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Investigation of the Fiber Reinforced Laminates Stiffness Reduction Due to Internal Defects and Matrix Cracks



Internal defects and matrix cracks in the polymer matrix of fiber reinforced composites are often treated the same. The analytical and numerical damage modeling techniques apply the same degradation coefficients in the transverse and shear direction independent of the damage source. While the transverse stiffness reduction is similar for cracks and internal defects, the shear modulus degradation is different. A modified Iosipescu coupon was used in this study to investigate the transverse and shear modulus reduction due to cracks and internal defects. Transverse cracks had a greater effect on the transverse modulus than the shear modulus. It was shown that the difference in the transverse and shear direction was due to the roughness of the crack surfaces.

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