T TESTING AND DESIGN (FOURTH CONFERENCE) A conference sponsored by the AMERICAN SOCIETY FOR TESTING AND MATERIALS Valley Forge, Pa, 3-4 May 1976 ASTM SPECIAL TECHNICAL PUBLICATION 617 J G Davis, Jr., conference chairman List price$51.75 04-617000-33 AMERICAN SOCIETY FOR TESTING AND MATERIALS 1916 Race Street, Philadelphia, Pa 19103 # Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized © by AMERICAN SOCIETY FOR TESTING AND MATERIALS 1977 Library of Congress Catalog Card Number: 76-40796 NOTE The Society is not responsible, as a body, for the statements and opinions advanced in this publication Primed in Baltimore, Md March 1977 Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Foreword The Fourth Conference on Composite Materials: Testing and Design was held 3-4 May 1976 at Valley Forge, Pa The American Society for Testing and Materials' Committee D-30 on High Modulus Fibers and Their Composites sponsored the conference J G Davis, Jr., National Aeronautics and Space Administration-Langley Research Center, served as conference chairman Most of the papers presented at the eight sessions are included in this volume which complements the first, second, and third conference publications—>lSrM STP 460, ASTM STP 497, and ASTM STP 546, Composite Materials: Testing and Design Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Related ASTM Publications Composite Reliability, STP 580 (1975), $49.75 (04-580000-33) Fracture Mechanics of Composites, STP 593 (1976), $23.50 (04-593000-33) Environmental Effects on Advanced Composite Materials, STP 602 (1976), $10.00 (04-602000-33) Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized A Note of Appreciation to Reviewers This publication is made possible by the authors and, also, the unheralded efforts of the reviewers This body of technical experts whose dedication, sacrifice of time and effort, and collective wisdom in reviewing the papers must be acknowledged The quality level of ASTM publications in a direct function of their respected opinions On behalf of ASTM we acknowledge their contribution with appreciation ASTM Committee on Publications Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Editorial Staff Jane B Wheeler, Managing Editor Helen M Hoersch, Associate Editor Ellen J McGlinchey, Assistant Editor Kathleen P Turner, Assistant Editor Sheila G Pulver, Assistant Editor Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Contents Introduction FRACTURE AND FATIGUE Fracture Resistance Characterization of Graphite/Epoxy Composites— D H MORRIS AND H T HAHN Experimental Program Results Conclusions 15 An Experimental Study of tlie Fracture Behavior of Laminated Graphite/Epoxy Composites—H F BRINSON AND Y T YEOW Materials and Test Procedures Experimental Results Discussion 18 22 22 34 Effect of Time at Load on Fatigue Response of [(0/±45/90) J ^ T300/5208 Graphite-Epoxy Laminate—G P SENDECKYJ AND H D STALNAKER 39 Experimental Results Analysis of Test Results Conclusions 40 46 51 Preliminary Development of a Fundamental Analysis Model for Crack Growth in a Fiber Reinforced Composite Material— M F KANNINEN, E F RYBICKI, AND W I GRIFFITH 53 Analysis Procedure Example Computational Results and Discussion 54 62 Fatigue of Notched Fiber Composite Laminates: Analytical and Experimental Evaluation—S V KULKARNI, P V MCLAUGHLIN, J R , R B PIPES, AND B W ROSEN 70 Static Failure Model Fatigue Analysis Experimental Program Analysis/Experiment Correlation Study Concluding Remarks 72 75 78 84 91 Copyright by Downloaded/printed University of ASTM Int'l (all by Washington (University rights reserved); of Washington) Sun pursuant Jan to License Delamination in Quasi-Isotropic Graphite-Epoxy Laminates— K L REIFSNIDER, E G HENNEKE II, AND W W STINCHCOMB 93 Experimental Program Results Discussion and Conclusions 94 96 103 Structural Design Significance of Tension-Tension Fatigue Data on Composites—G C GRIMES 106 Graphite/Epoxy Fatigue 107 Hybrid Composites 113 Structural Design Significance 116 Conclusions 119 MATERIALS AND PROCESSING Evaluation of Selected High-Temperature Thermoplastic Polymers for Advanced Composite and Adhesive Applications— M G MAXIMOVICH 123 Resin Selection and Characterization Graphite/300P Development Graphite/PPQ 401 Development Graphite Scrim/PPQ Adhesive Bonds Discussion Conclusions 124 125 128 132 134 135 Development of Multidirectional Fiber-Reinforced Plastics— Y SUEZAWA, M TAKEMOTO, ANDS TAKAHASHI 137 Fabrication Method of Multidirectional Glass-Fiber Reinforced Plastics (M-D GFRP) Mechanical Properties of M-D GFRP Fracture Mode of M-D GFRP Improvement of the Strength of M-D GFRP Conclusions 137 139 143 144 150 TEST METHODS Acoustic Emission Response Characteristics of Metal Matrix Composites—R B PIPES, N J BALLINTYN, W R SCOTT, AND J M CARLYLE 153 Specimen Design and Fabrication Experimental Facilities and Procedures Mechanical Property Results Composite Resuhs Acoustic Emission Response Analysis and Conclusions Copyright by Downloaded/printed University of ASTM Int'l (all by Washington (University rights of 155 156 157 159 160 163 reserved); Washington) Sun Jan pursuant to License 20:09:2 A Compression Testing of Large Gage Lengtii Composite Coupons— J T RYDER AND E D BLACK 170 Compression Testing Procedure Experimental Verification Summary and Conclusions 172 177 188 Nondestructive Tests for Sliear Strength Degradation of a GraphiteEpoxy Composite—D H KAEBLE AND P J DYNES 190 Experimental Results Summary 191 191 199 Failure Analysis of tlie Split-D Test Method—C E KNIGHT, Finite Element Model and Analysis Results of Analysis Experimental Results Conclusions and Recommendations Longitudinal Residual Stresses in Boron Fibers—D R Experimental Test Apparatus Specimen Description Analysis of the Data Experimental Results Discussion 201 202 206 212 214 JR 215 216 218 218 219 222 BEHRENDT DESIGN AND ANALYSIS Effect of Stacking Sequence on the Notched Strength of Laminated Composites—J M WHITNEY AND R Y KIM 229 Experimental Program 230 Data Reduction 234 Discussion and Conclusions 238 An Analysis Model for Spatially Oriented Fiber Composites— B W ROSEN, S N CHATTERJEE, AND J J KIBLER 243 Background Description of the Model Method of Analysis Property Predictions Concluding Remarks 244 246 248 251 253 Empirical Crippling Analysis of Graphite/Epoxy Laminated Plates—E E SPIER AND F L KLOUMAN Experimental Procedure Copyright by Downloaded/printed University of ASTM Int'l (all by Washington (University rights of reserved); Washington) Sun 255 257 Jan pursuant to 20:09:22 License Agreem SHIRRELL AND HALPIN ON MOISTURE ABSORPTION 515 a dilatation of the matrix This results in internal stress changes in the laminate and reduction in the resin softening temperature (that is, glass transition temperature) The magnitude of these changes is sensitive to the amount of absorbed moisture and its distribution in the laminate This paper will review the nature of moisture absorption by epoxy composite laminates, the induced environmental dilatation of the matrix, and, consequently, the dimensional changes of the laminate It also will outline the attendent internal stress changes and examine the corresponding reduction in the resin softening temperature Theory of Diffusion Diffusion is the process by which matter is transported from one part of a system to another as a result of random molecular motion Transfer of heat by conduction is also due to random molecular motion, and there is an obvious analogy between the two phenomena This analogy was first recognized by Fick [1],^ who adopted the mathematical formulism developed by Fourier [2] for heat conduction and appUed it to diffusion The mathematical theory of diffusion is based on the hypothesis that the rate of transfer, F, of diffusion matter through unit area of a section is proportional to the concentration gradient normal to the section, that is -Ddc/dx (1) where c = concentration of diffusing substance, X = space coordinate measured normal to the section, and D = diffusion constant or sometimes called the diffusivity The negative sign in this equation arises because diffusion occurs in the direction opposite that of increasing concentration Equation is known as Fick's first law, and it applies to the equilibrium state obtained during permeabiUty where the concentration gradient dc/dx at any point is constant Fick's second law for one dimensional diffusion reads dc/dt = diDdc)/dx^ (2) This equation describes the nonstationary state before equilibrium is reached, the concentration gradient being a function of the x-coordinate, which is the direction of the movement of the diffusion penetrant By inspection of Eq 2, it is obvious that its sohuion will yield a kinetic rela^The italic numbers in brackets refer to the list of references appended to this paper Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 516 COMPOSITE MATERIALS (FOURTH CONFERENCE) tion between c and t involving D and x When the diffusion constant is independent of concentration, Pick's second law can be solved analytically For a sheet of solid material with a large surface area relative to its thickness and suspended in an atmosphere containing a penetrant, the boundary conditions are c = Co at / = and all x c ~ Co= dX X = and x = / at f > 0, and c = Coo at ? = 00 and all x Equation then gives the following solution [5] c, "v - = 1- - 1)-' sin : (2/1 + T Coo — Co (2n +- iK^i \)TX 1=0 r -D{2n + ly^^t (3) 1—r^v where / = thickness of the sheet; Co, Ci, and Coo = concentrations of penetrant at a point x in the sheet at times 0, t, and oo^ respectively, and, n = integer The total amount of penetrant absorbed by the sheet can be obtained by integration of Eq through the thickness of the sheet, that is m = c{x, t)dx (4) which on substitution becomes m, - nto = "^ /Woo -nto T^ 1=0 E (2n + 1)-' exp -D(2n + Ifw^t (5) where nto, m,, and /Woo are the moisture content at time 0, /, and 0°, respectively Since the series involved in Eq converges rapidly, for times slightly larger than zero, only the first term of the series is of consequence during most of the absorption process [i] Consideration of only this term leads to / X iif^^ (Y y* 1 1 10 TIME(DAYS)^ FIG 3—Temperature accelerates the approach to equilibrium saturation 1.6 p T300/520ei 75°Fi75« RH; Ref [12] ^ • • 1.4 1.2 UJ 1.0 O Ul 8 16 24 Plies Plies Plies Plies —•—;^-=4 ae a ^Mf^ i 1 TIME(DAYS)^ FIG 4—Moisture absorption varies with thickness sion This equation implies that a plot of log D versus \/T should yield a straight line if Eq 11 describes the temperature dependence Figure indicates that this is the case for epoxy-composite laminates Fiber Obstruction The interrelationships between matrix, fiber, and composite diffusivity are available by virtue of a correspondence principle which interrelates transport calculations with shear stiffness calculations [18] Accordingly, the micromechanics known as the Halpin-Tsai equation [19] yield Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized SHIRRELL AND HALPIN ON MOISTURE ABSORPTION 521 20.0 BR/5505116 ply laminate 100%RH;Ref.[1Tj FIG S—Diffusivity as a function of temperature for moisture absorption Du^X/Df + \rr,Dm (12) for diffusion parallel to the fiber direction, and D22 D}i + fr,X/ Dm Dn - rjXf (13) where r, = {Df/Dn, - l)/{Df/D„ + n r =1 for diffusion perpendicular to the fiber axis or the plane of a plate, Df and D„ are the diffusivities of the fiber and matrix, respectively For the vast majority of engineering systems, Df/D„ and Dm > Dn > D22 or As because the fibers act to obstruct diffusion paths perpendicular to their axis or cross section [10] Accordingly, studies indicating that Du >D22 or D33 not necessarily mean that the fiber-matrix interface is a preferential conductive path for water Other authors [14] have shown a positive correlation between thermal transport and diffusion calculations Moisture Concentration The diffusion of moisture into many polymers differs from that of other penetrants in that it is concentration dependent This is generally believed to be caused by swelling of the polymer matrix by the water molecules, leading to a loosening of the polymer structure which facilitates the movement of the diffusing molecules [10] The mathematical and Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 522 COMPOSITE MATERIALS (FOURTH CONFERENCE) experimental approach to concentration-dependent diffusion offers considerable difficulties Crank and co-workers [5-7], in particular, have developed the mathematical treatment for concentration-dependent diffusion coefficients and methods for their experimental determination To date, there has been no attempt to determine the relationship between concentration and diffusivity in epoxy composite laminates Swelling In deriving Eqs and 5, it is assumed that the dimensions of the laminate remain constant However, for situations where the laminate swells, these equations can still be used provided a frame of reference is taken with respect to the moisture in the laminate, von Amerongen [70] describes in detail two methods which can be used to approach this problem Effects of Moisture Absorption Induced Environmental Dilatation in the Resin Equation of the preceding section'states that the mass of HjO absorbed must add to the mass of the resin or matrix material If the assumption of the additivity of volumes is made, then laminate + KH,O = swollen volume (14) and the induced dilatational may be estimated as AV{t) = Pr/n, KH.O Vo (15) where FH^O is the specific volume of water Within the restriction that the moisture distribution is uniform and that the material is isotropic, the dilatational strains will be AV ei = 62 = ei = —-rJ (16) yo or using Eq 15 em = ~ prm, VHJO (17) The correlation of the induced dimensional changes with moisture content for a bulk resin is shown in Fig Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized SHIRRELL AND HALPIN ON MOISTURE ABSORPTION 4.0 523 NEAT RESIN CASTINGS OF: • -WHITTAKER SR-10S00, •-FIBERITE934 ) #^ Ref.l20| 3.0 - • - HERCULES 0 V-ERLB4617/MP0A \ A - FERRO E-2g3 • -HERCULES - i R e f l l l | P 2.0 1.0 MOISTURECONTENT.wt^ FIG 6—Swelling behavior is similar for several epoxies Environmentally Induced Dimensional Changes in Laminates The attendent consequence from Eq 17 is that laminates in which resin matrixes are a constituent part must experience dimensional changes as they absorb moisture The theoretical basis for relating the dilatation of the resin to the dimensional changes in the laminate has been developed by Halpin and Pagano [21\ in 1968 and verified by Halpin [22] and Fahmy and Ragai [23] The pertinent results for the in-plane strains included in a lamina are Emem^m ei = + Efef\f (18) Em Am + Ef \f and ^2 = (1 + Vm)em Xm + (1 + V/)e/\/ - e\(vf\f + Vm\m) (19) where e™ is obtained from Eq 17 The subscripts and in Eqs 18 and 19 refer to the longitudinal fiber direction and the matrix direction Employing these results for a single unrestrained layer and laminated plate theory, the following results were obtained for the in-plane expansion strains A22R1 — AnRi e\ = An All - An^ AuRi — AtiRi ei = An All - (20) Aii^ where Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 524 COMPOSITE MATERIALS (FOURTH CONFERENCE) Ri = Jih + JiHx, R2 = Jih - JiHx An = Uih + U2H1 + U3H2, A22 = U,h - U2H1 + UiHi An = U,h - U3H2 / , = (C/i + U,)Wi m = (ei + 62)72, + 2U2W2, J2 = U2W1 + 2Wt(Ui + 2Ui - t/4) W2 = (ei - e2)/2 Hi = J^ hu coslQu u=0 u=N H2 = u^= hu cosABu C/i = 1/2 (3 Qu + 3Q22 + 2(2,2 + 4Q66), U, = 1/8(Q„ + Q22 - 2Qn - AQ^), Qn = £11/(1 Q12 = — I'121'2l), i'i2 Q22 = ^21 Q i i , f/2 = 1/2 (Qn - Q22) U, = 1/8(Q„ + ^22 + 6Qn - AQ^) Q22 = £ 2 / ( — I'12I'2l) Qi(, = Gn and where h is the thickness of the laminate When these calculations are employed to evaluate the expected in-plane dimensional changes induced by moisture absorption for reaUstic laminates (that is, O2 ± 45), relative small strains are observed in comparison to the rather large observed strains for the resin (Fig 6) This result is due to the restraint that the high-modulus fibers exert on the in-plane deformations However, the matrix does swell with moisture absorption, and, if it cannot expand in the laminative plane, it will expand transverse to the laminative plane This thickness expansion will be large since the high-modulus fibers cannot control the thickness direction Pagano [24] and Fahmy and Ragai [25] have developed the appropriate expressions The dimensional change in the thickness of an unconstrained, isolated ply is ei = 62 For a constrained ply or lamina within a laminate, the out-of-plane strain is (l'13 + Ci = l'12I'23)(ei - e\) + (l'23 -I- l ' I ' l ) ( e - €2) 1'12 1'2I (21) Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized SHIRRELL AND HALPIN ON MOISTURE ABSORPTION 525 e^^^ei - vi}(ei - e\) - viiiei - ei) The expression for the expansional strain, 63, through the laminate thickness direction for a symmetrical angle-ply laminate of equal thickness plies is (Ii cos^le + I2 sin226/)(e3 - €2) = h sin^lQ (22) where Ii = EwEii 12 = GMIEU + (1 + 2vn)E2i] 13 = EwGuiei - e\)(v2iv\2) The corresponding approximates of Fahmy and Ragai are ^3^62 - Vn(e\ - e\) - U23(e2 - 62) (23) These results may be extended to more complex lamination patterns, within the Umitations of balanced and symmetrical angle plies ±0, by a summation through the thickness direction k=N eu = Y, e{± 9k)a'' k=l (24) with a* = A/zV/i where A/i* is the total thickness of the specific ± Bk angle-ply system and h is the total laminate thickness of flayers These results were employed in a series of computations which are illustrated as follows m,(comp) = 0.01 (or percent based upon laminate absorption) Utilizing Eqs 10 and 17 the induced linear expansional strain in the resin is em = 0.0194 (for/M, (resin) ^ percent) from Eqs 18 and 19 the induced lamina strains are ei = 0.00, ei = ei = 0.00786 and from Eqs 20 and 22 the induced laminate strains are Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 526 COMPOSITE MATERIALS (FOURTH CONFERENCE) [02/ + 45].ei = 0.0015, ^2 = 0.00242, gj = 0.00734 The correlation between the out-of-plane laminate expansion e^ and experimental data are illustrated in Fig THICKNESS DIRECTION [ , / * 45] LAMINATES T300/6208 002 006 010 014 SWELL, in/in FIG 7—Moisture induced laminate dimension change (data from Ref 26) Consequences of Environmentally Induced Dilatation The induced dilatation in the presence of a moisture gradiant can produce significant induced internal stresses and a change in the apparent glass transition temperature of the resin For engineering applications, the induced stress concentration will be at the edges of the structure or of condition elements On exposure to a humidity environment, the edges will absorb rapidly until equilibrium is established and a diffusion gradiant is created in the laminate The areas absorbing moisture will expand out of plane in accordance with Eqs 21 and 22 This swelling will be resisted by the unswoUen portion of the laminate inducing a compression stress at the outer edge reacted by an induced tensile stress at a distance into the laminate When the laminate is subject to a desorption condition, the outer edges will lose their moisture first Since this effect will be rapid with respect to the internal diffusion of the moisture to an outer surface, the shrinkage of the edge will induce a tensile stress on the edge If the swelling strains are large, these induced stresses can initiate edge crack growth The important point, here, is that when an accelerated conditioning environment is selected for environmental testing of composite laminates, one should look to limit the edge swelling by not employing excessively high relative humidities approaching 100 percent but rather accelerate difCopyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized SHIRRELL AND HALPIN ON MOISTURE ABSORPTION 527 fusion by employing increased temperatures This approach will not only limit the edge stresses but will spread out the internal moisture gradiants, thereby, producing a more favorable internal stress distribution Another consequence of the absorption of moisture and the corresponding volumetric dilatation of the resin is a reduction in the glass transition temperature of the resin matrix This effect is well known in the physics of polymers [27] and can be correlated easily with the analytical expressions developed by Kelley and Buecke [28] Current expectations are that aircraft structures containing epoxy materials will typically see about percent moisture weight gain in the matrix phases Current approaches to processing of commercial prepregs yield Tg's of the resin between 375 to 400°F For such a material the induced moisture will reduce the in-service glass transition temperature to below 300 °F While such a state will provide a useful engineering material, the design margins are smaller than hoped for This effect has placed additional pressure on the engineering data development during the design verification and qualification procedures Summary During the past decade boron and graphite fiber reinforced composites have evolved from a laboratory curiosity to a practical engineering material However, concern over their environmental durability is limiting their potential applications in numerous areas In part, this concern has been created by the lack of environmental data establishing the reliability of epoxy composites in resisting the degradatory effects of atmospheric exposure The incompleteness of these data make it impossible to make detailed quantitative statements about the nature of the environmental durability of epoxy composites However, from what limited data are available, it is possible to state some general observations: The rate of moisture absorption by epoxy composites is governed by a diffusion mechanism Moisture absorption produces predictable dimensional changes in both neat resin and laminates Moisture absorption by epoxy composites can result in the formation of concentration gradiants through the laminate These concentration gradients could cause unequal swelling stresses and result in the formation of microcracks Dilatation of the resin by the absorbed moisture leads to a reduction in the elevated-temperature resin dependent mechanical properties of the laminate due to a reduction in the glass transition temperature of the resin Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 528 COMPOSITE MATERIALS (FOURTH CONFERENCE) Numerous studies are in progress which will provide the necessary data to resolve the degree of degradation in mechanical properties induced by environmental exposure References [/] Fick, A., Annalen Der Physik, Vol 170, 1855, p 59 [2] Fourier, J B., Theorie Analytique de la Chaleur, Euvres de Fourier, 1822 [3] Crank, J., The Mathematics of Diffusion, Oxford University Press, London, England, 1956 [4] Long, F A and Bagley, E., Journal of the American Chemical Society, Vol 77, 1955, p 2172 [5] Crank, J and Henry, M E., Transactions of the Faraday Society, Vol 45, 1949, pp 636-650 [6] Crank, J., Transactions of the Faraday Society, Vol 51, 1955, pp 1632-1641 [7] Hartley, G S and Crank, J., Transactions of the Faraday Society, Vol 51, 1955, pp 1632-1641 [S] Barrier, R M and Brook, D W., Transactions of the Faraday Society, Vol 49, 1953, pp 1049 [9] von Wroblewski, S., Annalen der Physic und Chemie, Vol 8, 1879, p 29 [10] von Amerongen, G T., Rubber Chemistry Technology, Vol 37, 1964, pp 1065-1152 [11] Browning, C E., private communication [12] McKague, E L., Reynolds, J D., and Halkias, J E., "Life Assurance of Composite Structures," Vol 1, Technical Report AFML-TR-75-51, Air Force Materials Laboratory, Dayton, Ohio, 1975 [13] Moore, W J., Physical Chemistry, Prentice Hall, Englewood, N J., 1962, p 126 [14] Shen, Chi-Hung and Springer, G S., Journal of Composite Materials, Vol 10, 1976, pp 36-54 [75] Eyring, H., Journal of Chemical Physics, Vol 4, 1934, p 283 [16\ Barrier, R M., Nature, Vol 140, 1937, p 106 [17] Carpenter, J F., "Moisture Sensitivity of Epoxy Composites and Structural Adhesives," McDonnell Aircraft Company Report A2640, McDonnell Aircraft Company, St Louis, Mo., Dec 1973 [18] Ashton, J E., Halpin, J C , and Petit, P H., Primer on Composite Materials: Analysis, Technomic Publishing Co., Stamford, Conn., 1969 [79] Halpin, J C and Kardos, J L., Polymer Engineering and Science, Vol 16, p 344, 1976 [20] Hertz, J., "Investigation into the High Temperature Strength Degradation of FiberReinforced Resin Composite During Ambient Aging," Technical Report NAS8-27435, National Aeronautics and Space Administration, Huntsville, Ala., 1973 [27] Halpin, J C and Pagano, N J., in Recent Advances in Engineering Science, A C Eringen, Ed., Gorden and Breach, London, England, 1970, p 33 [22] Halpin, J C , Journal of Composite Materials, Vol 3, 1969, p 732; Halpin, J C and Pagano, N J., Journal of Composite Materials, Vol 3, 1969, p 720 [23] Fahmy, A A and Ragai, A N., Journal of Applied Physics, Vol 41, 1970, p 5112 [24] Pagano, N J., Journal of Composite Materials, Vol 8, 1974, p 310 [25] Fahmy, A A and Ragai, A N., Journal of Composite Materials, Vol 8, 1974, p 90 [26] McKague, E L., private communication [27] Buecke, F., Physical Properties of Polymers, Interscience, New York, 1962, p 112 [28] Kelley, F N and Buecke, F., Journal of Polymer Science, Vol I, 1961, p 549 Copyright by ASTM Int'l (all rights reserved); Sun Jan 20:09:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized