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Bearing Strength and Damage Progress for PAN-Based and Pitch-Based Carbon Fiber Composites

SAGE Publications Inc
Journal of Composite Materials
Authors:
Hironori Maikuma
Hironori Maikuma
Hironori Maikuma
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Kenji Kubomura
Kenji Kubomura
Kenji Kubomura
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Abstract

Two bearing strengths are characterized for four PAN-based and four pitch-based carbon fiber composites of [0°/±45°/90°]3s laminate. It is found that full bearing strength is developed when the edge distance ratio, e/D, is equal to or greater than 3.0 and the side distance ratio, w/D, is equal to or greater than 4.0. Bearing strength in creases with an increase in the fiber strain to failure, and also with the longitudinal com pressive strength of the unidirectional composites. No correlation is evident between the tensile strength of fiber and the bearing strengths. The first peak load in the load versus pin displacement curve is recommended for calculating the bearing strength.
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1739
Bearing
Strength
and
Damage
Progress
for
PAN-Based
and
Pitch-Based
Carbon
Fiber
Composites
HIRONORI
MAIKUMA*
AND
KENJI
KUBOMURA
Chemicals
Advanced
Materials
&
Technology
Research
Laboratories
Nippon
Steel
Corporation
1618
Ida,
Nakahara
Kawasaki
211,
Japan
(Received
September
30,
1992)
(Revised
June
22,
1993)
ABSTRACT:
Two
bearing
strengths
are
characterized
for
four
PAN-based
and
four
pitch-based
carbon
fiber
composites
of
[0°/±45°/90°]
3s
laminate.
It
is
found
that
full
bearing
strength
is
developed
when
the
edge
distance
ratio,
e/D,
is
equal
to
or
greater
than
3.0
and
the
side
distance
ratio,
w/D,
is
equal
to
or
greater
than
4.0.
Bearing
strength
in-
creases
with
an
increase
in
the
fiber
strain
to
failure,
and
also
with
the
longitudinal
com-
pressive
strength
of
the
unidirectional
composites.
No
correlation
is
evident
between
the
tensile
strength
of
fiber
and
the
bearing
strengths.
The
first
peak
load
in
the
load
versus
pin
displacement
curve
is
recommended
for
calculating
the
bearing
strength.
KEY
WORDS:
composites,
PAN/pitch-based
carbon
fiber,
fiber
property,
bearing
strength,
damage
progress.
INTRODUCTION
IBER
COMPOSITES
HAVE
been
used
extensively
in
the
recreational,
aero-
F nautical
and
industrial
fields
in
the
past
few
decades.
Since
structures
consist-
ing
of
composite
members
are
getting
larger
and
more
complex,
the
joining
of
several
structural
members
is
becoming
more
and
more
common,
and
design
is
more
often
dictated
by
the
structural
joint
strength.
Thus,
many
papers
dealing
with
mechanically
fastened
joints
have
been
published
[1-13]
for
carbon
fiber
composites
[5-12].
There
have
been
significant
improvements
in
fiber
properties;
tensile
strength,
elastic
modulus
and
strain
to
failure,
since
carbon
fibers
became
commercially
available
in
the
early
1960s.
As
a
result,
various
types
of
carbon
fibers,
which
*Author
to
whom
correspondence
should
be
addressed
Journal
of
COMPOSITE
MATERIALS,
Vol.
27,
No.
18/1993
0021-9983/93/18
1739-23
$6.00/0
@
1993
Technomic
Publishing
Co.,
Inc
... Moreover, as the failure of joints is remarkably affected by geometric parameters, the influence of design parameters on the failure of joints has been highly focused on in large amounts of literatures. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Generally, double-lap bolted joints contain five independent failure modes, which are laminate bearing, net tension, shear out, tear out and cleavage, and their combinations. 23,25 The failure modes of the joints relate to material properties, geometric dimensions, layups, etc. ...
... Over the past four decades, many experimental investigations of the influence of E/D on the failure of joints have been carried out. [6][7][8][9][10][11][12][13][14] Hart-Smith 6 found that when E/D changed from 3 to 2, either a shearing or a cleavage failure mode would replace the expected bearing failure mode for graphite-glass-epoxy (T300/ N5208 and S1014/N5208) laminates with quasi-isotropic or two near-quasi-isotropic layups. But for graphite-epoxy (T300/N5208) laminates with the same plies, bearing failure occurred when E/D dropped to 2. Kweon et al. 7 got the conclusion that a shearing mode rather than a bearing failure mode occurred if changing E/D from 2 to 1 for pin-load laminates made of USN125 graphite/epoxy unidirectional prepreg and DMS2288 woven prepreg with layups [(AE45) 3 /90/(AE45) 2 /0 4 /90/0 4 /(AE45) 2 /90/(AE45) 3 ]. ...
Influence of end distances on the failure of composite bolted joints
Article
Full-text available
To explore the physical effect of end distances on mechanical behaviors of composite bolted joints, series of single-bolt composite joints designed with different end distances were tested. In conjunction with the experimental work, a numerical progressive damage method is introduced to trace the damage process from the onset and propagation up to ultimate failure of the joints. A group of material degradation factors is presented by a trial-and-error method to establish three-dimensional progressive damage models of the bolted joints. The progressive damage analyses show that the predicted load–displacement curves, failure loads, and failure patterns of bolted joints with different end distances are in good agreements with the related experimental outcomes. From the experimental and numerical results, it follows that the cleavage failure gradually switches to the bearing failure with the increasing ratio of E/D ranged from about 2 to 4. An economic and suitable ratio of E/D ≈ 3 is provided for the bolted joints made of X850 carbon/epoxy composites with balanced and symmetric layups [45/0/−45/0/90/0/45/0/−45/0]s. The understanding of the effect of E/D on the mechanical behaviors including the strength, stiffness, and failure patterns of single-bolt joints is strengthened.
View
... Khashaba et al. [7] and Hollmann [14] calculated the bolt bearing strength based on the ultimate failure loads. The bearing stress is defined by the first-peak load by many investigators [15][16][17]. Irisarri et al. [17] reported that compared to the conventional definitions of bearing failure based on a 2% offset strength criterion or the alternative 4% HD, the first-peak bearing load presents the advantage of being physically based. This because the standard criteria were conceals variables and possibly significant levels of damage in the joint. ...
... The failure load (P) was defined by two different levels. The first load level is the load at the first-peak of the loaddisplacement curve, which define the bearing strength [15][16][17]. ...
Failure and Reliability Analysis of Pinned-Joints Composite Laminates: Effects of Stacking Sequences
Article
Full-text available
  • Sep 2012
  • COMPOS PART B-ENG
The present work deals with the failure and reliability analysis of composite pinned-joints using theoretical models based on Weibull distribution function with experimental results for a guideline of safe design strength, which are not studied yet. The purpose of this work is to study the failure and reliability analysis of pinned-joints in glass-fiber reinforced epoxy composites. The influence of specimen stacking sequences on the mean bearing strength, mean ultimate failure stress, failure displacement and bearing stiffness was investigated. Four configurations were studied: [0/90](2s), [15/-75](2s), [30/-60](2s), and [45/45](2s). The results showed that the apparent bearing stiffness was qualitatively agreed with the predicted Young's modulus. Specimens with [0/90](2s) stacking sequence have the maximum failure displacement and ultimate failure stress compared with the other stacking sequences. On the other hand, specimens with [45/-45](2s), stacking sequence have the maximum failure displacement and bearing capacity based on the first-peak criterion. Theoretical models have been developed to predict the characteristic bearing strength, lower bound bearing strength, and safe design bearing strength at different reliability levels. These models show that the penalty paid to gain high reliability bearing strength, R = 0.99, in some cases, was more than 50% of the mean value. (c) 2012 Elsevier Ltd. All rights reserved.
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... A series of pin-bearing ASTM D5961 tests were conducted on both dry and wet conditions for all specimens using a universal testing machine (Testometric 200 kN) at room temperature. Standard test specimens were used to obtain bearing failure mode rather than net tension or shear-out modes that had lower loads associated with catastrophic fracture as recommended by previous studies 31,32 . The dimensions of the standard test specimen are illustrated in Fig. 3a where w/d = 6 and e/d = 6. ...
Study of bearing strength for injection molded GFRPP composites under dry and wet conditions
Article
Full-text available
  • Oct 2022
Thermoplastics and fiber-reinforced thermoplastics represent great deals in nowadays industries and applications where some of these applications are projected to wet environment. The present study investigates the effect of water moisture on the bearing strength (BS) of Polypropylene (PP) and glass fiber (GF) reinforced Polypropylene (GFRPP) composites. PP and GFRPP are produced by injection molding using different GF weight fractions (wt%), 10, 20, and 30 wt%, and two different initial fiber lengths 12 and 24 mm. A burnout test indicated that produced specimens with 12 mm long fibers have higher final fiber lengths than those made of 24 mm long fibers. More water was absorbed for higher GF weight fractions. The results of the dry bearing test showed higher bearing strengths for specimens with higher GF wt% and longer fibers. The same observation was obtained from wet tests, while, wet-tested specimens of all compositions have higher strengths than their dry counterparts. Strain-at-break seemed to be significantly reduced by water absorption for all specimens. Specimens tested in wet conditions have different fracture morphology than dry ones due to the change in the mechanical behavior of the materials after water immersion.
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... A series of pin-bearing ASTM D5961 tests were conducted on both molded-in and drilled specimens with different fiber contents using a universal testing machine (Testometric 200 kN) at room temperature. Standard test specimens were used to obtain bearing failure mode rather than net tension or shear-out modes that had lower loads associated with catastrophic fracture as recommended by previous studies 20, [57][58][59] . The dimensions of the standard test specimen are illustrated in Fig. 2a where w/d = 6 and e/d = 6. ...
Comparison between bearing strengths of molded‑in and machined holes of GFR/PP composites
Article
Full-text available
  • Aug 2022
This study is an investigation of weight fraction (wt%) and fiber feedstock length (FFSL) effects on the bearing strength (BS) of bolted joints in glass‑fiber‑reinforced (GFR) polypropylene (PP) composites manufactured by an injection molding technique. The investigation was made for holes produced either by molding or machining. For machined holes, the effect of drilling parameters (feed and speed) on BS was discussed. It is observed that BS decreased as FFSL increased. BS of both molded‑in and drilled specimens was enhanced by increasing wt% of glass fiber. While slightly better BS was observed for molded‑in specimens than drilled ones for all specimens. The drilling conditions’ effect on BS was found to be insignificant for drilled holes in long fibers reinforced PP, where the most significant factor was wt%. However, for short fibers reinforced PP, the spindle speed was the most significant factor followed by feed, while wt% has the lowest effect. Failure morphology mode for specimens indicates that for molded‑in specimens, neat PP specimens failed under pure bearing mode while GFR/PP specimens failed under the mixed‑mode failure (bearing and net tension). For machined specimens, all specimens failed under mixed‑mode failure except for the highest wt% specimens which failed under net tension.
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... Bearing strength is defined as the value of bearing stress occurring at a significant event on the bearing stress-bearing strain curve [3]. The various bearing failure criteria, include: (a) 2% offset bearing strength criterion [4], ASTM D D5961, (b) first peak load of load-pin displacement curve [5][6][7], (c) bearing failure as the maximum load just prior to unstable, nonlinear behavior [8], (d) 4% hole deformation strength (HDS) [9], ASTM D953, (e) ultimate failure loads [1,9,10], (f) ultimate bearing strain [11], and (g) a 5% stiffness drop has been proposed by Camanho and Lambert [12]. The actual definition of the bearing strength is not going to influence the output of this study in which the bearing stresses were determined at the first peak load, ultimate load and 4% hole deformation load. ...
View
... The static ultimate bearing strength is defined in ASTM D953 as the stress that causes elongation (deformation) = 4% of the original hole diameter (D). Maikuma and Kubomura [11] reported in their review two failure criteria for calculating the bearing strength of FRP composites. The first criterion was based on the half of the maximum bearing load, while the second criterion was based on the first peak load, using the load-pin displacement curve. ...
INFLUENCE OF WASHER SIZE AND TIGHTENING TORQUE ON THE STRENGTH OF BOLTED JOINTS IN [0/± ±45/90] S GFRE COMPOSITES
Conference Paper
Full-text available
  • Dec 2004
The weight and fuel savings offered by composite materials make the m attractive not only to the military, but also to the civilian aircraft, space, and automobile industries. In these industries, bolting and riveting are extensively used as a primary method of forming structural joints. Therefore, the main objective of the present paper is to investigate the influence of certain factors on the strength of bolted joints in [0/±45/90] s glass fiber reinforced epoxy (GFRE) composites. These factors include the tightening torque (T = 0, 5, 10 & 15 Nm) and the washer outer diameter size (Dwo = 14, 18, 22 & 27 mm). The mechanical properties (tensile, compressive, and in-plane shear) of GFRE laminates have been determined experimentally and theoretically. The experimental results show that under the same tightening torque, the slope of load-displacement diagrams of bolted joints (stiffness) increases with decreasing washer size. Bolted joint with 18 mm washer size and 15 Nm tightening torque has the maximum strength. In the range of the investigated tightening torques, the bearing strength of bolted joint with 18 mm washer size increases with increasing tightening torque. The load-displacement curve of bolted joint specimen with finger tight, T=0 Nm, has the lowest slope/stiffness with several knees, which may indicate an unstable development of internal damage. Most of the test specimens failed in the following sequence: (a) delamination between the 0 o , ±45 o , and 90 o layers due to their different strains under the compressive bearing load, (b) net tension failure mode for 90 o layers, (c) shear-out failure modes for 0 o layers, and (d) the final failure was nearly catastrophic due to the bearing failure of ±45 o layers.
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... Scores of parameters can affect the mechanical properties of joint structures, such as joining method, clearance, pin-elasticity, clamping torque and washers etc. On account of the significance of this problem, pin-loaded laminated composites have been studied experimentally and numerically [4][5][6][7]. However, little research about Excerpt from ISBN 978-3-00-053387-7 mechanical joint in chopped fiber tape material was conducted until now since it's an emerging material, but which is developing rapidly these years. ...
View
... These excellent properties of pitch fibers are transferred to matrix through their interface. Accordingly most of pitchbased carbon fibers reinforced composite properties are controlled by interfacial adhesion between pitch fibers and matrix resins [1,2]. ...
Influence of MWCNTs on Fracture Toughness of MWCNTs/Nickel-Pitch Fiber/Epoxy Composites
Article
  • Dec 2015
The influence of MWCNTs on fracture toughness properties of MWCNTs/Nickel-Pitch Fibers/epoxy composites (MWCNTs/Ni-PFs/epoxy) was investigated according to MWCNTs content. Nickel-Pitch-based carbon fibers (Ni-PFs) were prepared by electroless nickel-plating. The surface properties of Ni-PFs were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS). The fracture toughness of MWCNTs/Ni-PFs/epoxy was assessed by critical stress intensity factor (K_{IC}) and critical strain energy release rate (G_{IC}). From the results, it was found that the fracture toughness properties of MWCNTs/Ni-PFs/epoxy were enhanced with increasing MWCNTs content, whereas the value decreased above 5 wt.%. MWCNTs content. This was probably considered that the MWCNTs entangled with each other in epoxy due to an excess of MWCNTs.
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... This load reduction can lead to failure. Due to anisotropic and heterogenic nature of composites, these mechanically fastened joints are much more complicated for analysis than those made of isotropic materials; therefore, many authors studied strength of mechanically fastened composite joints [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Parameters such as joint geometry and fiber orientation, i.e. layers stacking sequence, have an important role in studying these structures. ...
Numerical Simulation of Composite Structure Failure in the Areas of Geometric Discontinuities
Article
The paper is directed to the failure analysis in layered composite structures with a special view on the impact of geometrical discontinuities on the stress level during which initial failure occurs. A special attention in the paper has been directed to the strength analysis of layered composite structures in the area of mechanically fastened joints. The emphasis of the paper is on establishing a suitable numerical procedure for the initial failure analysis of mechanically fastened joints of layered composites. To determine stress distribution around the hole, the finite element method (FEM) was used. The failure of a mechanically fastened joint was determined by combining the Chang-Scott-Springer model of the characteristic curve [1] and the Tsai-Wu initial failure criterion. The finite element model, which simulates the contact between the lug and the pin, was used for the analysis. The numerical results were compared to author's own experimental results where good agreement is obtained.
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View
The Effect of Stacking Sequence on the Pin-Bearing Strength in Glass Fibre Reinforced Plastic
Article
Full-text available
The pin-bearing strength of glass fibre reinforced plastic plates was measured using specimens possessing mid-plane symmetry and composed of eight layers, two each at 0° , 90° , and ±45° . The results suggest that placing the 90° layer (normal to the applied load) at or next to the surface increases the bearing strength. The ultimate failure mode was found to depend on stacking sequence.
View
View
Comparative assessment of bolted joints in a graphite reinforced thermoset vs. thermoplastic
Article
  • Jul 1989
In this study, bearing strength in a graphite reinforced thermoplastic, AS4/PEEK, and a graphite reinforced epoxy, IM6/3501-6, determined in order to make a comparative assessment of bolted joints in the two systems. AS4/PEEK, showed superior bolted joint performance to IM-6/3501-6 for the quasi-isotropic and cross-plied laminated. The test geometry with a single bolt symmetric double lap is the most consistent for the evaluation of bolted joints.
View
Elevatation of Bearing Strength on Mechanically Fastened Carbon/Epoxy Joints by Thermoplastic Film Stacking
Article
  • Nov 1991
Bearing strength is most important factor for designing the mechanical joints. Bearing failure is occurred by stress concentration around a hole. It is thought that bearing strength will be elevated by decreasing the stress concentration. In this study, we examined elevatation of bearing strength by thermoplastic film stacking into quasi-isotropic T800/#2500 joints. AE technique was used to investigate failure mechanism and kaiser effect test was performed to investigate the healthiness of materials. We determined that bearing strength was maximum stress during kaiser effect was valid. As a results, it was cleared that the healthiness of specimen was elevated by film stacking. Therefore, it is thought that film stacking is effective for designing mechanical joints. We calculated the shear stress distribution to investigate the influence of film by FEM. As a result, it was made sure that stress concentration was decreased by film.
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On the bearing strength of CFRP laminates
Article
  • Jul 1982
  • Composites
Bearing strength measurements have been made on 0° ±45°, 0° 90° and 90° ±45° cfrp laminates made from three different fibre/resin systems; HTS/914, XAS/914 and HTS/HC 3501. Equations have been derived for predicting the ultimate bearing strengths of constrained pin-loaded holes using a semi-empirical approach, and considering the physical conditions governing failure at the hole edge. Experimental results are presented and these show good agreement with those predicted for each of the laminate configurations and fibre/resin systems used.
View
Determination of safety factors for use when designing bolted joints in grp
Article
  • Apr 1979
  • Composites
Tests on single-hole bolted joints in glass reinforced epoxy and polyester laminates have indicated that significant damage occurs when the hole elongates by about 0.4% of the original diameter. Using this as a definition of limit load suggests employing an ultimate safety factor of 2.0 in design calculations.
View
Behavior of Kevlar 49 fabric/epoxy laminates subjected to pin bearing loads
Article
  • Apr 1977
The low compressive strength of Kevlar reinforced composites causes concern about the ability of these materials to withstand bearing loads in bolted joints. This paper presents the results of an experimental investigation of the pin bearing load-deflection response of (0/90/+-45), (0/90) and (+-45) Kevlar 49 fabric/epoxy laminates. Laminate thicknesses from 0.075 in. to 0.300 in. were examined for pin diameters ranging from 0.125 in. to 0.500 in. Results of this study revealed three significant points: (1) a synergistic effect takes place in the (0/90/+-45) ply stacking sequence which results in higher yield and ultimate strengths than the (0/90) and (+-45) laminates; (2) bearing strength varies inversely with pin diameter, probably due to the statistical strength behavior of these materials; and (3) nominal bearing yield strengths are very low (10 to 20 ksi). It is concluded that joint designs should incorporate local reinforcement in bolted or pinned areas.
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The bolt bearing strength of glass/carbon hybrid composites
Article
  • Jul 1982
  • Composites
Tests on single bolt joints in 0/90° hybrid laminates show that the bearing behaviour is similar to that of other types of fibre-reinforced plastic. Bearing strength varies with carbon content in a similar way to tensile strength. All-glass and hybrid materials fail in a ‘ductile’ fashion, whereas all-carbon material shows a more brittle failure.
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The effect of clamping pressure on bolt bearing loads in glass fibre-reinforced plastics
Article
  • Jan 1976
  • Composites
Bolt bearing failure modes in fibre-reinforced composite materials are a mixture of compressive and delamination failure at the bolt hole. The current work shows that, in grp with a 0/90° lay-up, the clamping effect of the bolt prevents the delamination with consequent increase in failure load.
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The Strength of Bolted Joints in Multi-Directional CFRP Laminates
Article
  • Jan 1977
  • Composites
Tests have been carried out on simple bolted joints in multi-directional cfrp for a range of laminate configurations and hole sizes. For single-hole joints the various modes of failure have been isolated and the corresponding strengths measured; the effects of variables such as ply orientation, laminate thickness and bolt clamping pressure are discussed in the light of the results. Multi-hole joints have been designed using the single-hole data and test results show that for normal bolt spacings there is little interaction between holes. The results also show that the specific static strengths of these joints can be significantly better than those in conventional materials such as aluminium alloy and steel.
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