Materiales.Compuestos at 17:40, 20 October 2022

2022-10-20T17:40:25Z

Scipediacontent at 08:07, 3 May 2022

2022-05-03T08:07:16Z

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Scipediacontent: Scipediacontent moved page Draft Content 735980890 to Llobet et al 2018a

2022-03-31T18:36:06Z

Scipediacontent moved page Draft Content 735980890 to Llobet et al 2018a

Scipediacontent: Created page with "== Abstract == Fibre-reinforced composite materials can withstand large number of loading cycles compared to traditional materials. However, predicting the damage progress an..."

2022-03-31T18:36:03Z

Created page with "== Abstract == Fibre-reinforced composite materials can withstand large number of loading cycles compared to traditional materials. However, predicting the damage progress an..."

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== Abstract ==

Fibre-reinforced composite materials can withstand large number of loading cycles compared to traditional materials. However, predicting the damage progress and strength loss in a composite structure due to fatigue is difficult because of the complex interaction of different failure mechanisms.
This work investigates the decrease in the stiffness and strength in a high-performance undirectional CFRP laminate subjected to on-axis fatigue loads. A stiffness-based phenomenological model is proposed in order to evalute the damage growth due to fatigue through the longitudinal stiffness degradation.
Assuming that the laminate ultimate strain is independent of the distributed damage caused by fatigue, the residual strength model can be deduced, or its integral form, the S-N curve. Thanks to this assumption, the residual stiffness model is related to the residual strength model, and thus it has reduced the experimental characterization of phenomenlogical-based approaches. The accuracy of the model is verified by comparing the experimental data against the derived S-N curves.

== Full document ==
<pdf>Media:Draft_Content_735980890native-articles-180.pdf</pdf>

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 ==1 Introduction==
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 Figure 1 shows the fitted functions and the experimental data obtained for different stress levels and constant stress ratio ''K.'' The red crosses illustrate the assumed failure point for each test ''d=1- Σ<sub>max.</sub>'' For stress levels Σ<sub>max</sub><0.5, the stiffness loss seems to be negligible up to 2 million cycles. Nevertheless, many specimens failed in the tabbed section for stress levels Σ<sub>max</sub>>0.75. These premature failures lead to an underestimation of fatigue life which should be interpreted carefully. Figure 2 depicts how fatigue life increases with the increase in the stress ratio ''K'' when the peak stress is kept constant. The best least square fitting for equation (3) is: ''c<sub>1</sub>=''750'', c<sub>2</sub>=''22'', c<sub>3</sub>=''16'' and c<sub>4</sub>=''4.
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 <div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 <span style="text-align: center; font-size: 75%;">'''Figure 1. '''Damage function vs. loading cycles for different stress levels and constant stress ratio ''K''=1.22.</span></div>
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 <div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 2. '''Damage function vs. loading cycles for different stress ratios ''K'' and constant stress </span>Σ<sub>max</sub><span style="text-align: center; font-size: 75%;">.</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 2. '''Damage function vs. loading cycles for different stress ratios ''K'' and constant stress </span>Σ<sub>max.</sub></div>
 The assumption of a constant ultimate strain is appropriately validated in Figure 3. After some of the performed fatigue tests, the specimens were tested quasi-statically until failure and the ultimate strain was measured. If this residual strain is within the scatter of the ultimate static strain (red crosses), the hypothesis is admissible.
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 Finally, the experimental fatigue lives and the life predictions are compared in Figure 4.
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Llobet et al 2018a - Revision history

Materiales.Compuestos at 17:40, 20 October 2022

Scipediacontent at 08:07, 3 May 2022

Scipediacontent: Scipediacontent moved page Draft Content 735980890 to Llobet et al 2018a

Scipediacontent: Created page with "== Abstract == Fibre-reinforced composite materials can withstand large number of loading cycles compared to traditional materials. However, predicting the damage progress an..."