Autonomic Recovery of Fiber/Matrix Interfacial Bond Strength in a Model Composite

Abstract

animals achieve material stasis via highly sophisticated autonomic repair and regenerative responses triggered by damage.Self-healing in synthetic materials has been demonstrated using a variety of methods such as incorporation of healingagent-fi lled capsules (capsule-based), [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] interconnected vascular networks [ 16 , 17 ] or discrete hollow capillaries, [18][19][20][21] or utilizing intrinsic properties of the material. [22][23][24][25][26] Capsule-based self-healing has been demonstrated in bulk thermoset matrices, [1][2][3][4][5][6][7][8][9] fi ber reinforced composite materials [10][11][12][13][14] and elastomers. [ 15 ] In these materials, damage triggers the rupture of the embedded capsules, releasing healing agent into the damaged material through capillary action. Polymerization of the healing agent is initiated by contact with an embedded catalyst or secondary polymerizing liquid.Efforts to develop self-healing fi berreinforced composites have focused on repair of large-scale delaminations and matrix cracking, but little attention has been given to repair of other composite damage modes. Complex damage modes in fi ber-reinforced composites such as matrix cracking, delamination, fi ber debonding, and fi ber rupture [ 27 , 28 ] present challenges beyond those addressed by self-healing in bulk polymers. In particular, debonding of the reinforcement from the matrix leads to a signifi cant loss of strength and stiffness of the composite by preventing effi cient load transfer from fi ber to matrix. [ 29 ] Additionally, small-scale damage, which may initiate at interfacial defects, can coalesce into large-scale damage during fatigue, ultimately leading to failure of the composite.Fiber-matrix adhesion is characterized by a variety of testing methods including single-fi ber pull-out and microbond, [30][31][32][33][34] single-fi ber fragmentation, [35][36][37][38][39] and single-fi ber pushout tests. [40][41][42][43][44] Each of these single-fi ber tests enables the measurement of the interfacial shear strength (IFSS, τ ) between the fi ber and matrix. In this work, the single-fi ber microbond specimen is adopted for assessing the ability to heal interfacial damage and recover IFSS. Microbond samples consist of a single fi ber embedded in a droplet or cylindrical block of matrix material ( Figure 1 ) and were prepared in a manner similar to the fl at cylindrical specimens described by Zhandarov et al. [30][31][32][33][34] During testing of a microbond specimen, the matrix is constrained and stress is transferred to the matrix-reinforcement interface by pulling on the embedded fi ber, which eventually leads to debonding. [30][31][32][33][34] Autonomic Recovery of Fiber/Matrix Interfacial Bond Strength in a Model CompositeAutonomic self-healing of interfacial damage in a model single-fi ber composite is achieved through sequestration of ca. 1.5 μ m diameter dicyclopentadiene (DCPD) healing-agent-fi lled capsules and recrystallized Grubbs' catalyst to the fi ber/m...

Silica‐Protected Micron and Sub‐Micron Capsules and Particles for Self‐Healing at the Microscale

“…Finally, new testing methods are needed to evaluate healing at smaller size-scales. Recovery of interfacial shear strength was recently demonstrated for micron size capsule-functionalized glass fibers [10] in an epoxy matrix, but evaluation of small size-scale self-healing in bulk polymers remains a challenge. In this research, each challenge is addressed in order to develop a strong framework for future self-healing at smaller size-scales.…”

“…In fiber-reinforced composites, the spacing between fibers is often well below a micron. [10] Similarly, for thin film applications, polymer films are often only micrometers thick. In both of these cases, self-healing components must fit into the space available.…”

Thermoreversible and remendable glass–polymer interface for fiber-reinforced composites

“…Following impact damage, total recovery of strength was observed. Fiber-resin interfacial healing has been previously demonstrated by placing resinfilled nanocapsules and catalyst (if necessary to induce polymerization) on a fiber surface [26]. Upon failure, capsules rupture and the polymer fills and cures in the crack site, resulting in recovery of 44 ± 5% in interfacial shear strength for the most effective system.…”

Preparation and assessment of a self‐healing material based on microcapsules filled with ethyl phenylacetate

“…Several materials can be used as healing agents on the basis of their different healing chemistries; these include dicyclopentadiene, [12][13][14][15][16] vinyl terminated poly(dimethyl siloxane) resin, 17,18 epoxy resins, [19][20][21][22][23][24] and solvents. [25][26][27][28][29] Compared with other healing systems, the solvent-promoted self-healing system is a simple, one-component, less expensive, and highly efficient system because of the absence of catalysts. Although crack healing in thermoplastics has been investigated primarily because of the diffusion of chains across the interface, [30][31][32] the healing mechanism of a thermoset based on a solvent remains unclear.…”