Bài giảng Mechanics of Composite Material_9_2015

Mechanics of Composite
Materials
Assoc. Prof. Dr. Nguyen Trung Kien
Email: ,
Faculty of Civil engineering and Applied mechanics
HCMC University of Technology and Education
1 Vo Van Ngan Street, Thu Duc District, Ho Chi Minh City, Vietnam
September 2015


Contents
2

Introduction to composite materials
Mechanical behaviors of composite materials
Elastic behaviour of unidirectional composite materials
Elastic behaviour of orthotropic composite
Off-axis behaviour of composite materials
Fracture and damage of composite materials
Modeling of mechanical behaviours of laminated plates
Homogenization of composite materials


References
3

Jean-Marie Berthelot, Composite Materials–Mechanical
behavior and Structural analysis, Springer, 1999
J. N. Reddy, Mechanics of laminated composite plates
and shells–Theory and Analysis, CRC Press, 2004
Autar K. Kaw, Mechanics of Composite Materials,

Taylor & Francis, NewYork, 2006
S.
LI,
Introduction
to
micromechanics
nanomechanics, Lecture notes.

and


Significance & Objectives
4

Investigation of characteristics of the constituent and
composite materials
Material optimization
Development of analytical procedures for determining
material properties
Development of analytical procedures for determining
material properties
Development of analytical procedures for determining
structural behavior


Contents
5

Introduction to composite materials
Mechanical behaviors of composite materials

Elastic behavior of unidirectional composite materials
Elastic behavior of orthotropic composite
Off-axis behavior of composite materials
Fracture and damage of composite materials
Modeling of mechanical behaviors of laminated plates
Homogenization of composite materials


INTRODUCTION TO COMPOSITE MATERIALS
6

Introduction
Composite materials
o Matrix materials
o Fibers
o Architecture of composite materials
o Study the mechanical behavior of composite
materials
Application of composite materials


Composite materials
7

Old and new aspects of
composites
o Human body, plants
o Early 1960s (fibrous composites)

Definition:

“Composite” means "made of two or
more different parts
heterogeneous
All materials may be considered
heterogeneous if the scale of interest is
sufficiently small
Fibrous composites (Fiber-Reinforced
Composites) are materials in which one
phase acts as a reinforcement of a second
phase


Composite materials
8

Classification:
o Form of constituents
Fiber composite
Particle composite

o Nature of Constituents
Organic matrix composites
Metallic matrix composites
Mineral matrix composites

Particle composite

interphase Continuous phase (matrix)
Dispersed phase
(reinforcement)

Fiber composite


Composite materials
9

Classification by class of constituents

Fiber Reinforcement

Particle

Matrix

Composite

Matrix

Composite

Mechanical properties of composites
nature of the constituents
proportions of the constituents
orientation of the fibers


Properties of composite materials
10

Low-medium performance composites

The reinforcement provides stiffening and local strengthening of
the materials (short fiber)
The matrix is the main load bearing constituent governing the
mechanical properties
High performance composites
The reinforcement is the backbone of the materials (continuous
fiber)
The matrix provides protection and support for the sensitive fiber
The interphase controls the failure mechanisms


Geometric and physical definitions
11

Homogeneity
Its properties are the same at every point
(independent of location)
Nonhomogeneity (heterogeneity)
Its properties vary from point to point (depend on
location)
Isotropy
Its properties are the same in all directions
(independent of the orientation)
Anisotropy
Its properties at a point vary with direction (depend on
orientation)


Macroscopic/Microscopic
12

Macroscopic: homogeneous and anisotropic
Microscopic: nonhomogeneous and isotropic

a
b

A
B

2015-09-09


Definition of Composites
13

Nonhomogeneous anisotropic

isotropic

No conventional method
Structural analysis tool for composites required

orthotropic

anisotropic

2015-09-09

MATRIX
14

Polymer
Metal (higher use temperature)
Ceramics (very high use temperature)


MATRIX
15

Matrix: a resin (polyester, epoxide, etc.) and fillers which
is to improve the characteristics of the resin:
o Thermosetting Resins:
Polyester Resins
Condensation Resins
Epoxide Resins

o Thermoplastic Resins:
polyvinyl chloride (PVC), polyethylene, polypropylene, polystirene,
polyamide, and polycarbonate

o Thermostable Resins:
o Bismaleimide Resins, Polyimide Resins


MATRIX - RESIN
16

Any resin system for use in a composite material

will require the following properties:

1. Good mechanical properties
2. Good adhesive properties
3. Good toughness properties
4. Good resistance to environmental degradation


Composite materials
17

Epoxide Resins:

Advantages of epoxide resins are the following:
good mechanical properties (tension, bending, compression, shock, etc.)
superior to those of polyesters
good behavior at high temperatures: up to 150-190°C in continuous use
excellent chemical resistance
low shrinkage in molding process and during cure (from 0.5-1 %)
very good wettability of reinforcements
excellent adhesion to metallic materials

Disadvantages:
High cost, manufacture, sensibility to cracking


Composite materials
18

Polypropylene, polyamide:

Advantages of epoxide resins are the following:
low cost, fabrication
Disadvantages:
mechanical and thermomechanical properties : low

Limited development
Thermostable Resins: Bismaleimide Resins, Polyimide Resins
Thermal performance developed especially in the aviation and space


Composite materials
19

Fillers and additives: function of improving the mechanical and
physical characteristics of the finished product or making their manufacture
easier

Fillers: Reinforcing Fillers, Nonreinforcing Fillers
o Reinforcing Fillers : improve the mechanical properties of a resin
Spherical fillers: diameter usually lying between 10 and 150µm. They can be
glass, carbon, or organic (epoxide, phenolic, polystirene, etc.),
Nonspherical fillers: mica used most (dimension: 100-500µm, thickness: 1-20
µm)

o Nonreinforcing Fillers: reducing the cost of resins, preserving their
performance
carbonates, silicates

Additives: pigments and colorants, antishrinkage agents,

antiultraviolet agents


Composite materials
20

Fibers:
Improve mechanical characteristics: stiffness,strength, hardness, etc
Improve certain of the physical properties: thermal properties, fire
resistance, resistance to abrasion, electrical properties
Reinforcements origins: vegetable, mineral, artificial, synthetic
fibers
linear forms (strands, yarns, rovings, etc.)
surfacing tissues (woven fabrics, mats, etc.)
multidirectional forms (preforms, complex cloths, etc.)


Composite materials
21

Specific mechanical characteristics of materials, made
in the form of fibers


Composite materials
22

Specific mechanical characteristics of materials, made
in the form of fibers

Composite materials
23

Architecture of composite materials
Laminates


Composite materials
24

Architecture of composite materials
o Sandwich


Composite materials
25

Laminated composite materials