TY - JOUR
T1 - Mechanical Response and Fracture of Pultruded Carbon Fiber/Epoxy in Various Modes of Loading
AU - Bussiba, Arie
AU - Gilad, Ilan
AU - Lugassi, Snir
AU - David, Sigal
AU - Bortman, Jacob
AU - Yosibash, Zohar
N1 - Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2022/6
Y1 - 2022/6
N2 - Pultrusion is a continuous process of forming constant cross-sections of unidirectional composites with a significant long length. This unique process is implemented widely in the composites industry due to its continuous, automated, and highly productive nature. The current research focused on mechanical response characterization at three modes of loading: tensile, compression, and shear loading of coupons made from a graphite/epoxy 1 mm sheet. In addition, the effects of holes and notches were examined in terms of mechanical properties. The mechanical behavior was assessed through stress–strain curves with careful attention on the curve profile, macroscopic fracture modes observations, and optical microscopic tracking with continuous video records. The mechanical tests follow standards with some critiques on the shear test. Finite element analysis (FEA) was used to accurately determine the shear modulus, and for other mechanical investigations. By nature, under tension, the unidirectional fiber composite at 0° orientation exhibits high strength (2800 MPa), with very low strength at 90° orientation (40 MPa). Both orientations display linear mechanical behavior. Under compression, 0° orientation exhibits low strength (1175 MPa), as compared to tension due to the kinking phenomena, which is the origin in the deviation from linear behavior. Under shear, both orientations exhibit approximately the same shear strength (45 MPa for 0° and 47 MPa for 90°), which is mainly related to the mechanical properties of the epoxy resin. In general, in the presence of holes, the remote fracture stress in the various modes of loading did not change significantly, as compared to uniform coupons; however, some localized delamination crack growth occurred at the vicinity of the holes, manifested by load drops up to the final fracture. This behavior is also attributed to the tension of notched coupons. FEA shows that the shear values were unaffected by manufacturing imperfections, coupon thickness, and by asymmetrical gripping up to 3 mm, with minor effect in the case of a small deviation from the load line. Selected experimental tests support the FEA tendencies.
AB - Pultrusion is a continuous process of forming constant cross-sections of unidirectional composites with a significant long length. This unique process is implemented widely in the composites industry due to its continuous, automated, and highly productive nature. The current research focused on mechanical response characterization at three modes of loading: tensile, compression, and shear loading of coupons made from a graphite/epoxy 1 mm sheet. In addition, the effects of holes and notches were examined in terms of mechanical properties. The mechanical behavior was assessed through stress–strain curves with careful attention on the curve profile, macroscopic fracture modes observations, and optical microscopic tracking with continuous video records. The mechanical tests follow standards with some critiques on the shear test. Finite element analysis (FEA) was used to accurately determine the shear modulus, and for other mechanical investigations. By nature, under tension, the unidirectional fiber composite at 0° orientation exhibits high strength (2800 MPa), with very low strength at 90° orientation (40 MPa). Both orientations display linear mechanical behavior. Under compression, 0° orientation exhibits low strength (1175 MPa), as compared to tension due to the kinking phenomena, which is the origin in the deviation from linear behavior. Under shear, both orientations exhibit approximately the same shear strength (45 MPa for 0° and 47 MPa for 90°), which is mainly related to the mechanical properties of the epoxy resin. In general, in the presence of holes, the remote fracture stress in the various modes of loading did not change significantly, as compared to uniform coupons; however, some localized delamination crack growth occurred at the vicinity of the holes, manifested by load drops up to the final fracture. This behavior is also attributed to the tension of notched coupons. FEA shows that the shear values were unaffected by manufacturing imperfections, coupon thickness, and by asymmetrical gripping up to 3 mm, with minor effect in the case of a small deviation from the load line. Selected experimental tests support the FEA tendencies.
KW - compression
KW - delamination crack growth
KW - kinking
KW - pultrusion
KW - shear
KW - tension
KW - unidirectional laminate composites
UR - http://www.scopus.com/inward/record.url?scp=85132570009&partnerID=8YFLogxK
U2 - 10.3390/cryst12060850
DO - 10.3390/cryst12060850
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AN - SCOPUS:85132570009
SN - 2073-4352
VL - 12
JO - Crystals
JF - Crystals
IS - 6
M1 - 850
ER -