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# 37

PART 1

§1 Composite materials normally consist of a continuous matrix 1) , which is often a synthetic resin, and a fibrous reinforcing structure. The reinforcement has high strength and stiffness, while the matrix binds (2) the fibres together allowing stress to be transferred from one fibre to another and producing a consolidated structure. Correctly designed and competently manufactured products in advanced composites can show benefits over metals in such features as weight, performance, and improved fatigue and corrosion resistance.

§2 In advanced or high-performance composites, high strength and high modulus (3) fibres are used in relatively high volume fractions while the orientation of the fibres is controlled to enable high mechanical stresses to be carried safely. In fact, the major advantage of these materials lies in their anisotropic (4) nature. The reinforcement can be oriented to follow the stress patterns (5) in the component, leading to much greater design economy than can be achieved with traditional isotropic (4) materials. Since the strength and stiffness of products made from these composite materials is governed by the fibres, controlling their disposition is critical.

§3 Reinforcing fibres for advanced composites are typically glass, carbon and aramids (6). Glass fibres are made by a melting and drawing process from a variety of glass compositions. The process used depends on the properties required: heat resistance or chemical resistance, for example. Carbon fibres on the other hand, are made from pre-existing filaments such as synthetic acrylics, or from pitch (7) which is converted to carbon fibres by oxidation and carbonisation at high temperature. The aramids are related chemically to nylon fibres but exhibit much higher strength and stiffness at high temperatures. Typical properties of the fibres are given in the adjacent table.
 
 

fig.1 Properties of reinforcing fibres
 

PART 2

§4 The benefits which accrue from (8) the use of composites have found ready acceptance (9) by the aerospace industry where weight considerations are usually most important. We therefore find many structural parts of aircraft made from glass, carbon and hybrid composites. The greater fatigue life of composites also prompted ( 10) their use in such vital parts as helicopter rotor blades (11) where the UK has a significant lead.

§5 The electrical insulating characteristics of glass reinforced composites, coupled with their structural characteristics, have also brought economies and better performance in insulators, switchgear (12) and generator and transformer parts.
 
 

§6 The defence industries now make extensive use of composites because of lightness, corrosion resistance, freedom from magnetic and eddy current (13) response and freedom form maintenance problems. The leisure industries have also benefited from some of these characteristics. The use of advanced composites for golf clubs, fishing rods, tennis racquets and skis has become popular because of lightness, stiffness and elastic properties.

Vocabulary notes:

1 - matrix (plural: matrices) : matrice
2 - to bind : to link
3 - modulus : module
4 - anisotropic : the material does not exhibit the same properties in every direction (<> isotropic)
5 - pattern : regular arrangement or lay out
6 - aramid : a polymere similar to nylon
7 - pitch : résine
8 - to accrue from : (here ) to derive from, result from
9 - find ready acceptance : to be quickly accepted
10 - to prompt their use = (here) be a significant argument for using
11 - blade : pale d’hélicoptère
12 - switchgear : switch + gear (a gear = an intrument, equipment)
13 - eddy current : courants de Foucault

BRAINSTORMING

Have you ever heard of composite materials ? What are their characteristics? What are they used for?
 
 

PREPARE FOR UNDERSTANDING THE TEXT
 

1 - Global comprehension

a- Look at the opening sentence of each part and say which part of the text is a/ about the composition of composite materials b/ the use / applications of composites

b- Read the opening sentence of paragraphs 1 to 3 and say whether each paragraph tells about a/ the composition of composites, generally speaking ? b/ fibres? c/ matrix ? d/ another topic ?
 

2 - Look for occurrences of ‘to’ in paragraphs 1,2,3. and say when

• to + verb ( = to + base verbale ) is required after some verbs ( cf. I want to do... – he tried to stop);
• to + verb expresses purpose ;
• to is a preposition indicating location or direction (cf. go to the station);
• to is a preposition used after some verbs / adjectives. (cf. it’s easy to assemble – one thing leads to another - )

3 - Linkwords

a. Pick up English linkwords meaning:
§1, §2 tandis que, alors que (This linkword may have another meaning ? Which one ?) – §2 étant donné que, puisque (This linkword may have another meaning ? Which one ? Which one is the more usual in technical English ?) – §4 par conséquent – §6 à cause de

b Which linkword could have been inserted before ‘leading’,  thus making the meaning clearer § 2) ?
 

4 - Pick up comparatives ( § 3,4,5.)
 

5 - Compound words

a Pick up compound adjectives with the pattern :

§1 adverb + past participle – §5 noun + past participle

b. How do you understand " improved fatigue and corrosion resistance " (§1) :

• (they) improved resistance to fatigue + (they) improved resistance to corrosion ?
• (they) improved fatigue + corrosion  (became) resistant ?
• (they have) improved = better resistance to fatigue + (they have) improved = better resistance to corrosion ?
• (they have) improved = better resistance to corrosion +  (they have)  improved = better fatigue  ?

6 - Vocabulary

a - Word building : from adjectives to nouns.

• adjective + NESS = noun. Do not confuse with the suffix –LESS (= without).

What quality does something brittle (= fragile), rough, tough exhibit?

• adjective ( often with spelling modifications) + TH = noun.

Give the corresponding noun : deep, wide, high

• What are the nouns corresponding to: tensile, elastic, dense, plastic

b - Are you sure you understand these words?

§1 improved (...) resistance (What is the corresponding noun?)
§2 ... is controlled to enable high mechanical stresses to be carried safely...
§2 their disposition is critical
§3 (they) exhibit
§4 the UK has a significant lead

READING COMPREHENSION

7 - §1 a - Fill in the table
 

The components of composites
The components’ qualities and properties

b - List the advantages of composites over metal

• The paragraph is concerned with ordinary quality composites.
• These composites require using important proportions of high strength and high modulus fibres.
• Orienting the fibres is essential
• When a material is mechanically stressed, safety tests must be carried out
• The orientation of fibres that is directly related to / with ?? the mechanical properties of the material.
• Being anisotropic proves to be a very positive feature....
• because it is possible to place reinforcement exactly where stress appears
• Traditional isotropic materials are however more economical
• Traditional isotropic materials will be heavier and / or less resistant for the same weight
• With traditional materials the design is simpler and more economical...
• this is so because the reinforcement can be placed exactly where there is stress.
• Controlling fibre orientation is essential to design very resistant and very stiff materials.

• What materials can be used as reinforcing fibres ?
• Material 1 : what production process is used? What are the criteria for choosing between the two processes ?
• Material 2: What is it made from? What have you learnt about the production process concerning pitch?
• Material 3: what differences are there between aramid and nylon?

10 - § 4,5,6 Fill in the table. (a) list the industries mentioned in the text - (b) list the uses of composites – (c) list the reasons for using them.
 

(a) industries
(b) uses			///////////////////////////////
(c) reasons

 
 
 

LANGUAGE STUDY

11 -
a - Look at the table above ( §3) and read it using to range between ... and .../ to range from ... to ... / to vary from ... to ...
(Note : 'ca' [ latin : circa ] = about, approximately)

b - Express the various properties with comparatives and superlatives
 

12 - Look again at paragraphs 4,5 and 6 and at the table you have filled in ( exercise 10), then make a list of the properties:
 

mechanical	electrical	magnetic

 

Express the advantages of these properties. You can use some of the following phrases:

• It offers / shows (great) benefits in terms of +noun
• It offers advantages over + noun
• It is (outstandingly) suitable for + noun / + ING
• Another feature is
• It has a number of advantages
• The major advantage lies in + noun / + ING
• It avoids + ING
• It eliminates the need for + noun / + ING
• One of the interesting features is that + subject + verb
• The advantage/ the (net) result is that + subject + verb

• It is critical to control the disposition of the reinforcements.<--> Controlling the disposition of the reinforcements is critical.

• Give the other form
  -It is now usual to find composites in planes-It would be near-impossible to achieve special profiles without advanced composites.
  -It is essential to obtain high degrees of fibre alignment.
  -It is often necessary to pre-impregnate the fibres.
  -It is easy to control the hardening conditions of thermosetting resins.
  -it is necessary to be more familiar with this new technology.

14 - Linkwords. Replace each linkword by another one (several possibilities) and make the necessary changes.

§2 while the orientation …
§2 since the strength…
§3 but exhibit ...
§3 such as synthetic acrylics
§4 we therefore find …
§4 such vital parts as helicopter rotor blades…
§6 the leisure industries have also benefited …

15- Turn this text  into the passive
 
 

PULTRUSION PROCESS  Engineers can achieve a wide range of fibre aligned profiles by the pultrusion process in which they pull the reinforcement through a bath of liquid resin and into a heated metal die. They cure the resin within the die and they use the emerging profile to effect the pull. Industry is now using pultruded profiles in a number of applications.

fig. 2 Pultrusion process Vocabulary: die : filière, matrice to cure : donner une  strand : brin (d'un fil)

16 - How to express purpose.

a. In exercise 2 you have seen that ‘to’ can be used to express purpose.
Here are other ways to mean the same : with the aim of + ING – with a view to + ING – to be aimed at + ING – the purpose / aim is to + infinitive.

The fibres are carefully oriented in order to = to = so as to reinforce the structure.
The fibres are carefully oriented with a view to ( = with the aim of) reinforcing the structure.
Carefully orienting the fibres is aimed at reinforcing the structure.
The purpose (= the aim) of a careful orientation of the fibres is to reinforce the structure.

• Fibres are often pre-impregnated with resin : it helps to bring the resin and the fibres together.
• The matrix binds the fibres together : stress is transferred from one fibre to another ;
• Stress is transferred from one fibre to another : this produces a consolidated structure.

COMMUNICATION

17 - Explain and develop orally the reasons for using composites. Turn back to paragraphs 4,5,6. Be as precise as possible. You can use phrases expressing advantages (exercise 12) and drawbacks.

(Note a list of suitable phrases for expressing advantages and drawbacks can be found at the end of the  'Students' Toolbox' ( item #22  in  'Contents of the data bank' .)
 

18 - Write a summary of the text in 120 / 150 words

1. Write your first draft.
2. Use linkwords (expressing cause or consequence, probably, in the summary of paragraphs 2 to 6.) Check that you are using passive forms (e.g. do not write :" we use composites" but "composites are used").

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