Kinematic hardening rules with critical state of dynamic recovery, part I: formulation and basic features for ratchetting behavior

A review: Fibre metal laminates, background, bonding types and applied test methods

Composites science and technology

Weight reduction and improved damage tolerance characteristics were the prime drivers to develop new family of materials for the aerospace/aeronautical industry. Aiming this objective, a new lightweight Fiber/Metal Laminate (FML) has been developed. The combination of metal and polymer composite laminates can create a synergistic effect on many properties. The mechanical properties of FML shows improvements over the properties of both aluminum alloys and composite materials individually. Due to their excellent properties, FML are being used as fuselage skin structures of the next generation commercial aircrafts. One of the advantages of FML when compared with conventional carbon fiber/epoxy composites is the low moisture absorption. The moisture absorption in FML composites is slower when compared with polymer composites, even under the relatively harsh conditions, due to the barrier of the aluminum outer layers. Due to this favorable atmosphere, recently big companies such as EMBRAER, Aerospatiale, Boing, Airbus, and so one, starting to work with this kind of materials as an alternative to save money and to guarantee the security of their aircrafts.

/pdf/a-review-on-the-development-and-properties-of-continuous-54nax2ejil.pdf

A review on the development and properties of continuous fiber/epoxy/aluminum hybrid composites for aircraft structures

GLARE (glass-reinforced aluminum laminate) is a new class of fiber metal laminates for advanced aerospace structural applications. It consists of thin aluminum sheets bonded together with unidirectional or biaxially reinforced adhesive prepreg of high-strength glass fibers. GLARE laminates offer a unique combination of properties such as outstanding fatigue resistance, high specific static properties, excellent impact resistance, good residual and blunt notch strength, flame resistance and corrosion properties, and ease of manufacture and repair. GLARE laminates can be tailored to suit a wide variety of applications by varying the fiber/resin system, the alloy type and thickness, stacking sequence, fiber orientation, surface pretreatment technique, etc. This article presents a comprehensive overview of the mechanical properties of various GLARE laminates under different loading conditions.

The mechanical behavior of GLARE laminates for aircraft structures

A phenomenological fatigue model is developed for the off-axis fatigue behavior of a class of unidirectional polymer matrix composites subjected to constant-amplitude stress cycling with non-negative mean stresses. For this purpose, a new non-dimensional effective stress that considers the effects of the stress ratio and multiaxial state of stress on the off-axis fatigue behavior of unidirectional composites is defined for the range of non-negative mean stresses. Non-dimensional effective stress is used as the strength measure to characterize the brittle nature of the evolution of fatigue damage. This allows one to obtain a practical form of multiaxial fatigue model that takes into account the fiber-orientation dependence as well as the mean-stress dependence of the off-axis fatigue behavior of unidirectional composites. The constant-fatigue life diagram predicted by the proposed fatigue model is described in terms of a normalized relation of the modified Goodman type. It is demonstrated that the off-axis S – N relationships for unidirectional carbon/epoxy and glass/epoxy composites are adequately described using the proposed fatigue model over the range of non-negative mean stresses.

A phenomenological model for off-axis fatigue behavior of unidirectional polymer matrix composites under different stress ratios

Exploration of a full shape of constant fatigue life (CFL) diagram and development of an efficient CFL diagram-based fatigue life prediction method are attempted for multidirectional CFRP laminates. On three kinds of CFRP laminates of [45/90/−45/0]2s, [0/60/−60]2s and [0/90]3s lay-ups, tension–tension, tension–compression and compression–compression fatigue tests are performed at room temperature for two different stress ratios each. Experimental results clearly show that a stress ratio has a significant influence on the fatigue behavior of those CFRP laminates, and the CFL diagrams delineated using alternating stress and mean stress become asymmetric about the alternating stress axis. The alternating stress component of fatigue load for a given constant value of fatigue life turns maximum in the case of fatigue loading at a critical stress ratio that is nearly equal to the ratio of compressive strength to the tensile one. The shape of CFL diagrams progressively changes from a straight line to a nonlinear curve as a given constant value of fatigue life increases. A new and efficient method for accurately predicting an asymmetric nonlinear CFL diagram is then developed which is based on the static strengths in tension and compression and the reference S–N relationship fitted to the fatigue data for the critical stress ratio. The theoretical CFL diagram constructed following the proposed procedure agrees well with the experimental CFL diagram, regardless of the type of CFRP laminate. It is also demonstrated that the S–N relationships predicted using the proposed CFL diagram-based fatigue life prediction method adequately coincide with the experimental results for fatigue loading with a variety of different stress ratios in the range of fatigue life up to 106 cycles.

Nonlinear constant fatigue life diagrams for carbon/epoxy laminates at room temperature

High-temperature off-axis fatigue behaviour of unidirectional carbon-fibre-reinforced composites with different resin matrices

Off-axis fatigue behavior of a plain-woven carbon/epoxy fabric laminate at room temperature and 100 °C has been studied. Tension–tension fatigue tests are first performed on plain coupon specimens with five kinds of fiber orientations θ =0, 15, 30, 45, 90° at a frequency of 10 Hz in respective temperatures. Test results show that the fatigue behavior of the carbon fabric laminate significantly depends on fiber orientation. The on-axis S – N relationships plotted on logarithmic scales are almost linear over the range of fatigue life up to 10 6  cycle. By contrast, the off-axis S – N relationships are characterized by their S-shape. The log–log plot of the off-axis fatigue data becomes steeper in an intermediate range of fatigue life than before, suggesting increased sensitivity to fatigue, and it subsequently reaches a plateau indicating an apparent fatigue limit. The fiber orientation dependence of the off-axis fatigue strength can substantially be removed by normalization with respect to a modified static strength. These features are common to the fatigue behaviors at room temperature and 100 °C. Additional fatigue tests with a frequency of 2 Hz demonstrate that the shape of the off-axis S – N curve at room temperature is significantly affected by load frequency, as a result of a different specimen heating. Comparison between the high-temperature fatigue data at 2 and 10 Hz reveals that the S-shape of the off-axis S – N curve is caused partly by an intrinsic rate dependence of the carbon fabric laminate. Applicability of a phenomenological fatigue model that considers the effect of fiber orientation and of multiaxial state of stress is also examined for description of the off-axis fatigue behavior at 10 Hz. The results illustrate that the fatigue model can be used for describing the off-axis fatigue behavior of the carbon fabric laminate at room temperature and 100 °C for a given frequency of fatigue loading.

Off-axis fatigue behavior of plain weave carbon/epoxy fabric laminates at room and high temperatures and its mechanical modeling

Influences of non-negative mean stress on the off-axis fatigue behavior of unidirectional composites are elucidated on the basis of a non-fragmentary set of data on the T800H/2500 carbon/epoxy lami...

Masamichi Kawai

Papers

A phenomenological model for off-axis fatigue behavior of unidirectional polymer matrix composites under different stress ratios

Nonlinear constant fatigue life diagrams for carbon/epoxy laminates at room temperature

High-temperature off-axis fatigue behaviour of unidirectional carbon-fibre-reinforced composites with different resin matrices

Off-axis fatigue behavior of plain weave carbon/epoxy fabric laminates at room and high temperatures and its mechanical modeling

Effects of Non-Negative Mean Stress on the Off-Axis Fatigue Behavior of Unidirectional Carbon/Epoxy Composites at Room Temperature