The best procedure is a corner integral with the structure, with no joints. This provides optimum performance

Opportunity.

554Repair of Vehicle Bodies

Figure 16.25Orientation of fibre reinforcement

(Courtesy of SPSystems)

to other weave patterns; this also means that it does

not drape very well.

Twill

(Courtesy of SPSystems)

Satin weaves are fundamentally twill weaves modified

to produce fewer intersections of warp and

weft. The harness number used in the designation,

typically 4, 5 and 8 is the total number of fibres

crossed and passed under before the fibre repeats

the pattern. A crowsfoot weave is a form of satin

weave with a different stagger in the repeat pattern.

Satin weaves are very flat and have low crimp

which means that they have excellent mechanical

properties and drape well. Because of the pattern

shape one face of the material will have sections of

fibre running open in one direction, giving an

asymmetric imbalance. Care must be taken when

laying up several layers, to ensure the pattern is set

to minimize stress levels.

Basket

Basket weave is fundamentally the same as plain

weave except that two or more warp fibres alternately

interlace with two or more warp fibres. An

arrangement of two wefts crossing two warps is

designated 2X2 basket. The arrangement of fibres

need not be symmetrical. Basket weave is flatter

and through less crimp is stronger than plain

weave. Basket weave is less stable and is best used

with thicker fibres, called high tex, to avoid excessive

crimping.

Leno

One or more weft fibres alternate by passing over

or under two or more warp fibres. This gives the

visual appearance of a diagonal rib. The threads

therefore have less crimp giving higher mechanical

properties than the plain weave. The fabric looks

smoother and drapes better.

Satin

(Courtesy of SPSystems)

(Courtesy of SPSystems)

Table 16.3Properties of fibreglass composites and alternative materials

Impact

strength

Izod Hardness

Tensile Tensile Flexural Flexural Compressive

strength modulus Elongation strength modulus strength ft lb/in Rockwell

Glass fibre Specific notched (except

by weight gravity Density 103psi 106psi % 103psi 106psi 103psi at 73° F where noted) Flammability

Material ASTM test method % D792 lb/in3 D638 D638 D638 D790 D790 D695 D256 D785 UL–94

Glass fibre Polyester SMC (compression) 30.0 1.85 0.066 12.00 1.70 1.0 26.00 1.60 24.00 16.00 Barcol 68 5V

reinforced Polyester SMC (compression) 20.0 1.78 0.064 5.30 1.70 .4 16.00 1.40 23.00 8.20 Barcol 68 5V

thermosets Polyester SMC (compression) 50.0 2.00 0.072 23.00 2.27 1.7 45.00 2.00 32.00 19.40 Barcol 68 5V

Polyester BMC (compression) 22.0 1.82 0.065 6.00 1.75 .5 12.80 1.58 20.00 4.26 Barcol 68 5V

Polyester BMC (injection) 22.0 1.82 0.065 4.86 1.53 .5 12.65 1.44 — 2.89 Barcol 68 VO

Epoxy (filament wound) 80.0 2.08 0.061 80.00 4.00 1.6 100.00 5.00 45.00 45.00 M98 VO

Polyester (pultruded) 55.0 1.69 0.060 30.00 2.50 — 30.00 1.60 30.00 25.00 Barcol 50 VO

Polyurethane, milled fibres 13.0 1.07 0.038 2.80 — 140.0 — 0.037–0.053 — — SD*65–75 VO

(RRIM)

Polyurethane flaked glass 23.0 1.17 0.042 4.41 — 38.9 — 0.15 — 2.10 — VO

(RRIM)

Polyester (spray-up/lay-up) 30.0 1.37 0.049 12.50 1.00 1.3 28.00 0.75 22.00 13.00–15.00 Barcol 50 VO

Polyester, woven roving 50.0 1.64 0.059 37.00 2.25 1.6 46.00 2.25 27.00 33.00 Barcol 50 VO

(lay-up)

Glass fibre Acetal 25.0 1.61 0.058 18.50 1.25 3.0 28.00 1.10 17.00 1.80 M79 HB

reinforced Nylon 6 30.0 1.37 0.049 24.00 1.05 3.0 29.00 1.11 24.00 2.20 R121 HB

thermoplastics Nylon 6/6 30.0 1.48 0.053 23.00 1.20 1.9 35.00 0.80 26.50 2.20 M95 HB

Polycarbonate 10.0 1.26 0.045 12.00 .75 9.0 16.00 0.60 14.00 2.00 M80 V-1

Polypropylene 20.0 1.04 0.037 6.50 .54 3.0 8.30 0.52 25.00 1.10 R103 HB

Polyphenylene sulphide 40.0 1.64 0.059 22.00 2.05 3.0 37.00 1.90 21.00 1.50 R123 V-O/5V

Acrylonitrile butadiene 20.0 1.22 0.044 11.00 .90 2.0 15.50 0.87 14.00 1.20 R107 HB

styrene (ABS)

Polyphenylene oxide (PPO) 20.0 1.21 0.043 14.50 .92 5.0 18.50 0.75 17.60 1.80 R107 HB

Polystyrene acrylonitrile 20.0 1.22 0.044 14.50 1.25 1.8 19.00 1.10 17.50 1.10 R122 HB

(SAN)

Polyester (PBT) 30.0 1.52 0.054 19.00 1.20 4.0 28.00 1.17 18.00 1.80 R118 HB

Polyester (PET) 30.0 1.56 0.056 21.00 1.30 6.6 32.00 1.25 25.00 1.80 R120 HB

(Continued )

Table 16.3(Continued)

Impact

strength

Izod Hardness

Tensile Tensile Flexural Flexural Compressive

strength modulus Elongation strength modulus strength ft lb/in Rockwell

Glass fibre Specific notched (except

by weight gravity Density 103psi 106psi % 103psi 106psi 103psi at 73° F where noted) Flammability

Material ASTM test method % D792 lb/in3 D638 D638 D638 D790 D790 D695 D256 D785 UL-94

Unreinforced Acetal — 1.41 0.051 8.80 .41 40.0 13.00 0.38 16.00 1.00 M78–M80 HB

thermoplastics Nylon 6 — 1.12 0.040 11.80 .38 30.0 15.70 0.39 13.00 0.60 R119 HB

Nylon 6/6 — 1.13 0.041 11.50 .40 60.0 17.00 0.42 15.00 0.80 R120, M83 V-2

Polycarbonate — 1.20 0.043 9.50 .34 110.0 13.50 .34 12.50 16.00 M70 V-2

Polypropylene — .89 0.032 5.00 .10 200.0 5.00 0.13–0.20 3.50 1–20 R50–96 HB

Polyphenylene sulphide — 1.30 0.045 9.50 .48 1.0 14.00 0.55 16.00 0.50 R123 V-O

Acrylonitrile butadiene — 1.03 0.037 6.00 .30 5.0 11.00 0.35–0.40 10.00 3–6 R107–115 HB

styrene (ABS)

Polyphenylene oxide (PPO) — 1.10 0.039 7.80 .38 50.0 12.80 0.33–0.40 12.00 5.00 R115 V-1

Polystyrene acrylonitrile — 1.05 0.038 9.50 .40 .5 14.00 0.55 14.00 0.30–0.45 M80–85 HB

(SAN)

Polyester (PBT) — 1.31 0.047 8.20 .28 50.0 12.00 0.33–0.40 8.60 .80 M68–78 HB

Polyester (PET) — 1.34 0.048 8.50 .40 50.0 14.00 0.35–0.45 11.00 0.25–0.65 M94–101 HB

Metals ASTM A-606 HSLA steel — 7.75 0.280 65.00 30.00 22.0 — — 65.00 — B80 —

(cold rolled)

SAE 1008 low-carbon steel — 7.86 0.280 48.00 30.00 37.0 — — 48.00 — B34–52 —

(cold rolled)

AISI 304 stainless steel — 8.03 0.290 80.00 28.00 40.0 — — 80.00 — B88 —

TA 2036 aluminium (wrought) — 2.74 0.099 49.00 10.20 23.0 — — 49.00 — R80 —

ASTM B85 aluminium — 2.82 0.102 48.00 10.30 2.5 — — 48.00 — Brinell 85 —

(die cast)

ASTM AZ91B magnesium — 1.83 0.066 33.00 65.00 3.0 — — 33.00 — Brinell 85 —

(die cast)

ASTM AG40A zinc — 6.59 0.238 41.00 10.90 10.0 — — 41.00 — Brinell 82 —

(die cast)

*Shore D

Reinforced composite materials 557

Leno weave is used to improve the stability in open

fabrics which have a low fibre count. It is a form of

plain weave in which the adjacent weft fibres are

twisted around consecutive warp fibres. Fabrics in

leno weave are usually used in conjunction with

other weave style fabrics as leno weave alone is

unlikely to produce sufficient strength because of

its openness.

Figure 16.26Bonded joints

Figure 16.27Mercedes Mchaven SLR body-in-white

Figure 16.28Carbon fibre composite front nose of

Mercedes Mchaven SLR

Table 16.4Compatibility of materials and processes for fibreglass composites

Thermosets Thermoplastics

Injection moulding • • • • • • • • • • • • • •

Hand lay-up • •

Spray-up • •

Compression moulding • • • • •

Preform moulding • •

Filament winding • •

Pultrusion • •

Resin transfer moulding • ••

Reinforced reaction injection moulding • • • •

Polyester

Polyester SMC

Polyester BMC

Epoxy

Polyurethane

Acetal

Nylon 6

Nylon 6/6

Polycarbonate

Polypropylene

Polyphenylene sulphide

ABS

Polyphenylene oxide

Polystyrene

Polyester PBT

558Repair of Vehicle Bodies

Table 16.6Properties of reinforcement fibres and other materials (Courtesy of SPSystems)

Material type Tensile strength (MPa) Tensile modulus (GPa) Density (g/cc) Specific modulus

Carbon HS 3500 160–270 1.8 90–150

Carbon IM 5300 270–325 1.8 150–180

Carbon HM 3500 325–440 1.8 180–240

Carbon UHM 2000 440_ 2.0 200_

Aramid LM 3600 60 1.45 40

Aramid HM 3100 120 1.45 80

Aramid UHM 3400 180 1.47 120

Glass – E glass 2400 69 2.5 27

Glass – S2 glass 3450 86 2.5 34

Glass – quartz 3700 69 2.5 31

Aluminium alloy (7020) 400 1069 2.7 26

Titanium 950 110 4.5 24

Mild steel (55 Grade) 450 205 7.8 26

Stainless steel (A5–80) 800 196 7.8 25

HSS steel (17/4 H900) 1241 197 7.8 25

Table 16.5Resin comparison (Courtesy of SPSystems)

Material Advantages Disadvantages

Polyester Easy to use; lowest cost resin Only moderate mechanical properties; high styrene

emissions on open moulds; high cure shrinkage;

limited range of working times

Vinylester Very high chemical/environmental Postcure generally required for high mechanical

resistance; higher mechanical properties properties; high styrene content; double cost of

than polyesters polyester; high cure shrinkage rate

Epoxy High mechanical and thermal properties; Critical in mixing; corrosive; dangerous to

high water resistance; long working times handle; triple cost of polyester

available; temperature resistance up to

220 °C; low cure shrinkage

Mock leno

(Courtesy of SPSystems)

Mock Leno is a version of plain weave in which

the fibres under–over interlace every two or more

fibres apart. This give a thicker fabric which has a

rougher surface texture and very good porosity.

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