm. The result was then compared with that of flat laminates. The radius of curvatures and the effective shell stiffness appeared to considerably affect the dynamic impact response of curved shells. Under the same impact energy level, the maximum contact force increased with the decreasing radius of curvatures, with reaching 1.5 times that for plates at the radius of curvature of 50 mm. Since the maximum contact force is directly related to the impact damage, curved laminates can be more susceptible to delamination and less resistant to the low-velocity impact damage. The distribution of delamination along the thickness direction of curved laminates are also different from that of flat plates. Delamination was distributed rather even]y at each interface along the thickness direction of curved laminates. This implies that the effect of curvatures has to be considered for the design of a curved composite laminate.

• 한국안전학회지
• /
• 제17권1호
• /
• pp.1-5
• /
• 2002

An approach for the damage of delamination which is the major concern during mechanical working for composite laminate material is proposed based on linear elastic fracture mechanics. This paper presents method evaluating of damage crack length using by average thrust force with AE characteristics. Also, the relations of AE characteristics are obtained from delamination damages. We found the onset ply of the delamination and a critical energy release rate and expressed a stress intensity factor by AEcount equation.

• Steel and Composite Structures
• /
• 제17권4호
• /
• pp.387-403
• /
• 2014

This paper presents a high accuracy Finite Element approach for delamination modelling in laminated composite structures. This approach uses multi-layered shell element and cohesive zone modelling to handle the mechanical properties and damages characteristics of a laminated composite plate under low velocity impact. Both intralaminar and interlaminar failure modes, which are usually observed in laminated composite materials under impact loading, were addressed. The detail of modelling, energy absorption mechanisms, and comparison of simulation results with experimental test data were discussed in detail. The presented approach was applied for various models and simulation time was found remarkably inexpensive. In addition, the results were found to be in good agreement with the corresponding results of experimental data. Considering simulation time and results accuracy, this approach addresses an efficient technique for delamination modelling, and it could be followed by other researchers for damage analysis of laminated composite material structures subjected to dynamic impact loading.

• Steel and Composite Structures
• /
• 제23권3호
• /
• pp.263-271
• /
• 2017

A theoretical study was carried-out of mode II delamination fracture behavior of the End Loaded Split (ELS) functionally graded beam configuration with considering the material non-linearity. The mechanical response of ELS was modeled analytically by using a power-law stress-strain relation. It was assumed that the material is functionally graded transversally to the beam. The non-linear fracture was investigated by using the J-integral approach. Equations were derived for the crack arm curvature and zero axes coordinate that are needed for the J-integral solution. The analysis developed is valid for a delamination crack located arbitrary along the beam height. The J-integral solution was verified by analyzing the strain energy release rate with considering material non-linearity. The effects of material gradient, non-linear material behavior and crack location on the fracture were evaluated. The solution derived is suitable for parametric analyses of non-linear fracture. The results obtained can be used for optimization of functionally graded beams with respect to their mode II fracture performance. Also, such simplified analytical models contribute for the understanding of delamination fracture in functionally graded beams exhibiting material non-linearity.

• Advanced Composite Materials
• /
• 제16권3호
• /
• pp.223-244
• /
• 2007

This study experimentally and numerically investigated the tensile damage progress in stitched laminates. In particular, it focused on the effects of stitching on the damage progress. First, we experimentally confirmed that ply cracks and delamination appeared under load regardless of stitching. We then performed damage-extension simulation for stitched laminates using a layer-wise finite element model with stitch threads as beam elements, in which the damage (ply cracks and delamination) was represented by cohesive elements. A detailed comparison between observation and the simulated results confirmed that stitching had little effect on the onset and accumulation of ply cracks. Furthermore, we demonstrated that the stitch threads significantly suppressed the extension of the delamination.

• Structural Engineering and Mechanics
• /
• 제4권3호
• /
• pp.243-255
• /
• 1996

This paper presents a model of a layered, delaminated composite beam. The beam is modelled by beam finite elements, and the delamination is modelled by additional boundary conditions. In the present study, the laminated beam contains only one delaminated region through the thickness direction which extends to the full width of the beam. It is also assumed that the delamination is open. The influence of the delamination length and position upon changes in the bending natural frequencies of the composite laminated cantilever beam is investigated.

• 한국정밀공학회지
• /
• 제15권1호
• /
• pp.51-59
• /
• 1998

The purposes of the paper are to consider the failure phenomenon based on delamination and crack when the encapsulant of plastic IC package under hygrothermal loading in the IR soldering process is on elastic and viscoelastic behavior due to the temperature and to show the optimum design using fracture mechanics. The model for analysis is the plastic SOJ package with a dimpled diepad. The package model with the perfect delamination between chip and diepad is chosen to estimate the resistance to fracture by calculating J-integrals in low temperature and C(t)-integrals in high temperature with the change of the design under hygrothermal loading. The optimum design to depress the delamination and crack in the plastic IC package is presented.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
• /
• pp.781-786
• /
• 2000

This paper presents the behavior and strenghening effect of reinforced concrete rectangular beams strengthened sing CFRP sheets with different strengthening level. In general, normally strengthened beams are failed by interfacial shear failure (delamination) within concrete, instead of by tensile failure of the CFRP sheets. The delamination occurred suddenly and the concrete cover cracked vertically by flexure was spalled off due to the release energy. The ultimate load considerably increased with an increase of strengthening level, while the ultimate deflection significantly decreased. The tensile force of CFRP sheets and average shear stress of concrete at delamination failure were curvilinearly proportional to the strengthening level. Therefore, the increment of ultimate load obtained by strengthening was curvilinearly proportional to th strengthening level.

• 한국생산제조학회지
• /
• 제18권4호
• /
• pp.401-409
• /
• 2009

This paper presents a method of calculating the stress intensity factor (K) and crack propagation direction (${\theta}_0$) at the crack-tip that is associated with delamination in the large scale integration(LSI) package. To establish a reasonable strength evaluation method and life prediction, it is necessary to assess fracture parameters under various fracture conditions. Therefore, we conducted quantitative stress singularity analysis considering thermal stress simulating the changes of crack length (a), (h) and (v) in delamination using the 2-dimensional elastic boundary element method (BEM), and from these results predicted crack propagation direction and path.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 추계학술대회 논문집
• /
• pp.139-142
• /
• 2009

In this study, the performance degradation of SOFC single cell caused by the delamination between a cathode and an electrolyte is investigated. As the delamination rate increases, the voltage sharply decreases due to the decrease of reaction sites and losses increase. The current is concentrated to the intact area so that the current density is increased and the ohmic loss and the activation loss become higher. Most part of loss is due to the ohmc loss of electrolyte.