The Influence of Non-Traditional Composite Laminates on Open-Hole Tension Strength

2007 ◽  
Author(s):  
D. P. Stone ◽  
L. V. Smith ◽  
A. Kothidar
Keyword(s):  
Strain Field ◽  
Composite Laminates ◽  
Damage Evolution ◽  
Adhesive Bonding ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Strain Measurements ◽  
Stress Risers ◽  
Open Hole ◽  
Increased Strength

Composite materials are commonly used in applications with a need for increased strength or reduced weight. The composite structure is often attached using mechanical fasteners, even in cases where adhesive bonding is prevalent. The strength of the composite is typically reduced by large factors in the presence of these stress risers. The following considers the sensitivity of non-traditional layups to stress concentrations in the form of open-hole tension. The effects are described numerically and experimentally using finite element analysis and spatial strain measurements, respectively. Improvements in strength exceeding 10% from this preliminary exercise suggest that tailoring fiber orientations may have potential to minimize the effect of stress concentrations. Consideration of the strain field in the vicinity of the hole showed evidence of damage evolution within approximately 25% UTS for many of the laminates. The maximum strain failure criterion was able to describe the onset of damage or yield for the laminates considered here.

Temperature effect on the tensile behaviors of carbon/polyimide composite laminate

2016 ◽  
Vol 231 (24) ◽  
pp. 4592-4602 ◽  
Author(s):  
Liang Li ◽  
Purong Jia ◽  
Wenge Pan
Keyword(s):  
Temperature Effect ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Thermomechanical Coupling ◽  
Single Element ◽  
Element Analysis ◽  
Open Hole ◽  
Dimensional Finite Element ◽  
Different Temperatures ◽  
Three Dimensional Finite Element

Experimental and numerical investigations were carried out to study the temperature effect on the stiffness, strength, and failure behaviors of carbon/polyimide composite laminates. Both unnotched laminates and open-hole laminates were tested under tension load at three temperatures (room temperature, 200 ℃, and 250 ℃). A three-dimensional finite element analysis was carried out to study the thermomechanical coupling behavior in the notched laminate. The model considers each layer and interface as a single element in the thickness direction so that in-plane stress and interlaminar stress could be analyzed in the model. The stresses around the open-hole changing characteristics with the temperature and tensile loading have been discussed in detail. Failure analysis was carried out to predict the residual strength of the notched laminates at different temperatures. Compared to the experimental data, the numerical results have an excellent agreement.

scholarly journals Damage Monitoring and Analysis of the Structure Effect on Strength of Composite Laminates

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Chia-Chin Chiang ◽  
Liren Tsai ◽  
Vu Van Thuyet
Keyword(s):  
Composite Laminates ◽  
Composite Structures ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Element Analysis ◽  
Damage Propagation ◽  
Whole Process ◽  
Initial Damage ◽  
Open Hole ◽  
Cfrp Composite

Carbon fiber reinforced polymer (CFRP) composite materials have been widely used in industries in recent years. The design of composite structures, and open-holes for joining are also widely used. Understanding of open-hole behavior is very necessary for the design of complex structures. In this paper, the initial damage, progressive damage analysis, and the effect of structure on strength of composite laminates are investigated. Based on Hashin’s criteria, three-dimensional model of composite laminates containing a central open-hole is developed. The model is conducted by finite element analysis, commercial Abaqus software to simulate the whole process of initial damage, propagation of damage, and analysis of the effect of a few structures on strength of composite laminates containing open-hole.

scholarly journals Open holes in composite laminates with finite dimensions: structural assessment by analytical methods

2022 ◽  
Author(s):  
M. Nguyen-Hoang ◽  
W. Becker
Keyword(s):  
Failure Analysis ◽  
Analytical Methods ◽  
Composite Laminates ◽  
Design Feature ◽  
Potential Method ◽  
Finite Width ◽  
Efficient Computation ◽  
Stress Concentrations ◽  
Open Hole ◽  
Circular Holes

AbstractOpen circular holes are an important design feature, for instance in bolted joint connections. However, stress concentrations arise whose magnitude depends on the material anisotropy and on the defect size relative to the outer finite plate dimensions. To design both safe and light-weight optimal structures, precise means for the assessment are crucial. These can be based on analytical methods providing efficient computation. For this purpose, the focus of the present paper is to provide a comprehensive stress and failure analysis framework based on analytical methods, which is also suitable for use in industry contexts. The stress field for the orthotropic finite-width open-hole problem under uniform tension is derived using the complex potential method. The results are eventually validated against Finite-Element analyses revealing excellent agreement. Then, a failure analysis to predict brittle crack initiation is conducted by means of the Theory of Critical Distances and Finite Fracture Mechanics. These failure concepts of different modelling complexity are compared to each other and validated against experimental data. The size effect is captured, and in this context, the influence of finite width on the effective failure load reduction is investigated.

Review on the Fatigue of Composite Hybrid Joints Used in Aircraft Structures

2014 ◽  
Vol 891-892 ◽  
pp. 1591-1596 ◽  
Author(s):  
Nabil Chowdhury ◽  
Wing Kong Chiu ◽  
John Wang
Keyword(s):  
Composite Materials ◽  
Composite Laminates ◽  
Adhesive Bonding ◽  
High Stress ◽  
Real Life ◽  
Engineering Industry ◽  
Stress Concentrations ◽  
Static Testing ◽  
Hybrid Joints ◽  
Mechanical Fastening

The use of composite materials as a replacement for commonly used metals such as aluminium and steel are increasing in the engineering industry, particularly in the aerospace sector. The move towards light weight and high stiffness structures that have good fatigue durability and corrosion resistance has led to the rapid move from metal to composites. This change allows for further flexibility in design and fabrication of various components and joints. There are three main categories of joints used in composite materials – mechanically fastened joints, adhesively bonded joints and the combination of the two called hybrid joints. In order to adequately understand the effectiveness of these joints, substantial testing and validation is required, particularly in the use of hybrid joints for real life applications. Static testing, load distribution and parametric studies of hybrid joints have been investigated by various researchers; however further work is still required in understanding the durability and fatigue of hybrid joints and ensuring that both the adhesive and mechanical fasteners can work together effectively in producing an optimum joint. Mechanical fastening alone in composite laminates is not a preferred joining method as they create high stress concentrations around the fastener holes. Adhesive bonding although has numerous benefits it is difficult to detect the bond defect particularly in cases where weak bonds can occur during applications and it is sensitive towards the environmental conditions. Thus hybrid joints are seen arguably as being more effective in joining composite components together and offer greater residual strength. Hence the performance, strength and long-term durability of these joints need to be further investigated and be applied to practical situations whilst assisting in repair certification.

Numerical modelling of multi-material graded joints under shear loading

2020 ◽  
Vol 234 (5) ◽  
pp. 436-445
Author(s):  
Mateus Q dos Reis ◽  
Ricardo JC Carbas ◽  
Eduardo AS Marques ◽  
Lucas FM da Silva
Keyword(s):  
Numerical Model ◽  
Joint Strength ◽  
Adhesive Bonding ◽  
Numerical Models ◽  
Shear Loading ◽  
Lap Joints ◽  
Functionally Graded ◽  
Stress Concentrations ◽  
Adhesive Properties ◽  
Element Analysis

Due to environmental concerns, modern transportation solutions demand drastic reductions of fuel consumption and emissions, which can only be achieved with advanced structures using high-performance lightweight materials. For joining these dissimilar materials, adhesive bonding appears as an optimal solution, since mechanical fastening adds weight to the structure, and welding technology is not easily applicable to reinforced plastics and composites. However, one of the major drawbacks associated with bonded joints is the presence of stress concentrations at the overlap ends, especially in single lap joints. In order to reduce these stress concentrations, several techniques have been developed. One of these is the functionally graded adhesive, in which the adhesive properties gradually vary along the overlap length, leading to a more uniform stresses distribution and improving the joint strength. However, the manufacture of an adhesive layer with properties which gradually vary is complex in practice and so is the creation of numerical models that represent these configurations. In the present work, a numerical model for different-graded distribution of adhesive properties along the overlap was developed, using programmed step functions on finite element analysis background in order to discretize and simplify the continuous properties distribution gradient. Cohesive zone modelling was introduced in the numerical model, enabling it to effectively predict graded joint strength. The model was validated with experimental results of functionally graded joints available in the literature. The numerical model developed presents itself as a powerful tool to predict joint strength for functionally graded joints, without imposing large computational demands.

Effective Convergence Checks for Verifying Finite Element Stresses at Two-Dimensional Stress Concentrations

2016 ◽  
Vol 1 (4) ◽  
Author(s):  
G. B. Sinclair ◽  
J. R. Beisheim ◽  
P. J. Roache
Keyword(s):  
Finite Element ◽  
Error Estimation ◽  
Accurate Determination ◽  
Benchmark Problems ◽  
Two Dimensional ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Stress Risers ◽  
Stress Concentration Factors

The accurate determination of stresses at two-dimensional (2D) stress risers is both an important and a challenging problem in engineering. Finite element analysis (FEA) has become the method of choice in making such determinations when new configurations with unknown stress concentrations are encountered in practice. For such FEA to be useful, discretization errors in peak stresses have to be sufficiently controlled. Convergence checks and companion error estimates offer a means of exerting such control. Here, we report some new convergence checks to this end. These checks are designed to promote conservative error estimation. They are applied to seven benchmark problems that have exact solutions for their peak stresses. Associated stress concentration factors span a range that is larger than that normally experienced in engineering. Error levels in the FEA of these peak stresses are classified in accordance with: 1–5%, satisfactory; 1/5–1%, good; and <1/5%, excellent. The present convergence checks result in 91 error assessments for the benchmark problems. For these 91, errors are assessed as being at the same level as true exact errors on 83 occasions and one level worse for the other 8. Thus, stress error estimation is largely accurate (91%) and otherwise modestly conservative (9%).

scholarly journals Evaluation of the Ko-Len Model for Enterlaminar Stresses in Composite Laminates with an Open Hole

1996 ◽  
Vol 5 (5) ◽  
pp. 096369359600500 ◽  
Author(s):  
F. Z. Hu ◽  
C. Soutis
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Tensile Loading ◽  
Stress Distributions ◽  
Element Analysis ◽  
Open Hole ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The purpose of this paper is to evaluate a recently developed analytical model [1] which determines the interlaminar stress distributions around a circular hole in symmetric composite laminates under in-plane tensile loading. For this purpose, a three-dimensional finite element analysis is performed and the stress distributions for symmetric cross-ply laminates are presented This work is relevant to the prediction of delamination onset load and location around the discontinuity.

Design and performance of bonded patch repairs of composite structures

1997 ◽  
Vol 211 (4) ◽  
pp. 263-271 ◽  
Author(s):  
C Soutis ◽  
F Z Hu
Keyword(s):  
Composite Laminates ◽  
Composite Structures ◽  
Three Dimensional ◽  
Patch Repair ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Premature Failure ◽  
Patch Repairs ◽  
And Performance ◽  
Three Dimensional Finite Element

The compressive behaviour of bonded patch repaired composite laminates is examined. A non-linear stress analysis is performed on a double-lap joint in order to identify critical joint parameters and design an efficient external patch repair. It is found that oversized patches not only increase the structure's weight but also increase the stress concentrations in the repaired region which can cause premature failure. Reducing the patch thickness near the edges of the overlap and increasing the local adhesive thickness decreases the stress concentration in both shear and peel stresses. A three- dimensional finite element analysis is then performed to determine the stresses in the optimum repaired configuration and is used with a stress failure criterion to predict the ultimate failure load. Experimental measurements show that carefully designed bonded patch repairs can recover almost 80 per cent of the undamaged laminate strength.

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