Abstract
The effect of scratch damage on the tension properties of carbon fiber plain weave laminates has been studied in detail using digital image correlation (DIC) and acoustic emission (AE). A range of scratch lengths was machined onto different laminates. The bearing capacity of the laminates was then compared with that of unaltered samples. The strain field distributions near the scratches were measured and analyzed as a function of scratch length with DIC. Initiation and propagation of damage were monitored during the tensile tests using AE. Failure sites and morphologies were observed and analyzed. The results show that superficial scratches have little effect on the strength of plain weave laminates when the scratch length is less than 80% of the specimen width. Scratches affect the distribution of strain near the scratch but not far away from the scratch or at the back face of the sample. Not all samples broke from the scratch site but instead broke from the free edge of the sample or close to the gripping region.
Highlights
Composite materials are increasingly used for many important applications in industry, especially in aerospace. is is due to their significantly higher strength, stiffness, and versatile design
digital image correlation (DIC) measurements were used to determine the full-field strains at different points in the loading regime, by tracking random speckle patterns on the scratched specimens. ree strain gauges were mounted at points A, B, and C (Figure 2(c)) on the scratched back face and two acoustic emission (AE) sensors were mounted on the back face of the sample to monitor damage initiation and propagation
Several conclusions could be drawn from these experiments: (1) e effect of superficial scratches was insignificant in terms of tensile strength when the scratch length was small
Summary
Composite materials are increasingly used for many important applications in industry, especially in aerospace. is is due to their significantly higher strength, stiffness, and versatile design. Is is due to their significantly higher strength, stiffness, and versatile design. Despite these desirable properties, composite structures are susceptible to defects during both manufacturing and in service. Several studies of damage to composites have focused on the response and performance of composite structures that have been subjected to low- or high-velocity impact [5,6,7,8]. Superficial cracks and/or scratches in composite materials may occur, for example, from concrete or other runway debris during aircraft takeoffs and landings. Is type of damage can eventually degrade static strength and fatigue strength of the composite structure, making the laminates with scratches more vulnerable to failure under an external load Scratches can cut into the fibers of some of the plies, which can in turn induce high interlaminar stress and stress concentration. is type of damage can eventually degrade static strength and fatigue strength of the composite structure, making the laminates with scratches more vulnerable to failure under an external load
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