Fiber-Matrix Adhesion and Its Effect on Composite Mechanical Properties: II. Longitudinal (0°) and Transverse (90°) Tensile and Flexure Behavior of Graphite/Epoxy Composites

Abstract

East Lansing. MI 48824 (Raeivod December 12. B89) (Revised Augur1 21. 1990)AB!TlXACl': An optimum level of interfacial bond strength between reinforcing fiber and a polymeric matrix in which it is placed is essential for acceptable composite mechanical properties and performance. The interfacial bond strength can be optimized only when the relationship between the level of fiber-matrix adhesion and thc mechanical and fracture behavior of composites is clearly understood. This study establishes the relationship between the fiber-matrix interfacial shear strength and 0" and 9 0 ' tensile and flexure p r o p t i e s of graphitdepoxy composites. A well defined and characterized graphite fiberlepoxy system was chosen in which the level of adhesion between fiber and matrix Mas changed by using the same gmphite fibers through the use of surface treatment and finish. The level of adhesion between the fiber and matrix associated with these changes resulted in an increase of fiber-matrix interfacial shear strength (ISS) by Over a factor of tvm while the fiber and matrix properties remained unchanged. The experimental results demonstrated that thc fiber surface modification did not have much effect on the tensile and flexural moduli and on the fiber dominated properties. However, the strengths and maximum strains that are governed by the matrix and interface properties were highly sensitive to the fiber surface modification. In addition, the major failure modes were also found to be affected by the fiber-matrix interfacial shear strength. 1. BACKGROUND HE SENSITIVITY OF the mechanical behavior of composite materials to the T fiber-matrix interfacial bond strength has long been realized [l-31. Longitudinal tensile failure of carbon fiber composites having low interfacial bond strength displays a broom-like fracture surface, while those having a high interfacial bond display a brittle fracture surface [4,5]. It has been qualitatively known 95 8 Joiiriial Of COhfPOSlTE MATERIALS, k' d. 25-Altgltst 1991

Improving the interfacial and mechanical properties of short glass fiber/epoxy composites by coating the glass fibers with cellulose nanocrystals

“…In addition, the tensile strength increased for 1S-30GF/epoxy (~10%) and 1.5S-30GF/ epoxy composites with respect to that of 30GF/ epoxy composites. This increase reflects the higher IFSS (see Figure 2) inferring stronger interfacial interactions and better stress transfer across the fiber/CNC/epoxy interphase as also reported elsewhere [35]. The tensile strength of the 2S-30GF/epoxy composite was ~12% lower despite having higher IFSS compared to that of 30GF/epoxy.…”

Experimental optimization of the impact energy absorption of epoxy–carbon laminates through controlled delamination

“…In fact, the observed behaviour is consistent with the existing literature on the effects of fibre-matrix adhesion on the quasi static tensile and flexural mechanical properties of epoxy/graphite unidirectional composites. As reported by Madhukar and Drzal [50] and by Deng and Le [29] the fibre surface modification do not have much effect on the tensile and flexural moduli and on the fibre dominated properties. However, the strengths and the maximum strains, that are governed by the matrix and interface properties, are highly sensitive to the fibre surface modification.…”

Validating the Classical Failure Criteria for Applicability to the Notched Woven-Roving Composite Materials

“…The debond between the fiber filaments and matrix was clear. The justification for this is that the load is mainly transferred by the interfacial region between the fiber and matrix and the existence of shear stress component 6 [1,[15][16][17][18]. Another attestation for our interpretation is the X-radiograph taking a graphite-epoxy [0 2 /90 2 ] s laminate having a center notch by Binienda et al [34].…”

“…P u p p o a n d E v e n s e n [ 25] ( ] is the global of 45 ∘ tenstion test (1) Main frame (2) Main shaft (3) Self-aligning bearing (4) Bending loading arm (5) Bending transducer (7) Torque transducer (8) Intermediate shaft (9) Deep groove ball bearing (10) Guide shaft (11) Twisting moment arm (6) Specimen (13) Twisting moment coupling (12) Bending connecting rod (14) Coupling shaft (15) Driven pully (16) Twisting moment loading arm (17) Bending moment loading arm (19) Motor table (20) V belt (21) Bending coupling plain specimen, the observed failure mode was a matrix-cracking mode normal to the loading axis and along the transverse fiber direction as shown in Figure 10. This may be attributed to brittleness of the matrix compared to the filling fiber fabrics.…”

“…They also proposed an optimization of fiber coating procedure to reduce the stress concentration at the fiber matrix interaction locations. At the macrolevel scale, Madhukar and Drazal [15][16][17][18] published a series of papers describing the considerable effect of the interphase/interface on macrolevel strength and stiffness properties.…”