Experimental studies conducted on a particular cast acrylic composite demonstrate the significant influence of the interfacial bond strength between filler particles and the polymer matrix on the fatigue life, and mechanical properties. The composite studied in this project is composed of a ductile matrix, which is lightly cross-linked poly-methyl methacrylate (PMMA) and hard, brittle alumina trihydrate (ATH) agglomerate particle filler. In the study, high, moderate, and low levels of interfacial adhesion between the matrix and the filler are investigated, while all the other material properties are kept constant. Monotonic tension and fatigue tests are conducted at different temperatures. Material degradation is presented in terms of elastic modulus degradation, load-drop parameter, and plastic strain range.

Acrylic casting dispersion is used to fabricate particulate composites such as poly-methyl methacrylate (PMMA) filled with a fine dispersion alumina trihydrate (ATH). This composite is subjected to severe temperature variations during in-service conditions, giving rise to high thermal stresses which lead to failure by cracking. The influence of the interfacial bond strength between a particle and the matrix on the failure mechanism of acrylic casting dispersion has been investigated using in situ observations during tensile and compressive loadings. Experiments show that the failure in pure tension occurs differently than in flexure loading where the failure process is believed to be more complex. During tensile loading, it is observed that macroscopic fracture is initiated in the clusters of the reinforcing particles because of the strong interfacial bonding strength between the filler particles and matrix. For weak interfacial bond strength, the macroscopic fracture is initiated by separation of filler agglomerates from the matrix.

Monotonic tensile tests are conducted on seven different Glare grades of fiber metal laminates. In-situ stress-strain curves of glass/epoxy laminate interleaved in Glare 2(3/2) are exposed with the application of metal volume fraction method using the stress-strain curves of Glare 2(3/2) and Aluminum 2024-T3 in unidirectional and transverse directions. The strain-stress curves of cross-ply Glares are predicted by the modification of this method with an empirical parameter and a second parameter considering the relative glass/epoxy laminate thickness ratios of Glare grades. Modified metal volume fraction method presented in this study can be used as a preliminary estimation of stress-strain curves of multiple possible fiber metal laminate configurations without testing.

An experimental study was conducted to sense interlaminar delamination in carbon-fiber composites utilizing inherent material piezoresistivity. Mode I and II interlaminar fracture tests were carried out on double cantilever beam and end-notched-flexure specimens following ASTM standards. The traditional DC-sourcing two-point probe technique was employed to measure the through-thickness electrical resistance change. For comparison, optical marker method and acoustic emission technique were also applied to detect interlaminar crack growth. The investigation demonstrates the application potential of the self-sensing capabilities of carbon-fiber composites for structural health monitoring.

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