Composite Materials
Composite Materials
Composite Materials
FOCUS
WHY COMPOSITE MATERIALS? WHAT IS COMPOSITE MATERIAL? DIFFERENT CONSTITUENTS & THEIR FUNCTIONS ADVANTAGES & DISADVANTAGES OF COMPOSITE MATERIALS HOW THEY ARE DIFFER FROM METALS? SOME OF THE APPLICATIONS
Function of Structure
Basically, to:
Transmit & resist applied loads. Provide aerodynamic shape. Protect crew, passengers, payload, systems, etc.
Most of the a/c, use of semi-monocoque design (thin, stressed outer shell with additional stiffening members) for wing, fuselage & empennage.
DESIGN DRIVE
SAFTY
STRUCTURE PASSENGER
PERFORMANCE
MISSION FUEL
COST
PRODUCT OPERATION & MAINTENANCE
Weight breakdown
Structure 30%
COMPOSITE COMPONENTS STRUCTURAL WEIGHT : 30% SURFACE AREA : 70% WEIGHT REDUCTION : 130 Kg.
SPINE COVERS
FUSELAGE FRAMES
WING SKINS
WING SPARS
TOP FLOOR
GLARE SHIELD
COMPOSITE COMPONENTS
STRUCTURAL WEIGHT : 45% SURFACE AREA : 90% WEIGHT REDUCTION : 485 Kg.
THE AIRFRAME
The airframe consists of components such as
wing upper wing lower fuselage skin spars, frames, ribs landing gear control surfaces.
Essentially, the airframe is required to resist applied loads, provide an aerodynamic shape and protect passengers, payload and equipment from the external environmental conditions. Each component has different specific constraints, resulting in different material selection criteria for each component.
COMPOSITE MATERIALS
COMPOSITE MATERIALS
Two or more materials combined on a macroscopic scale to form a useful material Ideal for structural applications where high strength to weight and stiffness-to-weight ratios are required Conventional composites limited to in-plane distributed loads
Matrix
Protect the reinforcement Gives shape to the component Local load transfer Decides the manufacturing process
Classification of Composites
REINFORCEMENT
Particulate
Large Dispersion Particle Strengthened continuous
Fiber
Discontinuous
Unidirectional
Bi-directional
Aligned
Random
TYPES OF COMPOSITES
ADVANCED COMPOSITES
FIBER REINFORCED FIBERS
CARBON KEVELAR GLASS
MATRIX
EPOXY POLYIMIDE POLYESTER
WHY FIBERS?
2500
BO N
2000
CA RB ON
1500
IM C
S AS GL
AR
1000
AM AR
HS
ID
500
S AS L EG
TENSILE STRAIN %
2000
ON
CA
RB
O N
HS
1500
CA RB
S AS GL
1000
IM
500
AR
D MI A
ASS L EG
2 3 4
COMPRESSIVE STRAIN %
REINFORCEMENT FORMS
PREPREG UD TAPES
All the filaments are oriented in one direction. The tape is fabricated in width ranging from 3 to 60 inches and is supplied in rolls. Unidirectional tape works well when maximum performance is required in one direction. Tapes are made by careful alignment of side-by-side yarns; usually of 1420 or greater denier. Tapes are usually impregnated with resin and are available from many prepreg suppliers.
Unidirectional Weave
Unidirectional Weave Cloth (95% - 0, 5% - 90) This cloth has 95% of its filaments in the warp direction (length direction) and 5% in the fill direction to facilitate material handling. Its strength is approximately equal to unidirectional tape. It is fabricated and available up to 72 inches in width. This weave has the general characteristics: 1) maximum strength in one direction and 2) minimum strength in the transverse direction.
Plain Weave
The oldest and most common basic textile weave in which one warp end (lengthwise thread) weaves over and then under one filling pick (crosswise thread). This weave has the general characteristics: a. Firmest and most stable of the industrial weaves. b. Affords fair porosity with minimum yarn slippage. c. Uniform strength pattern in all surface directions. d. Affords ease of air removal in hand layup or molding.
Basket Weave
This weave is similar to a plain weave, but it has two or more warp ends weaving as one end over and under two or more filling picks weaving as one pick. This weave has the general characteristics: a. Less stable than a plain weave. b. More pliable than a plain weave. c. Flatter and stronger than an equivalent weight and count of plain weave.
OTHER FORMS
MATRIX
Polymer matrix
Thermoset
Epoxy Polyester Phenolics Polyimide
Thermoplastic
PEEK PES
LAMINATE
ADVANTAGES COMPOSITES
HIGHER SPECIFIC STRENGTH & MODULUS
LIGHT WEIGHT PERFORMANCE FUEL EFFICIENT
TAILARABILITY / ANISOTROPIC
OPTIMUM WEIGHT & PERFORMANCE
EASY MANUFACTURING
COST
CONCERNS
BRITTLENESS
POOR IMPACT PERFORMANCE STRESS CONCENTRATION
PROCESS SENSITIVE
SENSITIVE TO PROCESS PARAMETERS VARIATION / SCATTER
COST
Laminated structures
Easy characterization Simple failure modes Easy to analyze Limited potential for optimization
Many properties Complex failure mode Complex analysis Large Potential for optimization
KEVLAR PREPREG
Stress strain Yielding indication of failure Chip formation drilling Better joints - redistribution of stress Low stress concentration
Stress strain
Catastrophic failure Dust - drilling (Kevlar) Difficult to join High stress concentration
HETROGENEOUS
UNLIMITED LIFE WHEN STORED PROPERLY PROPERTIES DOES NOT CHANGE WITH TIME LOWER INVENTORY COST
LIMITED USABLE LIFE EVEN WHEN STORED @ -18 DEG C PROPERTIES CHANGES RAPIDLY WITH TIME HIGH INVENTORY COST
SHELF LIFE POT LIFE OUT LIFE GEL TIME
ARTIFICIAL LIMBS
SPORTS
Conclusions
Composite materials are increasingly used in civil & military aircraft Large potential for weight reduction & part integration Enables safe, low maintenance structure Reduces fuel consumption and improves performance in aircraft Impact performance & low through the thickness strength are the concerns Further cost reduction is contemplated through cost effective manufacturing processes.