Tensile measurement of neat resin properties Em and Sm1. (+). ASTM D 638-03
Type I, II, III, IV and V neat resin tensile specimen geometries. (From ASTM ...
Mechanical Testing of Composites and their Constituents • Tests done to determine intrinsic material properties such as modulus and strength for use in design and analysis (major emphasis here) • Tests done to determine quality or acceptability of specific components during manufacturing (minor emphasis here)
American Society for Testing and Materials (ASTM) Standards • Test standards for polymer matrix and metal matrix composites - ASTM Vol. 15.03 Space Simulation; Aerospace and Aircraft; Composite Materials • Test standards for ceramic matrix composites – ASTM Vol. 15.01 – Refractories; Activated Carbon; Advanced Ceramics
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Direct measurement of fiber longitudinal properties Ef1 and SL(+)
Different ways of mounting fiber specimens on backing strip. (From ASTM Standard C 1557-03ε1 )
Indirect measurement of fiber longitudinal properties Ef1 and SL(+)
Note: strength and modulus values must be corrected to account for the portion of the load carried by resin (use micromechanics equations)
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Different failure modes for resin-impregnated strand test specimens. (From ASTM Standard D 4018-99)
Indirect measurement of fiber transverse modulus Ef2 P = load
P Prediction Experimental data
∆ ∆ = deflection
Note: Experimental load-deflection curve compared with predicted curve (from finite element model) using Ef2 as a curve-fitting parameter in prediction (From Kawabata, 1989)
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Torsional pendulum for measuring longitudinal shear modulus of fiber, Gf12. (From Tsai and Daniel, 1999)
Tensile measurement of neat resin properties Em and Sm1(+)
ASTM D 638-03 Type I, II, III, IV and V neat resin tensile specimen geometries. (From ASTM Standard D 638-03
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ASTM 618-05 Conditioning Plastics and Electrical Insulating Materials for Testing
Standard Laboratory Atmosphere: Temperature of 23C (73.4F) and relative humidity of 50%
Specimen for measurement of neat resin compressive properties Em and Sm1(-)
Neat resin compressive test specimen (From ASTM Standard D695-02a)
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Neat resin compression specimen support jig
(From ASTM Standard D695-02a)
Compression test fixture for neat resin specimen
(From ASTM Standard D695-02a)
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3 point bending specimen for measurement of flexural properties of neat resin or composite (From ASTM Standard D790-03)
M Bending moment diagram
4 point bending specimen for measurement of flexural properties of neat resin or composite (From ASTM Standard D790-03)
M
Bending moment diagram
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Constituent Volume Fraction Measurement • Removal of resin matrix from composite sample by either chemical digestion with acids or other chemicals (carbon fiber composites), or resin burn-off in a furnace (glass fiber composites) according to ASTM Standard D3171-99 • Computer-aided image analysis of digital photomicrographs to determine fiber area fractions of polished composite specimens
Composite tensile specimen for measurement of longitudinal properties E1 and SL(+) Tab Bevel Angle
Overall Length
Tab Thickness
Specimen Thickness Width
Tab Length
Specimen geometry from ASTM D 3039/D 3039M-00ε2
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Typical stress-strain curves from D3039 specimen
(From Carlsson and Pipes, 1989)
End constraints can cause bending of off-axis tensile specimens due to shear coupling
(From Pagano and Halpin, 1968)
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Importance of specimen length-to-width ratio
σ y =τ xy = 0 σ x = Exε x
ε y = γ xy = 0 σ x =Q εx 11
Ex ≠ Q !!!!! 11
Difference between Ex and Q for graphite/epoxy 11
Ex
Q ≈10Ex !!!!! 11
“Modulus”
O0
450
900
Fiber orientation, θ
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Lamina tensile strength can be “backed out” from laminate tensile test data
From Rawlinson, 1991
Compression test specimen for ASTM D3410/D3410M-03
Note: D3410 fixtures produce side-loading rather than end-loading as in D695
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Cutaway view of compression test fixture for ASTM D3410/D3410M-03
Sandwich beam specimen for face sheet compression. (from ASTM Standard D 5467/D 5467M-97)
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Test fixture for ASTM D 6641/D 6641M- 01ε1 combined loading compression (CLC) test method
Test fixture for compressive residual strength of polymer composite plates. (From ASTM D 7137/D 7137M-05ε1
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Comparison of shear test methods for composites. (From Adams, 2005)
Iosipescu test fixture for shear strength and stiffness in all three shear stress states (ASTM D5379)
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Test fixture for V-notched rail shear test. (From ASTM Standard D 7078/D 7078M-05)
Different test specimen arrangements for V-notched rail shear test. (From ASTM Standard D 7078/D 7078M-05
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Rail shear test fixtures, ASTM D4255/D4255M-01 (Methods A and B)
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± 450 Laminate test for in-plane shear modulus G12
σx Shear stress from applied stress: τ12 = 2
Shear strain from measured normal strains: γ12 = ε xo − ε oy τ
Shear modulus: G12 = γ12
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Off-axis tensile test for indirect measurement of G12 Young’s modulus, Ex
∴ Ex =
y
σx
σx εx
When σ x ≠ 0, σ y = τ xy = 0
2
x
Ex =
1
or Ex =
σx 1 = S 11σ x S 11
(2.38)
1 1 4 2v12 1 2 2 1 4 c + − + c s + E s E1 E G 1 12 2
(2.39)
Off-axis tensile test for indirect measurement of G12 • Conduct off-axis tensile test to measure Ex at some fiber orientation θ • Conduct longitudinal tension test to measure E1 and υ12 • Conduct transverse tension test to measure E2 • Use above results in Eq. 2.39 to calculate G12
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ASTM D2344/D2344M-00 Short beam shear test for interlaminar strength (parallel fibers only)
Note: not recommended for measurement of design properties, only for quality control and specification
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Short beam shear test • Short beam fails due to interlaminar shear stress • Long beam fails due to either tensile or compressive normal stress on bottom or top of beam, respectively • Questions about accuracy of mechanics of materials beam theory equations for stresses in short beams where support effects may not be negligible (Whitney’s theory of elasticity analysis)
Exact stress distributions in short beam shear test specimen from theory of elasticity analysis (from J. M. Whitney, Composites Science and Technology, Vol. 22, 1985, pp. 167-184)
Conclusion: Stress distributions from mechanics of materials beam theory are only accurate far away from loads and supports
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Single fiber fragmentation specimen for measurement of fiber/matrix interfacial shear strength
Test procedure: Load specimen until fiber starts to break up into fragments, then measure “critical lengths” of fragments, then calculate interfacial shear strength from theory of discontinuous fiber composites developed later in Chap. 6
Microindenter test for fiber/matrix interfacial shear strength
Test procedure: Load end of fiber in compression with microindenter probe until fiber slips with respect to matrix, then use finite element analysis of specimen to estimate fiber/matrix interfacial shear strength
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Microbond test for fiber/matrix interfacial shear strength
resin droplet
fiber embedded in resin droplet applied tensile force
Problem: Difficult to reproduce the composite resin matrix cure condition in a small droplet.
(From McDonough, et al., 1991)
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Exploded view of test fixture for ASTM D2290 Split Disk Test for Rings
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