Micromechanical Analysis of Hybrid Composites

Abstract

The response of hybrid composites to tensile and transverse loads is studied using a micromechanical analysis. Of particular interest are the effects of matrix viscoelasticity and the properties of the interphase region on the material properties and failure initiation. The tensile response of hybrid composites is studied using a statistical model in which the fiber failure strains are represented with Weibull distributions. A shear lag formulation is used to include the contribution of load transfer to broken fibers to the longitudinal modulus. The transverse tensile response is studied using the rule-ofmixtures. Linear viscoelastic matrix properties are incorporated in both analyses. Results from the analysis indicate that the interphase properties have a negligible effect on the longitudinal failure strain and that the effect of matrix viscoelasticity on the longitudinal tensile response is negligible. The longitudinal failure strains decreased with increasing composite length and carbon to glass volume ratios. For transverse tensile loading, the stress rises more rapidly on the stress strain curve when the strain rate is increased and when the interphase moduli are higher.

Review of Composite Marine Risers for Deep-Water Applications: Design, Development and Mechanics

“…In the research by Venkatesan et al [252], carbonfibre-reinforced polymer (CFRP) composites were observed to have long-term qualities after being exposed to clean water and sea water at the same time, with noteworthy differences under various temperatures. Many researchers also concur with the finding that the CFRP's long-term tensile strength is lowered to between 80% and 95% of its original value in the short term [252][253][254][255][256][257][258]. It was also discovered in another study by Bismarck et al [58] on the evaluation of the carbon/PEEK thermoplastic composite that although its axial tensile strength was unaffected by boiling water, its transverse tensile strength was affected.…”

“…Similarly, the earlier study [200] revealed that the maximum VIV stress of a composite riser was substantially lower than that of a steel riser, demonstrating that composite risers have longer fatigue lifetimes. Likewise, Kim [98], Sun et al [255], Tan et al [226] and Toh et al [187] used different techniques like finite element method (FEM) to conduct thorough analyses on both local and global scales on composite and steel risers, finding higher safety factors for composite risers. However, the composite riser models without any VIV suppression exhibited mild fatigue damage.…”

“…Crack initiation is when a small crack appears at a high-stress-concentration location; fracture propagation is when the crack increases progressively with each stress cycle; and final failure is when the progressing crack reaches a critical size and fails quickly [333]. Hybrid composites improve composite functionality by allowing the designer to add selectivity, including stiffer, more-expensive fibres where stresses are more critical and less-expensive fibres where stresses are less critical [3,102,117,255]. As water depths have increased and service conditions have become more demanding, manufacturers of nonbonded flexible pipes are attempting to build pipe cross-sections incorporating carbon fibre parts to solve these concerns [342][343][344][345][346][347][348][349][350].…”