Opportunity.
554 Repair of Vehicle Bodies
Figure 16.25 Orientation 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 16.3 Properties 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 10 3 psi 10 6 psi % 10 3 psi 10 6 psi 10 3 psi at 73° F where noted) Flammability
Material ASTM test method % D792 lb/in 3 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 10 3 psi 10 6 psi % 10 3 psi 10 6 psi 10 3 psi at 73° F where noted) Flammability
Material ASTM test method % D792 lb/in 3 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 16.26 Bonded joints
Figure 16.27 Mercedes Mchaven SLR body-in-white
Figure 16.28 Carbon fibre composite front nose of
Mercedes Mchaven SLR
Table 16.4 Compatibility 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
558 Repair of Vehicle Bodies
Table 16.6 Properties 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 16.5 Resin 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.
