Gives the procedure for the preparation of test plates or panels by bonding glass cloth or mats with low-pressure thermosetting resins which cure at or above room temperature either without loss of reaction products or which are not significantly altered by loss of reaction products during cure and which can be processed with a pressure up to 3,5 MPa. Standardizes the preparation of the plates or panels from which test specimens subsequently can be machined and specimens so prepared may be used either for evaluating the components; or for verifying the overall quality of the finished "composite" products.