Fiber-matrix interface studies on bioabsorbable composite materials for internal fixation of bone fractures. I. Raw material evaluation and measurement of fiber?matrix interfacial adhesion

Abstract

The objective of this study was to characterize and evaluate the performance of various fiber-matrix composite systems by studying the mechanical, thermal, and physical properties of the fiber and matrix components, and by studying the fiber-matrix interface adhesion strength using both microbond and fragmentation methods. The composites studies were poly(L-lactic acid) (PLLA) matrix reinforced with continuous fibers of either nonabsorbable AS4 carbon (C), absorbable calcium phosphate (CaP), poly(glycolic acid) (PGA), or chitin. Carbon and CaP single fibers had high Young's moduli and failed in a brittle manner. PGA and chitin single fibers had relatively lower Young's moduli and relatively higher ductility. Upon in vitro hydrolysis, CaP fibers retained 17% of their tensile strength and 39% of their Young's modulus after 12 h, PCA fibers retained 10% of their tensile strength and 52% of their Young's modulus after 16 days, and chitin fibers retained 87% of their tensile strength and 130% of their Young's modulus after 25 days. PLLA films had much lower strength and Young's moduli, but much higher ductility relative to the single fibers. Using the microbond method, the initial fiber-matrix interfacial shear strength (IFSS) of C/PLLA and CaP/PLLA microcomposites was 33.9 and 12.6 MPa, respectively. Upon in vitro hydrolysis, C/PLLA retained 49% of IFSS after 15 days and CaP/PLLA retained 46% of IFSS after 6 h. Using a fiber fragmentation method, the initial IFSS of C/PLLA, CaP/PLLA, and chitin/ PLLA was 22.2, 15.6, and 28.3 MPa, respectively. The performance of carbon fibers and C/PLLA composites was superior to the other fibers and fiber/PLLA systems, but the carbon fiber was nonabsorbable. CaP had the most suitable modulus of the absorbable fibers for fixing cortical bone fracture, but its rapid deterioration of mechanical properties and loss of IFSS limits its use. PGA and chitin fibers had suitable mechanical properties and their retention for fixing cancellous bone fractures, but likely had insufficient stiffness for applications such as bone plates for fixing cortical bone fractures.

Weight loss, ion release and initial mechanical properties of a binary calcium phosphate glass fibre/PCL composite

“…No significant improvement in strength was introduced via fibre reinforcement (25)(26)(27)(28)(29)(30). However, the modulus showed a fivefold increase at 18% V f (2.5 GPa).…”

“…The cellulose-based binding agent did not appear to contribute to the interface development, conferring no property improvements. No explicit measurements of interfacial shear strength (the conventional measure for interface efficiency) are presented here, but preliminary results for a similar fibre-matrix combination were published by Slivka et al [27], confirming the above assertions with IFSS values of approximately 15 MPa for CaP/PLLA, as compared to 23 MPa for carbon fibre PLLA single fibre composite specimens.…”

Mechanical, Degradation, and Interfacial Properties of Synthetic Degradable Fiber Reinforced Polypropylene Composites

“…The SFFT method has several advantages over the other methods, such as: simple specimen handling, replication of the stress transfer characteristics in real composites, convenient monitoring of failure processes directly and the fact that critical length is sensitive to the level of fiber-matrix adhesion. Interface scientists now regard this test as a mature method for the determination of interfacial properties of fiber reinforced composites [17][18][19][20][21].…”

Studies on the Relative Degradation and Interfacial Properties Between Jute/Polypropylene and Jute/Natural Rubber Composites

“…The SFFT method has several advantages such as simple specimen handling, replication of the stress transfer characteristics in real composites, and convenient monitoring of failure processes directly. Interface scientists termed this test as a reliable method for the determination of interfacial properties of the fiber reinforced polymer composites [21][22][23][24][25][26][27][28][29].…”