Mechanical Testing of Composites

Mechanical Testing of Composites

© 2003, P. Joyce

Tests Accepted by Mil-Hdbk-17 Test Category

Source of Test Method ASTM

SACMA

D2539, C613 D5300

RM 23, RM 24

Volatiles content

D3530

--

Resin flow

D3531

RM 22

Resin gel time

D3532

RM 19

Fiber areal weight

D3776

RM 23, RM 24

Moisture content

D4019

--

Tack

--

--

HPLC

--

RM 20

E1252, E168

--

D4065, D4473

RM 19

E1356

RM 25

Prepreg tests Resin content

IR DMA (RDS) DSC

© 2003, P. Joyce



SACMA

D5229

RM 11

Fiber volume

D3171, D2734

RM 10

Resin content

D3171, D2734

RM 10

Void content

D2584

--

D792, D1505

--

--

RM 10

D4065

RM 18

--

RM 18

E831

--

D696, E228

--

Equilibrium moisture content

D5229

RM 11

Moisture diffusivity

D5229

--

Thermal diffusivity

E1461 © 2003, P. Joyce E1269

--

Lamina physical tests Moisture conditioning

Density Cured ply thickness Glass transition temperature (dry) Glass transition temperature (wet) CTE, out-of-plane CTE, in-plane

Specific heat

--



SACMA

0°/Warp tension

D3039

RM 4, RM 9

90°/Fill tension

D3039, D5450

RM 4, RM 9

0°/Warp compression

D3410, D5467

RM 1, RM 6

90°/Fill compression

D3410, D5449

RM 1, RM 6

D3518, D5448, D5379

RM 7

Interlaminar shear

D5379

--

Short beam shear

D2344

RM 8

--

--

draft

RM 5

Lamina/Laminate Mechanical Tests

In-plane shear

Flexure Open-Hole Compression

© 2003, P. Joyce



SACMA

Open-Hole Tension

D5766

RM 5

Single shear bearing

draft

--

Double-shear bearing

draft

--

Compression after impact

draft

M2

Mode I fracture toughness

D5528

--

Mode II fracture toughness

draft

--

D3479

--

--

--

Lamina/Laminate Mechanical Tests (cont.)

Tension/tension fatigue Tension/compression fatigue

© 2003, P. Joyce

Laminate Testing ¾ ASTM D638 Tensile Properties of Plastics – dogbone specimen

© 2003, P. Joyce

Laminate Testing ¾ ASTM D3039 Tensile Properties of PMC Materials ¾ Used for most aerospace composites

© 2003, P. Joyce

Laminate Testing ¾ ASTM D695 Compressive Properties of Rigid Plastics (1942) ¾ Uses an untabbed, dogboned, flat specimen

© 2003, P. Joyce

Laminate Testing ¾ Modified D695 Compression Test Method ¾Uses a straight sided specimen ¾Tabbed for strength (gage length to short to instrument using strain gages) ¾Untabbed for modulus ¾No ASTM standard governing this method ¾Defined in Boeing Specification Support Standard (BSS 7260, 1982) and SACMA Recommended Test Method (SRM 1-88, 1988)

© 2003, P. Joyce

Laminate Testing ¾ Modified ASTM D695 - Mil-Hdbk-17 interprets this technique to be for 0° direction properties of unidirectional coupons, and 0° and 90° properties of fabric coupons only (and then only when unit cell size of weave or braid is small.)

© 2003, P. Joyce

Laminate Testing ¾ ASTM D3410 Compressive Properties of PMC Materials by Shear Loading ¾ Standard for high modulus carbon fiber composites (1980s) ¾ 0.5” gage length for strain gage sometimes buckles. ¾ Tab failure also problematic.

Celanese fixture © 2003, P. Joyce

Laminate Testing ¾ ASTM D3410 Compressive Properties of PMC Materials by Shear Loading ¾ Standard for high modulus carbon fiber composites (1980s) ¾ 0.5” gage length for strain gage sometimes buckles. ¾ Tab failure also problematic.

IITRI fixture © 2003, P. Joyce

Laminate Testing ¾ ASTM D6641 Compressive Properties using CLC Fixture (2001) ¾ Evolved out of WTF ELSS fixture ¾ Uses straight sided, untabbed specimen ¾ Not recommended for unidirectional composites

© 2003, P. Joyce

Laminate Testing ¾ ASTM D2344 Short-Beam Strength of PMC Materials ¾ Low cost QC test ¾ Material screening

© 2003, P. Joyce

Laminate Testing ¾ ASTM D5379 Shear Properties of Composite Materials by the V Notched Beam Method (Iosipescu)

© 2003, P. Joyce

Laminate Testing (Iosipescu method)

© 2003, P. Joyce

Laminate Testing ¾ ASTM D3518 In-plane Shear (IPS) ¾ Uses ±45° laminate to extract shear properties. ¾ Strictly a shear design allowable ¾ Not used for QC

© 2003, P. Joyce

Laminate Testing ¾ ASTM D790 Flexural Properties of Un-Reinforced and Reinforced Plastics

© 2003, P. Joyce

Laminate Testing ¾ASTM D6484 Open Hole Compressive Strength of PMC Laminates (1999) ¾After Boeing Specification Support Standard BSS 7260, also described in SACMA Recommended Method SRM 3-88.

© 2003, P. Joyce

Laminate Testing ¾ASTM D6742 Filled Hole Tensile/Compressive Strength w Ne Laminates (2002) of PMC

© 2003, P. Joyce

Laminate Testing ¾Creep testing ¾Creep is defined as the change in a property over time when subjected to a constant forcing function. ¾Creep should be considered if the end use ¾involves high stress in the matrix dominated direction ¾high temperature ¾or exposure to a harsh chemical environment © 2003, P. Joyce

Laminate Testing ¾Creep is especially important in composites with a thermoplastic matrix, particularly as TsÆTg ¾Creep is expected to be small in thermoset matrix composites, due to cross-linking. ¾Creep testing is not used to provide primary design data, rather designs should be checked for creep deformation. © 2003, P. Joyce

Testing Fabric-Reinforced “Textile” Composites ¾Refer to ASTM D 6856 Standard Guide for . . . ¾Discusses special testing considerations for textile composites.

© 2003, P. Joyce

Adhesives Testing ¾ ASTM D1002 Single Lap Shear is the most common & industry standard test for: ¾ QC in-process inspection to verify mixing, cure, and surface preparation. ¾ Screening for materials selection.

“five finger” Al specimens

© 2003, P. Joyce

Specimens machined from composite laminate

Adhesives Testing ¾ ASTM D3528 Double Lap Shear minimizes peel, results in higher, more consistent shear strength.

Type TypeABspecimen specimen © 2003, P. Joyce

Adhesives Testing ¾ ASTM D3165 Notched Lap Shear ¾ QC for large laminated assemblies (voids) ¾ Compatibility of different resin systems

© 2003, P. Joyce

Adhesives Testing ¾ ASTM D1780 Adhesive Creep ¾ Apply constant load and measure deflection of scribe marks.

© 2003, P. Joyce

Adhesives Testing ¾ ASTM D1876 Tee Peel ¾ Requires two flexible adherends (Al)

© 2003, P. Joyce

Adhesives Testing ¾ ASTM D3167 Floating Roller (Bell) Peel ¾ One rigid, one flexible adherend

© 2003, P. Joyce

Sandwich Testing ¾ ASTM C297 Flatwise Tensile Strength of Sandwich Constructions (used as workmanship verification, unless very reliable NDE being used.)

© 2003, P. Joyce

Sandwich Testing ¾ ASTM C393 “Long Beam” Flexure ¾ 4 point bending produces uniform bending moment in the center section. ¾ Specimen is sized to induce compression failure in upper skin, not core shear. ¾ Also demonstrates that skin to core strength is adequate to achieve designed facesheet compression stress.

Paste Photo Here

© 2003, P. Joyce

Sandwich Testing ¾ ASTM C393 Beam Flexure ¾ Performed in addition to FWT on co-cured sandwich if rigorous structural requirement. ¾ Accounts for any knockdown from wrinkling/dimpling. ¾ Usually yields lower strength & modulus than solid facesheet tension or compression test.

© 2003, P. Joyce

Sandwich Testing ¾ Mil-Std 401B Core Shear ¾ Used to verify core splice performance. ¾ Can also be used to compare different surface preparations. ¾ Standard configuration uses ¾ 0.062” Al facesheets ¾ 8.1 pcf Al core

© 2003, P. Joyce

Sandwich Testing ¾ ASTM D1781 Climbing Drum Peel ¾ Used for characterization of adhesives for Al facesheet construction ¾ Workmanship test

© 2003, P. Joyce

References ¾ ¾ ¾ ¾ ¾ ¾

Course Notes, Test Methods for Composite Materials, Adams, D. (1991) Mil-Hdbk-17 Composite Materials Handbook Mil-Hdbk-23A Structural Sandwich Composites Wyoming Test Fixtures, Product Catalog No. 106 (2000) ASTM Annual Book of Standards (2001) Engineering Mechanics of Composite Materials, Daniel, I.M. and Ishai, O. (1994)

© 2003, P. Joyce