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Based on Christen sen and Lo's (11) three‐layer sphere model, a two‐layer built‐in model is proposed to represent particulate‐filled composites. Following Papanico‐laou and Bakos' (14) procedure for a particle embedded in an infinite matrix model and using the rule‐of‐mixtures approach, formulations estimating the tensile strength of particulate‐filled composites are developed. Unlike Fapanicolaou and Bakos' formulations, the formulations developed in the present paper can characterize the effect of particle size, particle size distribution, and particle clustering on the tensile strength of the composites. A reasonable agreement is found between the predicted tensile strength and the experimental results found in the literature. Parameters affecting the tensile strength of particulate‐filled composites are discussed via the calculated results.

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The low velocity impact response of laminated composites in ambient hygrothermal environments has been extensively investigated. This response, however, is not well understood when subjected to moisture cycling at elevated temperatures. In this current study, two types of glass fiber reinforced plastic (GFRP) laminates, unidirectional and crossply, were conditioned in a conditioning chamber for a maximum of eight moisture cycles at conditioning temperatures from 50°C to 100°C. Low velocity impact tests were conducted on the conditioned specimens and control specimens via an instrumented drop‐weight impact testing machine. The tension after impact (TAI) strength was investigated using an MTS machine. The equivalent damage size is obtained using an average stress criterion found in the literature. The effect of moisture cycling and conditioning temperatures on the low velocity impact response and residual load carrying capacity of GFRP laminates are evaluated via the test results.