August 2013 

NASA/TM–2013-218028 

A Test for Characterizing Delamination 

Migration in Carbon/Epoxy Tape Laminates 

James G. Ratcliffe 

National Institute of Aerospace, Hampton, Virginia 

Michael W. Czabaj and Thomas K. O’Brien 

Langley Research Center, Hampton, Virginia 
NASA STI Program . . . in Profile

Since its founding, NASA has been dedicated to the 

advancement of aeronautics and space science. The 

NASA scientific and technical information (STI) 

program plays a key part in helping NASA maintain 

this important role. 

The NASA STI program operates under the 

auspices of the Agency Chief Information Officer. 

It collects, organizes, provides for archiving, and 

disseminates NASA’s STI. The NASA STI 

program provides access to the NASA Aeronautics 

and Space Database and its public interface, the 

NASA Technical Report Server, thus providing one 

of the largest collections of aeronautical and space 

science STI in the world. Results are published in 

both non-NASA channels and by NASA in the 

NASA STI Report Series, which includes the 

following report types: 

TECHNICAL PUBLICATION. Reports of 

completed research or a major significant phase 

of research that present the results of NASA 

Programs and include extensive data or 

theoretical analysis. Includes compilations of 

significant scientific and technical data and 

information deemed to be of continuing 

reference value. NASA counterpart of peerreviewed formal professional papers, but 

having less stringent limitations on manuscript 

length and extent of graphic presentations. 

TECHNICAL MEMORANDUM. Scientific 

and technical findings that are preliminary or of 

specialized interest, e.g., quick release reports, 

working papers, and bibliographies that contain 

minimal annotation. Does not contain extensive 

analysis. 

CONTRACTOR REPORT. Scientific and 

technical findings by NASA-sponsored 

contractors and grantees. 

CONFERENCE PUBLICATION. 

Collected papers from scientific and 

technical conferences, symposia, seminars, 

or other meetings sponsored or cosponsored by NASA. 

SPECIAL PUBLICATION. Scientific, 

technical, or historical information from 

NASA programs, projects, and missions, 

often concerned with subjects having 

substantial public interest. 

TECHNICAL TRANSLATION.

English-language translations of foreign 

scientific and technical material pertinent to 

NASA’s mission. 

Specialized services also include organizing 

and publishing research results, distributing 

specialized research announcements and feeds, 

providing information desk and personal search 

support, and enabling data exchange services. 

For more information about the NASA STI 

program, see the following: 

Access the NASA STI program home page 

at http://www.sti.nasa.gov

E-mail your question to help@sti.nasa.gov

Fax your question to the NASA STI 

Information Desk at 443-757-5803 

Phone the NASA STI Information Desk at 

443-757-5802 

Write to: 

 STI Information Desk 

 NASA Center for AeroSpace Information 

 7115 Standard Drive 

 Hanover, MD 21076-1320
National Aeronautics and 

Space Administration 

Langley Research Center 

Hampton, Virginia 23681-2199 

August 2013 

NASA/TM–2013-218028 

A Test for Characterizing Delamination 

Migration in Carbon/Epoxy Tape Laminates 

James G. Ratcliffe 

National Institute of Aerospace, Hampton, Virginia 

Michael W. Czabaj and Thomas K. O’Brien 

Langley Research Center, Hampton, Virginia 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

Trade names and trademarks are used in this report for identification only. Their usage does not constitute 

an official endorsement, either expressed or implied, by the National Aeronautics and Space 

Administration. 
1

Abstract

A new test method is presented for the purpose of investigating migration of a delamination 

between neighboring ply interfaces in fiber-reinforced, polymer matrix tape laminates. The test 

is a single cantilever beam configuration consisting of a cross-ply laminate with a 

polytetrafluoroethylene insert implanted at the mid-plane and spanning part way along the 

length of the specimen. The insert is located between a 0-degree ply (specimen length 

direction) and a stack of four 90-degree plies (specimen width direction). The specimen is 

clamped at both ends onto a rigid baseplate and is loaded on its upper surface via a piano 

hinge. Tests were conducted with the load-application point located on the intact portion of the 

specimen in order to initiate delamination growth onset followed by migration of the 

delamination to a neighboring 90/0 ply interface by kinking through the 90-degree ply stack. 

Varying this position was found to affect the distance relative to the load-application point at 

which migration initiated. In each specimen, migration initiated by a gradual transition of the 

delamination at the 0/90 interface into the 90-degree ply stack. In contrast, transition of the 

kinked crack into the 90/0 interface was sudden. Fractography of the specimens indicated that 

delamination prior to migration was generally mixed mode-I/II. Inspection of the kink surface 

revealed mode-I fracture. In general, use of this test allows for the observation of the growth of 

a delamination followed by migration of the delamination to another ply interface, and should 

thus provide a means for validating analyses aimed at simulating migration. 

Introduction

Since their introduction as material systems in aerospace vehicles, fiber-reinforced polymer 

matrix composite tape laminates are known to suffer from life-limiting delamination [1]. This 

tendency to form delaminations and the difficulty in detecting such damage, has historically 

limited the use of these material systems in safety critical (primary) structure [2]. In an attempt 

to reverse this scenario, delamination has received considerable attention in the research 

community. In particular, a significant amount of attention has been paid to characterizing the 

three modes of delamination (including delamination under mixed mode loading), which has 

resulted in testing methods for evaluating fracture toughness and fatigue behavior associated 

with these delamination modes [3-11]. 

Delamination simulation is currently being included in commercial finite element analysis 

(FEA) codes based on either a virtual crack closure technique [12, 13] or a cohesive zone 

model [14-17]. These analyses are driven by fracture parameters measured using 

characterization tests. While this overall approach significantly enhances the capability of 

simulating delamination growth, the vast majority of research has focused on delamination 

confined to a single ply interface. In reality, damage in composite laminates often involves 

delaminations that migrate between different ply interfaces. Two such examples that are well 

documented in the literature include, 1) the classic spiral stair case configuration of 

delaminations formed after an impact event that arises due to migration of delaminations 

through several ply interfaces [18-19] and 2) debonding between the flange and skin of 

integrally stiffened panels that has been shown to involve significant delamination migration [20-

21]. These examples highlight that knowledge of delamination growth alone is insufficient for 

being able to simulate some of the key progressive damage mechanisms that potentially limit 

the use of composite laminates in aerospace structure. Furthermore, work has shown that 

simulation of damage formation (including delamination migration) in relatively simple element 
2

specimens such as open-hole tension specimens is difficult to achieve with currently established 

analysis tools [22]. 

Partly in recognition of these difficulties, recent work has focused on developing fracture 

tools for use in commercial FEA codes [23-24], which build upon a numerical framework that 

enables simulation of fracture whose path is not necessarily confined to element boundaries 

[25]. While these newly developed tools, known generically as extended (X-FEM) and 

augmented finite element methods (A-FEM), permit the simulation of events such as 

delamination migration, precise criteria for establishing the occurrence of this process are not 

well understood. Analytical methods based on energy considerations have been developed for 

predicting the kinking of interface cracks (a process directly analogous to migration, which 

involves an interface crack turning and propagating into one of the interfacing materials) for 

isotropic [26] and orthotropic [27] materials. However, these kinking criteria to date have not 

been commonly applied to delamination migration problems. 

Although previous tests have been able to clearly document delamination migration, they 

may not be ideally suited for pinpointing the precise conditions under which delamination 

migration initiates, due either to multiple damage events taking place [20] or the relatively 

complex test configuration [28]. Consequently, it follows that these tests may not be ideal 

means of evaluating kinking criteria for methods such as X-FEM. 

The objective of this work was to directly address the issue stated above and to develop a 

testing method that focuses on the delamination migration process. To this end, clamped beam 

specimen comprised of a IM7/8552 graphite cross-ply tape laminate was designed. The 

specimen, illustrated in Figure 1, contains a polytetrafluoroethylene (PTFE) insert implanted at 

the mid-plane and spanning part way along the length of the specimen. Specimens are loaded 

in such a manner as to result in delamination growth onset followed by migration of the 

delamination to another ply interface. The use of a cross-ply laminate allows an approximately 

two-dimensional characterization of a single migration event. This provides an opportunity to 

evaluate analytical methods aimed at simulating migration and may help identify appropriate 

kinking criteria. This test also offers the opportunity for distinguishing between the migration 

behavior of various composite material systems. 

The remainder of this paper details the design of the delamination migration specimen, 

describes the tests conducted and concludes with a presentation of the test results with 

accompanying discussion. 

Delamination Migration Tests 

 Specimen and Test Fixture 

Specimen Configuration 

A new test method was developed that is based upon the clamped beam configuration 

illustrated in Figure 1. The specimen design possesses three main features that permit the 

controlled observation of delamination growth followed by a single migration event to another 

ply interface. First, the specimen geometry is in the form of a beam with the intent of promoting 

uniform delamination growth and migration across the specimen width. Second, the specimen 

contains a PTFE insert (acting as an artificial delamination) at an interface between a 0-degree 

ply (specimen span direction) and a stack of four 90-degree plies (specimen width direction). 

The 0-degree ply acts to confine the delamination to this 0/90 interface by preventing the 

delamination from migrating through this ply. The 90-degree ply stack provides a path for the 

delamination to kink in to, leading to eventual migration. Third, the specimen can be loaded in a 

manner to cause delamination growth from the PTFE insert that eventually migrates to another 
3

ply interface. This sequence of fracture events (illustrated in Figure 2) is made possible by the 

way in which specimen loading affects shear stresses acting across the delamination front, in a 

manner described previously by Greenhalgh et al [29] (details of this process given in section 

entitled Specimen Load Introduction).

The following three sections contain a detailed description of the steps taken in designing 

the specimen. 

Stacking Sequence and Specimen Dimensions 

The first step to design the specimen was to identify a stacking sequence that allows for 

migration of the delamination to another ply interface. A cross-ply stacking sequence was 

selected in order to promote migration uniformly across the specimen width. As shown in 

Figure 1, the specimen consists of three regions corresponding to the two sublaminates in the 

delaminated portion of the specimen and the intact portion of the specimen. The three regions 

of the specimen are labeled in Figure 1 using numbers such as -.

The specimen is cut from a 44-ply laminate that is a slight modification to a symmetric 

laminate as shown in Figure 3. The nominal total thickness of the 44-ply specimens is 5.25mm, 

corresponding to a 0.12mm ply thickness. One of the 0-degree plies in this stacking 

sequence was relocated to interface with the PTFE insert as illustrated in Figure 3. This 0/90 

ply interface will be the first to delaminate during a test. The lower zero-degree ply essentially 

prevents migration of the delamination created by the PTFE insert downwards into the 

baseplate side of the specimen. A second 0-degree ply was also relocated as illustrated in 

Figure 3 in order to help minimize the asymmetry of the lower arm portion of the specimen. 

A laminated plate theory analysis [30] was performed in order to evaluate the coupling 

stiffness values that arise from the slight asymmetry of the specimen. The analysis showed that 

in both the lower sublaminate and intact regions of the specimen, all coupling terms are zero 

except for the extension-bending coupling, B11, which was small relative to the corresponding 

terms in the A and D matrices. The relative bend-twist coupling, D16/D11, was also found to be 

very small (less than 1%). The upper sublaminate is balanced and symmetric, and hence, 

exhibits no coupling stiffness values. 

Specimen length (Ls=115mm) was chosen to result in a beam short enough to easily fit into 

a small tabletop load frame. Specimen width (B=12.7mm) was chosen in order to promote 

plane strain loading conditions in the specimen while maintaining a wide enough specimen to 

mitigate edge effects. Each specimen also contained an initial delamination length (a0 as 

defined in Figure 1) of 49mm. A strength of materials analysis was performed to assess the 

likelihood of arm failure during a test and found that such failure would not be likely. 

Test Fixture 

The test fixture is pictured in Figure 4 and was designed to enable adjustment of the 

specimen location along the span direction and also ensure precise alignment with respect to 

the fixture. Fixturing was also required to enable clamping of both ends of the specimen (as 

seen in Figure 4). The lower portion of the fixture consists of a grooved steel baseplate that is 

threaded directly into the test machine load cell (denoted as lower baseplate in Figure 4). A 

second steel plate (denoted as upper baseplate in Figure 4) mates with the baseplate using a 

tongue and groove type of connection. The specimen is clamped at both ends to the second 

plate as shown in Figure 4. Holes were drilled and threaded in the upper baseplate along the 

span direction, and shoulder screws were used as guide pins to enable precise specimen 

alignment (the holes are indicated in Figure 4). These screws were removed prior to each test 

once the specimen was securely clamped into the fixture. The specimen position along its 

length direction can be adjusted by sliding the upper baseplate over the lower baseplate, which 
4

is performed to ensure proper alignment of the piano hinge bonded to the specimen with the 

loading rod (see Figure 4). An array of four bolts secures both plates to each other, preventing 

further sliding during a test. Load is applied to a specimen via the 12.7mm-long piano hinge 

pictured in Figure 4. The load is applied to the specimen through a 300mm-long rod that is 

hinged at both ends. The top end is connected to the machine crosshead. The long loading 

arm minimized the introduction of horizontal loading that would otherwise accumulate as the 

specimen deforms. This method of mitigating horizontal loading is preferable over other 

methods, such as setting the baseplates on a moveable carriage, because fixture mass is 

minimized, making the entire apparatus more suitable for cyclic loading. 

The compliance of the test fixture was measured by loading a 12.7mm-wide, 6.35mm-thick 

steel bar that was fitted into the test fixture. The specimen was loaded up to the maximum force 

observed during actual tests (350N) at the mid-span via the same piano hinge configuration 

described previously. The fixture compliance was then computed by subtracting the compliance 

of the steel bar (computed using beam theory) from the compliance measured during the test. 

The fixture compliance was found to be 365x10-6mm/N, which was approximately 10% of the 

compliance of the SCB specimen that exhibited the smallest compliance. Although this 

relatively significant fixture compliance does not affect the observations made during the tests, 

specimen deformation at the load-application point was indicated by the crosshead 

displacement of the load frame, and hence, analyses conducted to simulate these tests should 

account for the fixture compliance. 

Specimen Load Introduction 

The load-application point on each specimen was positioned a distance, L, from the edge of 

the test fixture clamp as indicated in Figure 1. The distance, L, (also referred to as the ‘load 

offset’) was set to be greater than or equal to the initial delamination length, a0 (Figure 1). This 

load-offset range was chosen to promote delamination growth onset followed by migration of the 

delamination to a different ply interface. This was achieved by considering the following 

hypothesis. 

As the specimen is loaded (Figure 2a), the opening deformation in the vicinity of the PTFE 

insert front is coupled with the corresponding shear stress acting across it. This coupling mainly 

arises from the geometry of the specimen. However, the mismatch in bending stiffness of the 0-

degree ply and stack of four 90-degree plies below and above the PTFE insert, respectively, 

also contributes to this coupling. In the case of the loading configuration illustrated in Figure 2a 

(delamination length less than the load offset, i.e. a/L < 1), the shear stress acting across the 

PTFE insert front promotes kinking of the delamination towards the baseplate side of the 

specimen (the sign of the shear stress in this case is taken to be negative). However, the 0-

degree ply below the PTFE insert prevents this from occurring, and instead, delamination grows 

along the 0/90 ply interface. 

The delamination continues to propagate along the 0/90 interface and grows past the loadapplication point (such that a/L > 1, Figure 2b), eventually leading to a reversal of the sign of the 

shear stress (from negative to positive) acting across the delamination front. The shear stress 

now promotes kinking of the delamination into the 90-degree ply stack towards the loaded side 

of the specimen, which will occur once it is energetically favorable to do so. According to He 

and Hutchinson [26], this will occur when the following inequality is satisfied: 

Gk

GIc

>

G

Gc

 (1) 
5

where Gk is the maximum strain energy release rate for the kinked crack with respect to the kink 

angle, W (see Figure 2). The parameter GIc is the mode-I critical strain energy release rate of 

the material through which the kinked crack propagates (in this case the 90-degree ply stack). 

The parameters G and Gc are the strain energy release rate at the interface crack (in this case 

the 0/90 delamination) and the critical strain energy release rate at the interface, respectively. 

This analytical treatment is for isotropic solids, but in the case of the specimen, is expected to 

act as a reasonable guide because the 90-degree ply stack is transversely isotropic. 

The kinking crack will eventually propagate through the entire 90-degree ply stack and will 

transition into the interface between the ply stack and neighboring stack of three 0-degree plies, 

thereby completing the migration process. 

A series of finite element analyses were conducted in order to help corroborate the 

aforementioned hypothesis. Specimen dimensions used in the analyses are presented in 

Figure 5. Eleven analyses were performed, each with the specimen loaded at the mid-span but 

containing different delamination lengths, as illustrated in Figure 5. The analyses were 

conducted using the commercial code, ABAQUS®1

/Standard version 6.11 [31]. Solid, eightnode brick elements (ABAQUS® type C3D8i) were used to represent the specimen. A 

composite layer option was used to represent the specimen stacking sequence, whereby one 

layer of elements was used to represent one or more plies. In this case, the orthotropic ply 

properties [32] (see TABLE I for properties used in this analysis) were oriented according to the 

specimen stacking sequence. The 0/90 delamination was modeled by including elements with 

coincident nodes on the plane of the delamination. A fine mesh was used in the vicinity of the 

delamination front to accommodate for the rapid change in strain field. The element thickness 

at the delamination front (in the x-and z-axes) was one ply thickness. A similar meshing 

technique was adopted during an analysis of a double cantilever beam specimen [33]. An 

additional rectangular mesh was positioned in the location corresponding to the plate of the 

piano hinge. The hinge was represented as a linear-elastic isotropic material with standard 

properties of aluminum. Boundary conditions applied to the model are illustrated in Figure 5. 

Load application was simulated by prescribing a fixed displacement of 0.5mm in the z-direction 

along the row of nodes located at the point indicated in Figure 5. The same prescribed 

displacement was applied in each model in order to mimic the displacement-controlled condition 

of the actual tests. Coupled thermo-mechanical analyses were performed in order to capture 

the thermal residual stresses arising from the cure of the slightly non-symmetrical laminate (a 

total temperature gradient of 180o

C was assumed. The coefficients of thermal expansion 

assumed for IM7/8552 are listed in TABLE I). After each analysis run, the deformed region local 

to the delamination front (in the xz-plane) was observed and the sign of the shear deformation 

was recorded. 

The components of the strain energy release rate, GI, GII, and GIII, (average across the 

delamination front) were computed using VCCT [12,13] for each of the eleven delamination 

lengths. In each case, the crack tip element length was kept constant. Hence, although the 

strain energy release rate components are non-convergent [34], the overall effect of 

delamination length on these values is assumed to be accurate. The mode-II strain energy 

release rate as a percentage of the total strain energy release rate, GII/GT (where 

GT=GI+GII+GIII), is plotted in Figure 6 as a function of normalized delamination length, a/L. The 

plot shows that GII/GT oscillates in magnitude with a minimum close to zero at delamination 

lengths just greater than the load offset. It was noted that the shear stress acting across the 

delamination front would tend to favor delamination growth when a/L was less than or equal to 

 

ABAQUS® is manufactured by Dassault Systèmes Simulia Corp. (DSS), Providence, RI, USA.
6

1.05, as illustrated in Figure 6 (for convenience, shear stress sign in this case is negative). The 

values of GII/GT at which this was the case are plotted as open symbols and connected by a 

dashed line. At delamination lengths greater than the load offset (a/L > 1.05), the shear stress 

acting across the delamination front changed in sign (sign becomes positive, Figure 6) to favor 

kinking of the delamination into the 90-degree ply stack, as illustrated in Figure 6. The values of 

GII/GT at which this was the case are plotted as closed symbols connected by a solid line. 

Overall, the analysis results indicate that GII/GT diminishes to zero as the sign of shear stress 

reverses, and the conditions (shear stress sign) necessary to favor migration will occur when 

the delamination length is greater than 1.05L. Thus, the findings indicate that if the migration is 

controlled by the shear stress migration onset will change with load position of the specimen. 

Specimen Manufacture and Materials 

A 300mm-square plate of IM7/8552 tape laminate was laid up with the stacking sequence 

described earlier. A 127mm-wide strip of 12mm-thick PTFE was positioned across the plate 

between plies 22 and 23. The plate was cured in a hot press oven using the cure cycle 

suggested by the composite material manufacturer [35]. Upon completion of the cure cycle, a 

12.5mm-wide strip was cut from each side of the plate and 42 specimens were cut. A 15mmlong strip was cut from the end of the upper sublaminate of each specimen using a 0.4mmdiameter diamond wire, creating a protruding lip that was clamped during the tests (this lip is 

illustrated in Figure 1 under the left-hand clamp). A 0.02mm-thick metal shim was positioned 

along the delamination in the cut region to protect the neighboring specimen arm material as the 

saw approached the end of the cut. Specimens were stored in a desiccator for a period of 

approximately two months prior to testing. 

Delamination Migration Test Procedure 

Prior to testing, the edges of all specimens were polished to enable detailed examination of 

the plies under an optical microscope. Measurements of specimen width and thickness were 

then taken. The sides of each specimen were then coated with a thin layer of white paint to 

highlight the delamination and migration events as viewed from the sides of each specimen 

during a test.

Specimens had a constant pre-crack length of 49mm and were loaded with four different 

load offsets (Figure 1), namely, L=a0, 1.1a0, 1.2a0, and 1.3a0 (where a0=49mm). All load 

conditions were repeated four times except for L=1.3a0, which was only repeated three times. 

This resulted in a total of fifteen specimens being tested. 

The tests were conducted using a servo-hydraulic test machine equipped with a 450N load 

cell. Specimens were placed into the test fixture such that contact was made with both guide 

pins, ensuring precise specimen alignment. The specimens were secured to the upper 

baseplate of the test fixture via clamps at both ends. Three bolts secured the clamps and were 

tightened to a torque of approximately 900N-mm. After proper alignment was established with 

the specimen length perpendicular to the hinge axis, specimens were loaded under 

displacement control at a rate of 0.127mm/min in the direction indicated in Figure 1. Specimens 

were unloaded at the same loading rate. Applied load, P, and crosshead displacement, d

(referred to as displacement in the remainder of the paper), were recorded throughout each test. 

Delamination growth and migration was recorded by viewing both sides of each specimen using 

a pair of cameras equipped with macro lenses. Images of the delamination and migration 

events were recorded as they occurred during a test. The cameras were synchronized with the 

force and displacement output collected by the data acquisition system, enabling documentation 

of the exact force and displacement associated with each image. 
7

Post-Test Inspection 

After the completion of a test, both edges of the specimen were cleaned with alcohol to 

remove the white paint. The delamination and migration paths as viewed from both edges were 

inspected using an optical microscope at a 40-80X-magnification level. Specimens were then 

split along the existing delamination plane in order to confirm the PTFE insert front location. 

The fracture surfaces of a selection of specimens tested using each of the four load offsets were 

also inspected using a Philips XC30 scanning electron microscope. 

Results/Discussion

 Specimen Response and Fracture Events 

Loading Coincident with PTFE Insert Front 

The force/displacement responses of the four specimens with L=a0 are shown in Figure 7. 

As can be seen, the response of the specimens was very consistent. This was also true for the 

overall sequence of fracture events observed in each specimen. Included in Figure 7 are 

images of the events that were observed at various key moments during a test. The overall 

sequence of events was as follows: 1) specimens responded linearly to loading up to some 

critical force, 2) an unstable event took place once this critical force was reached. This event 

included unstable delamination growth that either arrested just prior to the onset of migration or 

began migrating through the upper 90-degree ply stack to be arrested part way through the 

stack. Total delamination growth prior to migration ranged between 8 and 9mm, 3) loading of 

the specimens was continued (all specimens appeared to respond elastically at this stage) until 

a second critical force at which point a second unstable event occurred. This event involved 

migration of the delamination via a kinking crack through the upper 90-degree ply stack. Further 

loading resulted in stable growth of the migrated delamination, 4) specimens responded linearly 

to unloading, and exhibited a residual displacement of approximately 0.12mm 

Inspection of the specimen edges under an optical microscope indicated that after growth 

onset from the PTFE insert, the delamination grew directly along the 0/90 interface for 

approximately 1mm after which point the delamination seemed to transition into the lower 0-

degree ply (see circled number 1 in Figure 8). This transition into the 0-degree ply, however, is 

likely only a free surface edge effect because as will be shown in a later fractographic 

examination of the delamination surface, no evidence of migration into the 0-degre ply was 

observed. The delamination appeared to skim the top of the 0-degree ply until just prior to 

migration, at which point the delamination appears to transition more to the 90-degree ply 

side of the interface (see circled number 2 in Figure 8) and gradually kinks through the upper 

90-degree ply stack. Upon initial consideration, this observation seems to contradict the 

argument put forward in the previous section concerning load introduction, where it was 

postulated that the lower 0-degree ply will confine delamination growth prior to migration exactly 

to the 0/90 interface. This argument is thought to still hold, however, and the observed growth 

path is explained by the fact that fibers in the 0-degree ply are not parallel and perfectly aligned 

along this direction. This provides an opportunity for cracks to grow between misaligned fibers, 

particularly when the shear stress (Figure 2a) promotes kinking of the delamination through the 

lower 0-degree ply. Evidence of this occurrence was also found during the fractographic 

analysis presented later in the paper. As it is still energetically unfavorable for the delamination 

to completely kink through the 0-degree ply, delamination proceeds near the 0/90 interface. As 

the delamination grows further, the shear stress changes sign, favoring kinking through the 90-

degree ply stack, which gradually occurs as it becomes energetically favorable to do so (in a 

manner similar to that described by He and Hutchinson [26]). Ultimately, the kinking crack 
8

grows towards the interface between the top of the 90-degree ply stack and a stack of 0-degree 

plies, resulting in onset of delamination growth along this interface, thereby completing the 

migration process. The relatively sudden exit of the kinked crack into the new 90/0 interface is 

indicative of the kinked crack having established a constant path of least resistance though the 

upper portion of the 90-degree ply stack (as evidenced by the linear appearance of the kink in 

this portion of the 90-degree ply stack), whereby the conditions that were energetically favorable 

for the kinking crack to reside locally at this 90/0 interface. The kink angle, W, is thus defined as 

the angle to the horizontal direction made by a line parallel to the linear portion of the kinked 

crack in the 90-degree ply stack, as illustrated in Figure 8. Further discussion regarding kink 

angles follows later in this section. 

Load Offset, L=1.1a0, 1.2a0, and 1.3a0

The force/displacement responses of a specimen with load offsets equal to 1.1a0, 1.2a0, and 

1.3a0 are presented in Figures 9a, 9b, and 9c, respectively. Each case shown in the figures is 

typical of the other specimens tested at the three loading configurations. Specimens with the 

smallest load offset (L=1.1a0) exhibited initial linear loading followed by stable delamination 

growth onset resulting in a small (approximately 1mm) amount of growth. This was followed by 

an unstable event that included unstable delamination growth along the 0/90 ply interface and 

migration, the onset of which ranged between 10-14mm past the load-application point, as 

illustrated in Figure 9a. The distance between the load application point and the onset of 

migration is denoted as Dk in Figure 9. Specimens unloaded in a linear fashion ending with a 

residual displacement of approximately 0.12mm. 

Specimens with load offsets equal to 1.2a0 and 1.3a0 behaved in a very similar manner to 

specimens whose load application was coincident with the PTFE insert front and exhibited the 

same sequence of events described previously for these specimens. In the case of the L=1.2a0

offset specimens, delamination migration onset took place 7-10mm past the load-application 

point. Delamination migration onset in the L=1.3a0 offset specimens took place 6-9mm past the 

load-application point. 

The perceived path of the fracture events was similar in all specimens to those indicated in 

Figure 8. 

Effect of Load Offset on Migration 

The plot in Figure 10a shows the distance from the load-application point at which 

delamination migration onset was observed (Dk) as a function of the load offset, L, normalized 

by the initial delamination length, a0. Although the scatter in these data (between repeat 

specimens at each load offset) is quite high at a given load offset, the overall data tend to show 

that migration onset occurs closer to the load-application point as the load offset increases 

(migration onset in specimens with a load offset, L=a0, was an exception to this rule). One 

possible explanation for this effect is that the mixed-mode loading conditions acting on the 

delamination front prior to migration are likely affected by the position of the load application 

point. This in turn will affect the apparent fracture toughness of the interface along which the 

delamination is growing and so will ultimately affect the location along the interface at which 

conditions favorable for kinking into the 90-degree ply stack will arise. An alternative 

explanation is that the speed of delamination growth may affect the fracture toughness of the 

interface and therefore affect the moment at which migration takes place. However, in all cases 

migration took place during seemingly similar unstable events, which does not seem to support 

delamination growth speed as a possible factor. A plot of kink angle versus load offset is given 

in Figure 10b. The scatter in these data is quite high and possibly masks any trend that may 

otherwise have been observed. The average kink angle was 61o

 with a standard deviation of 
9

9.8o. This does suggest that kink angle was independent of load offset. Further analysis of kink 

angle is required before a more reliable conclusion can be offered. The data plotted in Figure 

10 are also given in TABLE II. 

Fractography 

The fracture surfaces of a specimen from each of the four load offsets were inspected in a 

Philips XC30 scanning electron microscope. Micrographs taken of a specimen with a load 

offset, L=1.3a0, are presented in Figure 11. A total of ten images were taken, including five 

images along the central portion of the specimen, as illustrated on the sketch in Figure 11, and 

another five images near the specimen edge to the right of the central images. These latter 

images where similar to their central counterparts and so only the central images are shown. 

Beginning with the micrograph taken near to the PTFE insert front, this region contains clean 

looking 0-degree fibers with what appear to be shear hackles nested between a number of the 

fibers. This indicates a mixed mode-I/II form of loading as is expected along this 0/90 interface. 

The appearance of clean 0-degree fibers also indicate that the delamination is attempting to 

kink into the 0-degree ply but is ultimately prevented from doing so. As the delamination 

propagates to Region 2 in the specimen (see Figure 11), the fracture surface contains mostly 

imprints of 0-degree fibers. This indicates a transition of the propagating delamination away 

from the 0-degree ply. The surface of the beginning of the kinking crack in the 90-degree ply 

stack (Region 3) contains broken fibers, but overall the surface has a clean appearance. The 

fracture surface of the kinked crack in the middle of the 90-degree ply stack (Region 4) has 

clean looking broken fibers and regions of rotated shear hackles. The broken fibers indicate 

that kinking did not take place along a single plane, possibly indicating the fibers in this ply stack 

may not be aligned exactly along the 90-degree direction and parallel to one another. It is 

postulated that the generally clean looking surface is evidence of the kink being mode I 

dominated with regions of local mode III fracture, which occurs as 90-degree fibers deform and 

separate from one another. The final image (region 5) shows the beginning of the migrated 

delamination whose surface contains river lines that are indicative of mode-I dominated fracture 

[36]. 

To summarize, inspection of the specimen fracture surfaces indicates that delamination 

growth prior to migration takes place under a mixed mode-I/II form of loading. The kinked crack 

in the 90-degree ply stack appears to propagate under a predominantly mode-I form of loading, 

which is also the case for the migrated delamination. Images taken of fracture surfaces of all 

other specimens indicated a similar sequence of fracture events to that described above. 

However, additional microscopy will need to be performed to help evaluate the above 

summation and confirm that the observations from this fractographic analysis are consistent 

with specimens tested with load offsets of a0, 1.1a0, and 1.2a0.

Concluding Remarks 

A new test method has been developed for observing and documenting the migration of a 

propagating delamination. The test relies on the shear loading acting locally across the 

delamination for controlling the sequence of fracture events. The location in the specimen at 

which delamination migration onset occurred was found to be affected by the position of the 

load-application point (load offset). This is likely due to the change in load offset altering the 

mixed mode loading that drives the delamination prior to migration and thus changes the 

position at which migration onset becomes energetically favorable. Speed of delamination 

growth may also affect the fracture toughness of the interface and therefore affect the moment 

at which migration takes place. However, in all cases migration took place during seemingly 
10

similar unstable events, which would not seem to support this hypothesis. Kink angle was found 

to be independent of load offset, although further analysis is required before a more concrete 

conclusion can be offered. A fractographic analysis of the fracture surfaces of the specimens 

indicated that initial delamination is driven by a mixed mode-I/II form of loading while the crack 

that kinks into the 90-degree ply stack is largely driven by a mode-I form of loading. The same 

mode-I dominated form of loading was observed in the migrated delamination. In general, use 

of this test allows for the observation of the growth of a delamination followed by migration of 

the delamination to another ply interface, and should thus provide a means for validating 

analyses aimed at simulating migration. 

References

1. Pipes, R. B. and N. J. Pagano. 1970. “Interlaminar Stresses in Composite Laminates Under 

Uniform Axial Extension,” Journal of Composite Materials, 4:538-548. 

2. Kima, J-K., D. B. MacKaya, and W-Y. Mai. 1993. “Drop-Weight Impact Damage Tolerance of 

CFRP with Rubber-Modified Epoxy Matrix,” Composites, 24(6):485–494. 

3. ASTM D5528-01 “Standard Test Method for Mode I Interlaminar Fracture Toughness of 

Unidirectional Fiber-Reinforced Polymer Matrix Composites,” 2004 Annual Book of ASTM 

Standards, Vol.15.03. 

4. Davidson, B. D. and S. S. Teller. 2010. “Recommendations for an ASTM Standardized Test 

for Determining GIIc of Unidirectional Laminated Polymeric Matrix Composites,” Journal of 

ASTM International, 7(2):Paper ID JAI102619. 

5. Brunner, A. J., B. R. K. Blackman, and P. Davies. 2008. “A Status Report on Delamination 

Resistance Testing of Polymer–Matrix Composites,” Engineering Fracture Mechanics,

75:2779–2794. 

6. Lee, S. M. 1993. “An Edge Crack Torsion Method for Mode III Delamination Fracture 

Testing,” Journal of Composites Technology and Research, JCTRER, 15(3):193-201. 

7. ASTM D6671M-04 “Standard Test Method for Mixed Mode I-Mode II Interlaminar Fracture 

Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites,” 2004 Annual 

Book of ASTM Standards, Vol.15.03. 

8. ASTM D6115-04 “Standard Test Method for Mode I Fatigue Delamination Growth Onset of 

Unidirectional Fiber-Reinforced Polymer Matrix Composites,” 2004 Annual Book of ASTM 

Standards, Vol.15.03. 

9. O'Brien, T. K., W. M. Johnston, and G. J. Toland. 2010. “Mode II Interlaminar Fracture 

Toughness and Fatigue Characterizarion of a Graphite Epoxy Composite Material,” NASA

Technical Memorandum, NASA/TM-2010-216838. 

10. Brunner, A. J. and P. Flueler. 2005. “Prospects in Fracture Mechanics of Engineering 

Laminates,” Engineering Fracture Mechanics, 72(6):899–908. 

11. Raju, I. S. and T. K. O’Brien. 2008. “Fracture Mechanics Concepts, Stress Fields, Strain 

Energy Release Rates, Delamination Initiation and Growth Criteria,” in Delamination 

Behavor of Composites, E. Sridharan, ed. Woodhead Publishing Limited, pp. 3-27. 

12. Rybicki, E. F. and M. F. Kanninen. 1977. “A Finite Element Calculation of Stress Intensity 

Factors by a Modified Crack-Closure Integral,” Engineering Fracture Mechanics, 9:931-938. 

13. Krueger, R. 2004. “Virtual Crack Closure Technique: History, Approach, and Application,” 

Applied Mechanics Reviews, 57(2):109-143. 

14. Dugdale, D. 1960. “Yielding of Steel Sheets Containing Slits,” Journal of the Mechanics and 

Physics, 8:100–104. 

15. Barenblatt, G. 1962. “The Mathematical Theory of Equilibrium Cracks in Brittle Fracture,” 

Advances in Applied Mechanics, 7:55–129. 
11

16. Camanho, P. P., C. G. Davila, and D. R. Ambur. 2001. “Numerical Simulation of 

Delamination Growth in Composite Materials,” NASA Technical Publication, NASA-TP211041. 

17. Goyal, V. K., E. R. Johnson, and C. G. Davila. 2004. “Irreversible Constitutive Law for 

Modeling the Delamination Process Using Interfacial Surface Discontinuities,” Composite 

Structures, 65:289-305. 

18. Hull, D. and Y. B. Shi. 1993. “Damage Mechanisms Characterization in Composite Damage 

Tolerance Investigations,” Composite Structures, 23(2):299-120. 

19. Cantwell, W. J. and J. Morton. 1991. “The Impact Resistance of Composite Materials — A 

Review,” Composites, 22(5):347–362. 

20. Krueger, R., M. K. Cvitkovich, T. K. O'Brien, and P. J. Minguet. 2000. “Testing and Analysis 

of Composite Skin/Stringer Debonding under Multi-Axial Loading,” Journal of Composite 

Materials, 34(15):1263-1300. 

21. Owsley, G. S. 2000. “The Effect of Z-Fibre Reinforcement on Fatigue Properties of Stiffened 

Composite Panels,” Presented at the 15th Technical Conference of the American Society for 

Composites, Texas, September 25-27. 

22. Hallett, S. R., B. G. Green, W-G. Jiang, K. H. Cheung, and M. R. Wisnom. 2009. “The Open 

Hole Tensile Test: A Challenge for Virtual Testing of Composites,” International Journal of 

Fracture, 158:169-181. 

23. Belytschko, T., R. Gracie1, and G. Ventura. 2009. “A Review of Extended/Generalized Finite 

Element Methods for Material Modeling,” Modelling and Simulation in Materials Science and 

Engineering, 17(4):1-24. 

24. Yang, D. L. and B. Cox. 2009. “An Augmented Finite Element Method for Modeling Arbitrary 

Discontinuities in Composite Materials,” International Journal of Fracture, 156(1):53-73. 

25. Moës, N., J. Dolbow, and T. Belytschko. 1999. “A Finite Element Method for Crack Growth 

Without Remeshing,” International Journal for Numerical Methods in Engineering,

46(1):131–150. 

26. He, M-Y., and J. W. Hutchinson. 1989. “Kinking of a Crack Out of an Interface,” Journal of 

Applied Mechanics, 56:270-278. 

27. Wang., T. C. 1994. “Kinking of An Interface Crack Between Two Dissimilar Anisotropic 

Elastic Solids,” International Journal of Solids and Structures, 31(5):629-641. 

28. Canturri, C., E. S. Greenhalgh, S. T. Pinho, and J. Ankersen. “Delamination Growth 

Directionality and the Subsequent Migration Processes – The Key to Damage Tolerant 

Design,” Presented at the 15th European Conference on Composite Materials, Venice, Italy, 

24-28 June, 2012. 

29. Greenhalgh, E.S., C. Rogers, and P. Robinson. 2009. “Fractographic Observations on 

Delamination Growth and the Subsequent Migration Through the Laminate,” Composites 

Science and Technology, 69:2345-2351. 

30. Jones, M. J. 1999. “Mechanics of Composite Materials,” Taylor and Francis. 

31. ABAQUS®/Standard Ver. 6.11 User’s Manual, 2011. 

32. O'Brien, T. K. and R. Krueger. 2003. “Analysis of Flexure Tests for Transverse Tensile 

Strength Characterization of Unidirectional Composites,” Journal of Composites Technology 

and Research, JCTRER, 25:50-68. 

33. Krueger, R., and T. K. O'Brien. 2001 “A Shell/3D Modeling Technique for the Analysis of 

Delaminated Composite Laminates,” Composites Part A: Applied Science and 

Manufacturing, 32:25-44. 

34. Raju, I. S., J. H. Crews Jr, and M. A. Aminpour. 1988. “Convergence of Strain Energy 

Release Rate Components for Edge-Delaminated Composite Laminates,” Engineering 

Fracture Mechanics, 30(3):383-396. 

35. Hexcel Corporation, 2007. “HexPly® 8552 Product Data Sheet,” http://hexcel.com.

36. Greenhalgh, E.S. 2009. “Failure Analysis and Fractography of Polymer Composites,” 

Woodhead Publishing In Materials. 
12 

Figure 1. Schematic of delamination migration specimen. 

Figure 2. Shear stresses acting across the delamination front at different stages of a test. 

300.0 

Clamp 

Clamp 

a0=49 

12.7 

12.7 

L 

S = 115 Baseplate 

Specimen 

[0]3

[90]4

[0] 

[90]4

[0]2

Applied 

load 

0o h=5.25 

2mm gap 

All units in mm. Not drawn to scale 

Specimen width (y-axis), 

B=12.7mm 

90o

-direction parallel to y-axis 

[0]3 

[90]4 

[0] 

[90]4

[0]3 

[90]4 

[0] 

[90]4

a/L > 1 

a

a/L < 1 

L 

L 

a (a) (b) 

Ω 

Principal tensile 

stress plane 

Principal tensile 

stress plane 

-ve 

+ve 
13 

Figure 3. Stacking sequence of delamination migration specimen. 

Figure 4. Delamination migration test fixture with loaded specimen (L=1.1a0). 

Symmetric stacking sequence (condensed): 

{[904/03/(90/0)2]s}s

Symmetric stacking sequence (expanded): 

[904/03/(90/0)2s/03/904/ T /904/ /0/0/(90/0)2s/0/0/ /904] 

Actual specimen stacking 

sequence: 

[904/03/(90/0)2s/03/904/ T / /904/0/0/(90/0)2s/0/0/903/ /90] 

Notes: 

Sequence of plies: Left to right corresponds to upper to lower 

surfaces of the specimen. 

Lower baseplate 

Upper baseplate 

Loading rod 

Guide pin holes Specimen 

Piano hinge 
14

Figure 5. Finite element mesh of a specimen (mesh along z-axis expanded to aid view). 

Figure 6. GII/GT as a function of normalized delamination length, a/L. 

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 

GII/GT

a/L 

Constraints on surface 

nodes in this region: 

u=v=w=0 

Constraints on surface 

nodes in this region: 

w=0.5mm u=v=w=0 

z, w 

x, uy, v 

12.7mm 

102mm 

12.7mm 

Specimen width (y-axis), B=12.7mm 

Aluminum Young’s modulus: 70000N/mm2

Aluminum Poisson’s ratio: 0.35 

Eleven analyses with the following delamination lengths, a, were 

conducted: 

a/L=0.75, 0.80, 0.85, 0.90, 0.95,1.00, 1.05, 1.10, 1.15, 1.20, 1.25 

i ) B 12 7

a

5.5mm 

L=51mm 

-ve

+ve 

-ve +ve 
15

Figure 7. Force/displacement response of specimens loaded coindicentally with PTFE 

insert front. 

Figure 8. Micrographs of delamination onset and migration regions in a specimen. 

0

50

100

150

200

250

300

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 

Force

N

Displacement, mm 

k =8-9mm 

L=a0

0o/90o interface 

Teflon 

[90]4 tip

[0]

[90]4

[0]3

[90]4

[0]



1

2

0.1mm 0.2mm 

 0o

/90o interface 
16

Figure 9. Force/displacement response of specimens (a) L=1.1a0, (b) L=1.2a0, (c) L=1.3a0.

0

50

100

150

200

250

300

350

400

450

500

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 

Force

N

Displacement, mm 

0

50

100

150

200

250

300

350

400

450

500

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 

Force

N

Displacement, mm 

0

50

100

150

200

250

300

350

400

450

500

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 

Force

N

Displacement, mm 

L=1.1a0

k =10-14mm 

L=1.3a0 k=6-9mm

L=1.2a0 k =7-10mm

(a) 

(b) 

(c) 
17

Figure 10. Effect of load-application offset, L, on, (a) location of delamination migration 

onset, (b) Kink angle. 

0

2

4

6

8

10

12

14

16

1.00 1.10 1.20 1.30 1.40 

Load offset, L/a0

0

10

20

30

40

50

60

70

80

90

1.00 1.10 1.20 1.30 1.40 

Load offset, L/a0

(b) 

Migration onset 

distance, 

k

 (mm)

(a) 

4

5 Kink angle, 

(degrees)
18

Figure 11. Scanning electron micrographs of specimen fracture surfaces (L=1.3a0).

5

4

3

2

1

PTFE 

insert 

Kinked area 

50m

1

50m

2

20m

3

50m

4

50m

5

Mode-I dominated 

delamination 
19 

TABLE I. MATERIAL PROPERTIES OF IM7/8552 

E11 = 161.0 GPa E22 = 11.38 GPa E33 = 11.38 GPa 

n12 = 0.32 n13 = 0.32 n23 = 0.436 

G12 = 5.17 GPa G13 = 5.17 GPa G23 = 3.98 GPa 

CTE (fiber direction) =-0.1E-6 1/K 

CTE (transverse direction) =31E-6 1/K 

 

TABLE II. DATA FROM DELAMINATION MIGRATION TESTS 

Specimen 

Load offset 

L 

(mm) 

Normalized 

load offset 

L/a0

Relative* 

migration onset 

location, Δk

(mm) 

Kink angle

W 

(degrees) 

SCB31 49.00 1.00 8.60 65 

SCB35 48.55 0.99 8.75 74 

SCB40 48.30 0.99 8.75 65 

SCB42 49.00 1.00 9.22 68 

SCB32 54.10 1.10 12.35 65 

SCB36 53.90 1.10 10.70 52 

SCB37 54.05 1.10 13.75 47 

SCB39 53.70 1.10 11.05 53 

SCB24 58.90 1.20 7.00 52 

SCB26 58.95 1.20 8.90 67 

SCB34 59.35 1.21 8.80 78 

SCB41 59.25 1.21 8.30 68 

SCB33 64.55 1.32 6.30 55 

SCB38 63.55 1.30 8.80 45 

SCB44 63.80 1.30 7.95 60 

* Distance relative to the load-application point. 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

A Test for Characterizing Delamination Migration in Carbon/Epoxy Tape 

Laminates 

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Ratcliffe, James G.; Czabaj, Michael W.; O'Brien, Thomas K.

 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-2199

 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

L-20305

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 24

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email: help@sti.nasa.gov)

14. ABSTRACT

A new test method is presented for the purpose of investigating migration of a delamination between neighboring ply interfaces in fiber-reinforced, polymer 

matrix tape laminates. The test is a single cantilever beam configuration consisting of a cross-ply laminate with a polytetrafluoroethylene insert implanted at 

the mid-plane and spanning part way along the length of the specimen. The insert is located between a 0-degree ply (specimen length direction) and a stack of 

four 90-degree plies (specimen width direction). The specimen is clamped at both ends onto a rigid baseplate and is loaded on its upper surface via a piano 

hinge. Tests were conducted with the load-application point located on the intact portion of the specimen in order to initiate delamination growth onset 

followed by migration of the delamination to a neighboring 90/0 ply interface by kinking through the 90-degree ply stack. Varying this position was found to 

affect the distance relative to the load-application point at which migration initiated. In each specimen, migration initiated by a gradual transition of the 

delamination at the 0/90 interface into the 90-degree ply stack. In contrast, transition of the kinked crack into the 90/0 interface was sudden. Fractography of 

the specimens indicated that delamination prior to migration was generally mixed mode-I/II. Inspection of the kink surface revealed mode-I fracture. In 

general, use of this test allows for the observation of the growth of a delamination followed by migration of the delamination to another ply interface, and 

should thus provide a means for validating analyses aimed at simulating migration. 

15. SUBJECT TERMS

delamination; migration; test method

18. NUMBER

 OF 

 PAGES

24

19b. TELEPHONE NUMBER (Include area code)

(443) 757-5802

a. REPORT

U

c. THIS PAGE

U

b. ABSTRACT

U

17. LIMITATION OF 

 ABSTRACT

UU

Prescribed by ANSI Std. Z39.18

Standard Form 298 (Rev. 8-98)

3. DATES COVERED (From - To)

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

794072.02.07.03.03

11. SPONSOR/MONITOR'S REPORT

 NUMBER(S)

NASA/TM-2013-218028

16. SECURITY CLASSIFICATION OF:

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 

collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and 

Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person 

shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

1. REPORT DATE (DD-MM-YYYY)

01- 08 - 2013