Blog

All about Composite analysis | Abaqus composite

Abaqus composite analysis

All about composite analysis

Composite analysis | Abaqus composite is fully discussed in this post. See the content at a glance:

  • In this course, we will first briefly introduce composite materials.
  • Second, we will learn the role of composite materials in the world and understand why we need them.
  • Third, we will become aware of the composite material categorization in different aspects.
  • And Finally, in what ways and how do we need to analyze composites?

When you enter the engineering world, one of the first things you will hear is “Composite”. Most likely, you hear it in some of your conversations when you talk about your dental problems, buildings, airplanes, etc.

In this blog, you will learn about composite materials from the beginning to advanced. Many of your questions about these materials will be answered. So, be with us until the end and enjoy learning in the engineering world.

1. What is a composite?

In the beginning, I’d like to define the word “composite” in a very simple sentence: Two different materials that just lock together and they’re not dissolved, creating a new material that has properties we need for a specific application.

These two materials have various physical and chemical properties. When they create a composite, the new material will have new properties, unlike the constituent materials. Properties such as becoming stronger, lighter, or electrically resistant.

One of these materials is called “Matrix” which has soft properties compared to the other one. The other material which we could call the “reinforcement” has stiffer and stronger properties compared to the Matrix. The reinforcement part is surrounded by the Matrix, and you may know it as fibers.

composition of composites

 

Some examples of composite materials

  • Human Hair
  • Wood
  • Bone
  • Mud bricks
  • Translucent Concrete
  • Absorbent concrete
  • Fiberglass
  • Carbon Fiber
  • Kevlar

Now that you know what composite material is, let’s talk about “why we need them?”  What are the advantages and disadvantages of these materials?

2. Why do we need composites?

Compared to other common materials, composites are known mostly because of their strength and lightness. Imagine you want to design a plane; you must select a material with properties such as high strength, being as light as possible to fly, and being flexible. Common materials like steel have the strength we need, but they’re heavy and do not have the flexibility we need. Well, the best choice would be composite.

Manufacturers can create qualities that precisely meet the needs of a specific structure for a specific purpose by selecting the right reinforcing and matrix material mix. Take a look at the table below; there are some advantages and disadvantages of these materials.

Composite simulation | Advantage of composite

Some practical examples of composite materials are:

Buildings (e.g., Reinforced concrete with CFRP), bridges, and other constructions, including boat hulls, swimming pool panels, racing car bodies, airplanes, storage tanks, etc. Additionally, they are being employed more and more in standard automotive applications.

Reinforced concrete with CFRP

Reinforced concrete with CFRP

Moreover, you can see them in your house and kitchen. Bathtubs, shower stalls, replica granite, cultured marble basins, and countertops are frequently made of composite materials.

Still with us, right?!

Now, let’s see the composite material classifications.

3. Composite classifications

As we said before, the composites are made of two materials; one is called the “matrix,” and the other is called “reinforcement”. Therefore, the composites can be classified based on two criteria:

  1. Based on the “matrix” material
  2. Based on the “reinforcement” material

Each of them will divide into several types.

The first criterion divides into three types: Organic Matrix Composites (OMCs), Metal Matrix Composites (MMCs), and Ceramic Matrix Composites (CMCs).

The second criterion divides into five types: Particle Reinforced Composites, Flake Reinforced Composites, Fiber Reinforced Composites, Structural Composites, and Nanocomposites.

Don’t worry! We’ll explain them all in the simplest way possible with practical examples.

3.1. Based on Matrix material

The composites are classified into three types based on this criterion:

1. Organic Matrix Composites (OMCs): Generally, OMC refers to two types of composites; Carbon matrix composites which you may know of them by the name Carbon-Carbon composites; and Polymer Matrix Composites (PMCs).

  • Polymer matrix composites (PMCs) have drawn a lot of attention, largely because they are more affordable and have higher stiffness and specific strength than traditional metallic alloys. Additionally, PMCs provide greater design freedom and better corrosion and fatigue resistance. But, they have some disadvantages and the most important of them are low working temperatures, high coefficients of thermal and moisture expansion, and poor elastic characteristics in some directions. The use of PMCs has been well-established in the automotive and aerospace industries for many years, and it is now finding new uses in the biomedical, marine, and infrastructure industries. Now, let’s see some applications of the PMCs:
    • Construction of structural components for satellite systems, space shuttles, and military aircraft.
    • Sporting goods include athletic footwear, sports gear, and other related products.
    • Applications for implants, orthopedic equipment, MRI scanners, X-ray tables, and prostheses in the field of medicine.
    • Protective gear for armor such as bulletproof vests.
    • Body panels, leaf springs, driveshafts, bumpers, doors, etc. are used in the automotive industry.
  • Carbon fibers and carbon matrices make up carbon/carbon composites. Some advantages of these composites are: Withstand in high-temperature situations like up to 6000°F (3315°C), low density, good compressive and tensile strengths, high fatigue resistance, low creep at high temperatures, etc. But like other materials, this one has its own disadvantages as well such as high cost, low shear strength, oxidation vulnerability at high temperatures, etc.

Some applications of Carbon-Carbon composites:

    • Rocket motor nozzle throats and exit cones, nosetips/leading edges, and thermal protection systems are examples of aerospace components that are frequently made from carbon/carbon composite materials.
    • furnace fixturing
    • load plates
    • heating elements
    • heatshields
    • X-ray targets

2. Metal Matrix Composites (MMCs): A composite material called metal matrix composite (MMC) has fibers or particles spread in a metallic matrix made of steel, copper, or aluminum. Usually, a ceramic (such as silicon carbide or alumina ) or another metal (such as steel) makes up the reinforcement phase. Over polymeric matrices, metal matrices have the benefit of being appropriate for usage in applications requiring long-term resistance to harsh conditions. It is true that most metals have higher yield strengths and modulus than polymers. The ability to plastically deform and strengthen metals through numerous heat and mechanical processes is another benefit of using metals. Some advantages of MMCs are high specific strength and stiffness, operating in a wide range of temperatures, being fire resistant,  do not absorb moisture, high compression strength, higher electrical and thermal conductivity compared to PMCs, etc. Several disadvantages of MMCs are the high cost of some material systems, limited service experience, etc. But let’s see some applications of the MMCs:

    • Tank armors
    • Carbide drills
    • In the automotive industry such as driveshaft, engines, and disk brakes.
    • Space systems
    • Pushrods for racing engines
    • In the aircraft components such as the structural component of the jet’s landing gear.

3. Ceramic Matrix Composites (CMCs): In Ceramic Matrix Composites (CMCs), ceramic materials are used for both matrix and reinforcement parts. Any ceramic material can be used to make the matrix and fibers. For example, the matrix can be made of Calcium aluminosilicate and the reinforcement part can be fibers such as carbon or silicon carbide. The advantages of the CMCs are including applications in extreme service temperatures, chemical inertness, high creep resistance and thermal shock, low density, high fracture toughness compared to conventional ceramics, etc. However, these materials have some disadvantages as well, such as shape limitation and part size, brittle fracture, low impact resistance, etc.
Some uses of CMCs are:

    • Turbine blades
    • Bulletproof armor
    • Immersion burner tubes
    • Heat exchangers
    • Rocket propulsion components
    • Turbojet engine components

I didn’t bore you so far, did I?! let’s get to the next criterion.

3.2. Based on Reinforced material

We have five types based on this criterion:

1. Particle Reinforced Composites: Particle-reinforced composites are made up of a matrix that has been strengthened by a dispersed phase made up of particles. Some advantages of this type are including oxidation resistance, these have lower cost and are simpler to produce and construct compared to fiber-reinforced ones, high wear resistance, etc. This one divides into two levels; large particle composites like concrete and dispersion-strengthened composites. Some common examples of this type are:

    • Concrete
    • Particle board
    • Road surfaces

Schematic of Particle Reinforced composite [Ref]

2. Flake Reinforced Composites: This type consists of flat reinforcements of matrices. High out-of-plane flexural modulus, increased strength, and the inexpensive price is a few benefits of this type. However, flakes can’t be easily orientated and there aren’t many materials that can be used. Glass, mica, aluminum, and silver are examples of common flake materials.

Schematic of Flake Reinforced composite [Ref]

3. Fiber Reinforced Composites: This type consists of matrices reinforced by fibers. Just take a look at the figure below to get an idea of what is the fiber-reinforced composite.

fiber reinforced composite

Schematic of Fiber Reinforced composite [Ref]

Regarding the size of the fiber, fiber-reinforced composites are divided into two categories: continuous and discontinuous. When referring to fibers that are as long as the composite material, the phrase “continuous-fiber-reinforced composite” is used, whereas “discontinuous-fiber-reinforced composite” is used to describe fibers that are relatively short in contrast to the size of the composite material. The fibers could be distributed aligned or at random in the discontinuous type. See the figures below to understand better.

[Ref]

The continuous type could be aligned unidirectional,  bidirectional, or even woven.

types of fiber composites

Different types of fiber-reinforced composites [Ref]

In unidirectional composites, all fibers are aligned in a single direction; therefore, despite having high mechanical strength, unidirectional fiber-reinforced composites are weaker under transverse tension than they are under longitudinal tension. So, they shouldn’t be used for parts that need a significant anisotropic strength (strength in all directions). When front-to-back strength is crucial, unidirectional reinforcement is the best option. For instance, unidirectional carbon fiber is frequently used as reinforcement in long, tubular structures that can only move forward and backward, such as boats, rockets, and airplanes.

In bidirectional composites, all fibers are aligned in two unique directions. In this type ultimate strength is low, but occurs in two unique directions. Reduced ultimate strength occurs when characteristics are constant in all directions and the direction of the fibers becomes more statistically varied across the composite.

Woven composites are net-shaped composite structures that are fully interconnected by their yarns. Like a piece of cloth, the yarns are weaved together as warp and weft to create a 3D composite structure.

I know you might get confused with all these categories. But take a deep breath and look at the pictures again. The pictures always help to better understand something.

Now, it’s time to see some practical examples of Fiber-Reinforced Composites (FRCs):

Glass Fiber Reinforced Polymer (GFRP), Carbon Fiber Reinforced Polymer (CFRP), etc. The most common CFRP composite productions are Tennis rackets, golf clubs, softball bats, hockey sticks, and archery arrows and bows. Some applications of GFRP are in Electronic enclosures, Water pipes or drain coverings, and Sporting equipment such as kayaks, Helicopter rotor blades, wind turbine blades, etc.

4. Structural Composites: This type comes into two models; Laminar composites and Sandwich composites.

An assembly of fibrous composite material layers that can be linked to provide the necessary technical qualities, such as in-plane stiffness, bending stiffness, strength, and coefficient of thermal expansion, is known as a composite laminate. Each layer may comprise unidirectional continuous fibers, short fibers, or braided or woven fibers embedded in a matrix. Depending on the projected loading of the structure where the laminate will be utilized, the plies are laid out differently.

Composite laminate [Ref]

composite laminate specimen

A hybrid laminate can be created by layering various materials. The laminate then exhibits anisotropic (with variable direction of principal properties), orthotropic, or quasi-isotropic properties, depending on whether the individual layers are orthotropic (that is, with principal properties in orthogonal directions) or transversely isotropic (with isotropic properties in the transverse plane). Although not limited to isotropic out-of-plane (bending) response, quasi-isotropic laminates show isotropic (i.e., direction-independent) inplane response. The laminate may demonstrate coupling between in-plane and out-of-plane response depending on the order in which the various layers are stacked.

Due to their high strength and lightweight nature, laminated composite materials have become more essential in engineering applications including aerospace and automotive structures.

Sandwich plates are made up of a core covered by facesheets. Due to their high bending stiffness-to-weight ratio, sandwich plates are widely utilized in place of solid plates. The distance between the load-bearing facesheets causes the high bending stiffness; and the core’s lightweight causes the structure lightweight. Each facesheet must be thin in comparison to the core, whether it be an isotropic material or a fiber-reinforced composite laminate. Foam or honeycomb may be used for the core, which must have a material symmetry plane parallel to its midplane and have less in-plane stiffness than the facesheets.

 

[Ref]

Sandwich composite

Now, I’m sure you want to know the applications of these structures:

In aircraft, where mechanical efficiency and weight reduction are crucial, this is a natural application. There are other applications in automotive and transportation.

These prefabricated components are made for use as building envelopes in the building and construction industry. They can be found in commercial and office buildings, clean and chilly spaces, as well as in renovated or newly constructed residential homes. They blend a premium product with significant design freedom. They are generally sustainable and have good energy efficiency.

Polypropylene honeycomb boards and fluted polypropylene boards are used in packing.

I hope you are not bored yet! But don’t worry, we’re going to tell you the final type.

5. Nanocomposites: Materials of the scale of nanometers make up nanocomposites (10–9 m). A constituent must be less than 100 nm in order for something to be considered a nanocomposite. Materials’ characteristics at this size differ from those of the bulk material.
Advanced composite materials typically have microscale components (10–6 m). The majority of the qualities of the resulting composite material are superior to those at the microscale thanks to the use of nanoscale components. However, some nanocomposites’ qualities, like toughness and impact strength, can actually worsen.

Nanocomposite films have improved qualities including elastic modulus and transmission rates for water vapor, heat distortion, and oxygen in packaging applications for the military, among other uses.

 

4. Composite Damage Analysis

In comparison to metals, composites’ damage mechanisms are less well known. Composite materials and structures are susceptible to defects, whether they appear during material processing, component fabrication, or in-service use. Understanding how the damage or defect affects the structural integrity of the composite component is crucial to determining how critical the defect is. If we can somehow determine these damages and tend to them in time, the maintenance cost would be severely decreased. Also, our design will be better and well-optimized.

The composite damages can be classified into two levels:

4.1. Composite damage during manufacturing

Anomalies caused by processing errors like porosity, microcracking, and delaminations are examples of manufacturing damage. Inadvertent edge cuts, scratches, surface gouges, impact damage, and damaged fastener holes are also included. Manufacturing flaws consist of:

  • Voids
  • Air bubbles
  • Delamination
  • Resin starved areas
  • Resin rich areas
  • Wrinkles

Porosity, or the existence of a void in the matrix, is the most typical one. Incorrect or ineffective curing parameters may be to blame for the porosity. Another production flaw is the inclusion of foreign bodies in the matrix, which can be anything from greasy fingerprints to a backing film.

4.2. In-service damage of composites

It’s true that the composite structures have sufficient strength and stiffness but like other structures, they may get damaged during the service. The damages could be caused by impact, low resistance to the service environment, overloading, Staff carelessness, etc.

In-service damages include:

  • Impact damage
  • Fatigue
  • Cracks
  • Delamination
  • Fiber fracturing

Service flaws in composite structures are typically caused by impact damages. Delamination is the most frequent impact-related damage. Delamination occurs when layers in a laminated composite are split, creating a mica-like structure with a considerable loss in mechanical properties. Delamination is the separation of the laminate at the boundary between two layers as a result of shock, impact, or repeated cyclic pressures. Individual fibers can pull away from the matrix, for instance.

It is the engineer’s duty to analyze the structures and determine the defects and damages so that the structure can keep working properly and lower the cost of maintenance. With the help of Computer-aided engineering (CAE) and finite element method (FEM), you would be able to do this task in the best way possible.

We are here at the CAE Assistant to explain some about composite material damage and introduce some FEM tools to simulate these damages correctly. Also, we will help you out learn how to simulate and analyze your model and structure. With our high-quality education, you can learn how to work with the Abaqus and analyze composite structures.

 

 5. Abaqus composite modeling

Until now, you’ve learned so much about composite materials. You’ve learned “what is a composite material?”, “why we need them?”, advantages and disadvantages of composites, classification of composites, and damages in composites. Now, we’re ready to talk about how to model and analyze these magnificent structures in the Abaqus software.

  • First, we talk about how to model a composite in the Abaqus, how to create parts, apply material properties, etc.
  • Second, we talk about how to simulate damage in composites, damage initiation point, progressive damage, and the most important damage theories such as HASHIN criterion, Tsai-Wu, Tsai-Hill, Puck criterion, etc.
  • Third, fatigue in composites.
  • And finally, we’ll see some practical examples and simulations of composite structures in the Abaqus.

If you’re interested as we do and want to learn how to do your projects with the FEM method, let’s get right to it and see how to model composite materials in the Abaqus.

 

5.1. Modeling

As we said, the first step is to model the composite in the software. But you need to know something first. When you want to understand and analyze a complicated material like composite, you look at it from different angles and try to figure out the structure of the model; but what if you check the structure in different scales? Wouldn’t be better?

The understanding of complicated materials utilized in engineering practice can benefit from multi-scale models. In three scales, you can model and analyze a composite structure: Macro (100m), Meso (10-3m), and Microscale (10-6m). Look at the picture below to understand better.

Composite in different scales

Micro-scale (10-6m): RVE analysis is a common method for micro modeling. In composite materials, Representative Volume Element (RVE) is the smallest volume in the structure which represents the values and properties of the whole model. Each measurement that is made on this volume will yield a value that can be representative of the whole model.

Macro-scale (100m):  In macro modeling, instead of separately modeling the components of the composite, the results of the laboratory, as well as the existing theories, suggest that the properties of the composite are introduced to the ABAQUS software in various ways. (common Abaqus composite modeling).

Now, depending on your model and project, you need to choose a scale and start modeling your composite material. Don’t know how and where to start?! Don’t worry! We are here to help you. To start, read Composite simulation (lesson 5).

Need to know more? Check this out:

You can learn composite modeling in Abaqus with the mentioned methods in this package. Also, you learn how to model a woven composite in the Abaqus. This training package provides comprehensive basic information and examples of composite modeling in ABAQUS FEM software. Abaqus composite modeling in Abaqus

5.2. Composite Damage

Like any structure, composites take damage as well due to the manufacturing process or in-service. Composite material behavior is different compared to other common materials. It has bilinear behavior; just take a look at the stress-strain diagram in the figure below to better understand. When a composite material is subjected to a loading condition that passes the elastic area, it reaches the “damage initiation” point; if the loading condition continues, the damage will propagate, and we have the “progressive damage” area, and the damage might propagate till the composite fails.

Stress-strain curve for composite materials

 

In the Abaqus, we must define the “damage initiation” point and the “progressive damage” area; to do so, there are different theories that come in. These theories are categorized into two types: Stress-based and Strain-based.

5.2.1. Abaqus criteria

The Abaqus capabilities of modeling the damage and progressive damage based on different criteria in the GUI limit only to shell elements.

HASHIN criterion: 

In the below package, all available criteria on Abaqus about composites are introduced, and there are some workshops that teach you how to model correctly in Abaqus. Both stress-based and strain-based theories are presented in this package.

Abaqus composite damage

 

5.2.2. HASHIN criterion for 3D elements

There are different criteria for damage initiation as well as how to reduce the mechanical properties. Three-dimensional HASHIN damage, which involves detecting damage to fibers, matrix, and delamination, is very common. It should be mentioned that progressive damage can be done by reducing the properties suddenly or gradually with different energy methods or equations.

HASHIN damage HASHIN damage

5.2.3. TSAI criterion for 3D elements

There are also some tutorial packages in this field that will be available on the CAE assistant shop soon.

5.2.4. Puck criterion

There are also some tutorial packages in this field that will be available on the CAE assistant shop soon.

5.2.5. Hybrid composite

There are also some tutorial packages in this field that will be available on the CAE assistant shop soon.

 

5.3. Composite fatigue

The primary failure mechanism for structures subject to cyclic loading is fatigue. You can see the fatigue load classification in the figure below:

[Ref]

We can determine the composite fatigue life by the strain, stress, or energy approach. Here we have fatigue analysis of unidirectional composites with the UMAT and VUMAT subroutines which use the Shokrieh fatigue theory; Also, there are fatigue analyses of woven composite, short fiber composite, and Balsa wood.

5.3.1. Unidirectional composite

 

Composite Fatigue Subroutine Fatigue analysis with VUMAT subroutine

5.3.2. Woven composite

In this training package, the modified Hashin fatigue damage model based on the article titled  “Life prediction of woven CFRP structure subject to static and fatigue loading “ is used. In this fatigue model, strength and elastic properties reduction and fatigue life are calculated. Woven composite fatigue

5.3.3. Short fiber composite

The fatigue simulation of short fiber composites with subroutine package is based on “Fatigue behavior and cyclic damage of peek short fiber reinforced composites”  article, and the subroutine has been implemented based on the mentioned article. However, this article has used the USDFLD subroutine, but we use the UMAT subroutine, which is more accurate than USDFLD since the material strength and properties reduction is smooth. short fiber composite fatigue

5.3.4. Wood

This training package focus on writing subroutines to simulate wood fatigue in Abaqus. In the “Balsa wood fatigue simulation with subroutine” package, the used fatigue theory of wood has been described. Then, the flowchart of the subroutine and writing subroutine line-by-line is explained. It helps users to develop the subroutine based on customized theory. Finally, the subroutine is implemented on the Abaqus model, and the results are discussed. Wood fatigue simulate in Abaqus

5.4. Composite structure

Due to the increasing growth of science and industry, there is a need to develop advanced materials with more profits. Composite materials due to higher efficiency and economic benefits have become a suitable alternative to traditional materials in various industries. Therefore the development of these materials by understanding how to produce and study their properties is essential. The composites are used in many fields such as pressure vessels, aerospace, military, civil structures, etc.

5.4.1. Composite pressure vessel

pressure vessel composite Composite pressure vessel in ABAQUS-package

 

 

 

 

 

 

 

One thought on “All about Composite analysis | Abaqus composite

  1. nina82 says:

    Hello, thank you for this useful article. I learned a lot of good points about the analysis of composite materials.
    Do you recommend me any training package for the analysis of chopped composite materials?
    thank you

Leave a Reply